Fuel cell stop mode control method and control system

Abstract

The present invention provides a control method and a control system for a fuel cell stop mode. The method includes: measuring the air flow rate supplied to the fuel cell stack; and when entering the fuel cell stop mode, determining the oxygen distribution state between cells included in the fuel cell stack based on the measured air flow rate. Then, based on the determined oxygen distribution state, air is supplied to the fuel cell stack, or the air supply to the fuel cell stack is interrupted.

Description

Technical Field

[0001] The present invention relates to a control method and a control system for a fuel cell stop mode, and more particularly, to a technology for reducing a deviation between cell voltages in a fuel cell stop mode for stopping power generation of a fuel cell. Background Art

[0002] A fuel cell that converts chemical energy into electrical energy using a redox reaction between hydrogen and oxygen supplied from a hydrogen supply device and an air supply device, respectively, includes a fuel cell stack that generates electrical energy, a cooling system that cools the fuel cell stack, and the like. In other words, hydrogen is supplied to the anode of the fuel cell stack, an oxidation reaction of hydrogen is performed at the anode to generate protons and electrons, and the generated protons and electrons migrate to the cathode through an electrolyte membrane and a separator. In the cathode, the protons and electrons migrated from the anode react electrochemically with oxygen in the air to generate water, and electrical energy is generated according to the flow of electrons.

[0003] When the fuel cell stack is exposed to a high potential, the catalyst deteriorates, which worsens the irreversible degradation of the fuel cell stack, thereby reducing the overall performance. Therefore, in the fuel cell stack, the voltage of the fuel cell stack or the cell voltage has an upper limit value in the operating region, and a bidirectional high voltage DC-DC (DC-DC) converter (BHDC) is used to operate the fuel cell stack so as not to exceed the upper limit value.

[0004] Figure 1 FIG. 2 shows the distribution of the cell voltage in the fuel cell stop mode according to the related art. Figure 1 In the fuel cell stop mode (FC stop) in which the fuel cell power generation is stopped, the air supply is stopped to cause the oxygen partial pressure difference between the cells, and therefore, there is a significant deviation between the cell voltages. When the fuel cell stop mode is entered with a relatively low air flow rate and oxygen supply, the degree of oxygen unevenness between the cells increases, which further significantly increases the deviation between the cell voltages. In particular, some cells may be exposed to a high potential of catalyst degradation, thereby reducing the performance of the fuel cell stack.

[0005] The contents of the description provided as related art of the present invention are only for helping understanding of the background of the present invention and should not be considered as corresponding to the related art known to those of ordinary skill in the art. Summary of the invention

[0006] An object of the present invention is to provide a technology for reducing cell voltage variation in a fuel cell stop mode by resolving oxygen partial pressure differences between cells when entering a fuel cell stop mode in which power generation of a fuel cell is stopped.

[0007] According to an exemplary embodiment of the present invention, a control method for a fuel cell stop mode may include: measuring an air flow rate supplied to a fuel cell stack; when entering the fuel cell stop mode, determining an oxygen distribution state between cells included in the fuel cell stack based on the measured air flow rate; and adjusting the air supply based on the determined oxygen distribution state to supply air to the fuel cell stack, or interrupting the air supply to the fuel cell stack.

[0008] When measuring the air flow rate, a flow sensor configured to measure the air flow rate of a blower for supplying air to the fuel cell stack may be configured to measure the air flow rate. When determining the oxygen distribution state, the oxygen distribution state may be determined based on an air supply amount obtained by integrating the measured air flow rate over a predetermined integration time.

[0009] Additionally, when determining the oxygen distribution state, when the air supply amount is equal to or less than a predetermined reference air amount, it can be determined that the oxygen distribution is uneven. When determining the oxygen distribution state, the oxygen flow rate in the measured air flow rate can be estimated, and the oxygen distribution state can be determined based on the oxygen supply amount obtained by integrating the estimated oxygen flow rate within a predetermined integration time.

[0010] In addition, when determining the oxygen distribution state, when the oxygen supply amount is equal to or less than a predetermined reference oxygen amount, it can be determined that the oxygen distribution is uneven. When determining the oxygen distribution state, the oxygen consumption amount can be estimated based on the charge amount obtained by integrating the output current of the fuel cell stack within a predetermined integration time, and the oxygen distribution state can be determined based on the remaining oxygen amount obtained by subtracting the oxygen consumption amount from the oxygen supply amount.

[0011] When adjusting the air supply, in response to determining that the oxygen distribution is uneven, air can be supplied to the fuel cell stack, and in response to determining that the oxygen distribution is uniform, the air supply to the fuel cell stack can be interrupted. When determining the oxygen distribution state, the oxygen distribution state can be divided into multiple stages based on the degree of unevenness of the oxygen distribution. In adjusting the air supply, when the oxygen distribution is uneven, the additional supply of air supplied to the fuel cell stack can be reduced. Additionally, when adjusting the air supply, a blower configured to supply air to the fuel cell stack can be driven at a predetermined speed, and when the oxygen distribution becomes uneven (e.g., inconsistent), the drive time of the blower can be increased.

[0012] According to another exemplary embodiment of the present invention, a control system for a fuel cell stop mode may include: a state determination processor configured to determine an oxygen distribution state between cells included in a fuel cell stack based on an air flow rate supplied to the fuel cell stack; and an air supply controller configured to adjust the air supply to supply air to the fuel cell stack or interrupt the air supply to the fuel cell stack based on the oxygen distribution state determined by the state determination processor when entering the fuel cell stop mode.

[0013] The control system may further include: a flow sensor configured to measure an air flow rate of a blower configured to supply air to the fuel cell stack. The state determination processor may be configured to determine that the oxygen distribution is uneven when the air supply amount is equal to or less than a predetermined reference air amount based on an air supply amount obtained by integrating the measured air flow rate. In response to determining that the oxygen distribution is uneven, the air supply controller may be configured to adjust the air supplied to the fuel cell stack by driving the blower configured to supply air to the fuel cell stack.

[0014] The state determination processor may be configured to divide the oxygen distribution state into a plurality of stages based on the degree of uneven distribution of oxygen, and the air supply controller may be configured to reduce the additional supply amount of air supplied to the fuel cell stack when the oxygen distribution is uneven. The air supply controller may be configured to drive a blower configured to supply air to the fuel cell stack at a predetermined rotation speed, and increase the driving time of the blower when the oxygen distribution is uneven. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present invention will be more clearly understood through the following detailed description in conjunction with the accompanying drawings, in which:

[0016] Figure 1 shows the distribution of the cell voltage in the fuel cell stop mode according to the related art;

[0017] Figure 2 is a flow chart of a control method for a fuel cell stop mode according to an exemplary embodiment of the present invention;

[0018] Figure 3 is a flow chart of a control method for a fuel cell stop mode according to another exemplary embodiment of the present invention;

[0019] Figure 4 is a configuration diagram of a control system for a fuel cell stop mode according to an exemplary embodiment of the present invention; and

[0020] Figure 5 The distribution of the cell voltage in the fuel cell stop mode when the fuel cell stop mode is controlled according to an exemplary embodiment of the present invention is shown. DETAILED DESCRIPTION

[0021] It is understood that the term "vehicle" or "vehicle-related" or other similar terms used herein generally include motor vehicles, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles; ships including various boats, vessels, aircraft, etc.; and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels from non-petroleum resources). As mentioned herein, a hybrid vehicle is a vehicle with two or more power sources, such as both a gasoline-powered vehicle and an electric vehicle.

[0022] Although the exemplary embodiments are described as using multiple units to perform the exemplary processes, it should be understood that the exemplary processes can also be performed by one or more modules. Additionally, it should be understood that the term controller / control unit refers to a hardware device including a memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more processes further described below.

[0023] In addition, the control logic of the present invention may be embodied as a non-transitory computer readable medium on a computer readable medium containing executable program instructions executed by a processor, a controller / control unit, 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, such as by a telematics server or a controller area network (CAN).

[0024] The terms used herein are only used to illustrate the purpose of specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "one", "a kind of" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that when used in this specification, the words "include" and / or "comprise" specify the presence of the features, integers, steps, operations, elements and / or components, but do not exclude the presence 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.

[0025] Unless otherwise specified or obvious from the context, as used herein, the word "about" should be understood to be within the normal tolerance range in the art, such as within 2 standard deviations of the mean. "About" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05% or 0.01% of the stated value. Unless otherwise clearly seen from the context, all numerical values ​​provided herein are modified by the word "about".

[0026] The specific structure or functional description of the exemplary embodiment of the present invention disclosed in the specification is only exemplified for the purpose of describing the exemplary embodiment of the present invention, and the exemplary embodiment of the present invention can be implemented in various forms and should not be considered to limit the exemplary embodiment of the present invention. The present invention can have various forms and modifications, so specific embodiments will be illustrated in the drawings and described in detail in the specification. However, the present invention is not intended to be specifically disclosed in form, and it should be understood that the present invention includes all changes, equivalents or substitutes included in the spirit and technical scope of the present invention.

[0027] It should be understood that although the first, second and other words can be used to describe various elements, these elements should not be limited to the words. These words are only used to distinguish an element from another element. For example, without departing from the scope of the present invention, the first element can be called the second element, and similarly, the second element can be called the first element. It is understood that when an element is referred to as "connected to" another element, it can be directly connected to another element, or there can be an intermediate element. On the contrary, when an element is referred to as "directly connected to" another element, there is no intermediate element. At the same time, other expressions such as "between...", "immediately adjacent to..." or "adjacent to..." and "directly adjacent to..." describing the relationship between components can be similarly explained.

[0028] When referring to a particular element being "connected to" or "electrically connected to" a second element, the first element may be directly connected or electrically connected to the second element, but it is understood that a third element may be interposed therebetween. On the other hand, when referring to a particular element being "directly connected to" or "directly electrically connected to" a second element, it is understood that there is no third element therebetween. Other expressions used to describe the relationship between constituent elements such as "between" and "directly between" or "adjacent" and "directly adjacent to" are interpreted in the same manner. The terms used in this application are used only to describe specific embodiments and are not intended to limit the present invention.

[0029] Unless defined differently, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. Those terms defined in commonly used dictionaries should be interpreted as having the same meaning as the contextual meaning in the relevant field. Unless explicitly defined in this application, these terms should not be interpreted as having an ideal or overly formal meaning.

[0030] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same constituent elements in the drawings are denoted by the same reference numerals, and repeated description of the same elements will be omitted.

[0031] In particular, the fuel cell stack receives hydrogen and air from the hydrogen supply system and the air supply system, respectively, and generates electricity through the chemical reactions therein. The fuel cell stack is connected to the motor and the high-voltage battery. The electricity generated in the fuel cell stack is supplied to the motor or the high-voltage battery through a bidirectional high-voltage DC / DC converter (BHDC). In general, the air flow rate supplied by the fuel cell stack is variable based on the required output or current. In the low current control area where the required output or current in the fuel cell stack is relatively low, the fuel cell stack is operated by low flow control that reduces the air flow rate supplied to the fuel cell stack so that it is not exposed to high voltage.

[0032] In addition, by operating the BHDC to adjust the voltage of the fuel cell stack, the voltage of the fuel cell stack or the voltage of the battery included in the fuel cell stack is prevented from exceeding a predetermined voltage. Therefore, the durability of the fuel cell stack can be ensured. Based on the required output of the fuel cell stack and the state of charge (SOC) of the high-voltage battery, the fuel cell enters the fuel cell (FC) stop mode. In the fuel cell stop mode, the fuel cell vehicle is in a running state or a start-up state, and the air supply to the fuel cell stack is interrupted to stop the fuel cell stack from generating electricity. In particular, when the charge amount of the high-voltage battery is equal to or greater than the predetermined charge amount and the required output of the fuel cell stack is equal to or less than the predetermined power, the fuel cell stop mode can be entered.

[0033] In the fuel cell stop mode, the air supply to the fuel cell stack may be interrupted, and thus, the oxygen distribution state between the cells is uneven, resulting in a cell voltage deviation due to the presence of oxygen partial pressure. In particular, when the flow rate of air supplied to the fuel cell stack before entering the fuel cell stop mode is low, such a cell voltage deviation is relatively large, causing some cells to be exposed to a high potential, thereby causing degradation.

[0034] Figure 2 1 is a flow chart of a control method for a fuel cell stop mode according to an exemplary embodiment of the present invention. The method described below may be executed by a controller having a processor and a memory. Figure 2According to an exemplary embodiment of the present invention, a control method for a fuel cell stop mode may include: measuring an air flow rate supplied to a fuel cell stack (S100); when entering the fuel cell stop mode (S400), determining an oxygen distribution state between cells included in the fuel cell stack based on the measured air flow rate (S500); and adjusting the air supply to supply air to the fuel cell stack or interrupting the air supply to the fuel cell stack (S600).

[0035] In the operation S100 of measuring the air flow rate, the air flow rate supplied to the fuel cell stack per unit time can be measured in real time. As the air flow rate, a target value of the air flow rate supplied to the fuel cell stack by operating the blower using the output or current required by the fuel cell stack can be used. Alternatively, the air flow rate can be estimated by the revolutions per minute (rpm) of the blower. In particular, in the operation S100 of measuring the air flow rate, the air flow rate can be measured by a flow sensor configured to measure the flow rate of the blower that supplies air to the fuel cell stack. Therefore, the air flow rate can be measured more accurately in real time.

[0036] When the fuel cell enters the fuel cell stop mode (S400), in operation S500 of determining the oxygen distribution state, the oxygen distribution state between the cells included in the fuel cell stack can be determined based on the measured air flow rate. As described below, the oxygen distribution state can be divided into a uniform state or a non-uniform state, or can be divided into multiple stages. When the fuel cell enters the fuel cell stop mode (S400), in operation S600, adjustment is usually made to immediately interrupt the air supply (S620). In other words, usually, when the fuel cell enters the fuel cell stop mode to stop its power generation, the air supply is immediately interrupted. However, in the present invention, the air supply can be adjusted based on the determined oxygen distribution state, so that air is additionally supplied to the fuel cell stack, or the air supply to the fuel cell stack can be immediately interrupted (S600).

[0037] Before entering the fuel cell stop mode, the oxygen distribution state is affected by the air supply state. In other words, if a minimum amount of air or oxygen is supplied to the fuel cell stack immediately before the fuel cell enters the fuel cell stop mode, the oxygen distribution state of the fuel cell stack is uneven. In particular, before entering the fuel cell stop mode, the fuel cell stack is in a low current region where the fuel cell stack requires a smaller current in many cases, and the oxygen distribution state of the fuel cell stack may be uneven due to the low flow control of supplying the minimum amount of air to the fuel cell stack.

[0038] Specifically, according to an exemplary embodiment, in operation S500 of determining the oxygen distribution state (S500), the oxygen distribution state can be determined based on the air supply amount (S300) obtained by integrating the measured air flow rate within a predetermined integration time. In particular, the predetermined integration time can be set to several seconds in consideration of the time for gas distribution into the fuel cell stack. If the integration time is too short, the amount of air supplied to the battery in the fuel cell stack may not be properly reflected. If the integration time is too long, the oxygen in the air supplied to the battery may react with hydrogen or discharge, which may reduce the correlation with the amount of oxygen remaining in the battery. Therefore, the integration time must be set appropriately.

[0039] In particular, when the air supply amount is equal to or less than a predetermined reference air amount, it can be determined that the oxygen distribution is uneven. Conversely, when the air supply amount exceeds the predetermined reference air amount, it can be determined that the oxygen distribution is uniform. In a state where the fuel cell stack is fully generating electricity, the reference air amount can be appropriately set in consideration of the air amount for a predetermined integration time.

[0040] According to another exemplary embodiment, in the operation of determining the oxygen distribution state (S500), the oxygen flow rate in the measured air flow rate may be estimated (S200), and the oxygen distribution state may be determined based on the oxygen supply amount (S300) obtained by integrating the estimated oxygen flow rate within a predetermined integration time. The oxygen flow rate may be estimated by multiplying the oxygen concentration by the air flow rate. For example, typically, the oxygen concentration may be estimated based on the assumption that the oxygen concentration in the air is typically about 21%. Alternatively, the oxygen concentration may be measured in real time, and the oxygen flow rate may be estimated using the measured oxygen concentration.

[0041] For example, if the air flow rate is about 100 [kg / h], the oxygen flow rate can be estimated to be about 21 [kg / h], and when the molecular weight of oxygen is about 32 [g / mol], the oxygen supply per hour can be about 656 [mol], and the oxygen supply per second can be about 0.18 [mol]. In particular, if the oxygen supply is equal to or less than a predetermined reference oxygen amount, it can be determined that the oxygen distribution is uneven. On the contrary, if the oxygen supply exceeds the predetermined reference oxygen amount, it can be determined that the oxygen distribution is uniform.

[0042] According to another exemplary embodiment, in the operation of determining the oxygen distribution state (S500), the oxygen consumption amount may be estimated based on the charge amount obtained by integrating the output current of the fuel cell stack within a predetermined integration time, and the oxygen distribution state may be determined based on the remaining oxygen amount obtained by subtracting the oxygen consumption amount from the oxygen supply amount. Therefore, the oxygen distribution state may be determined more accurately using the remaining oxygen amount in the fuel cell stack.

[0043] In other words, the remaining oxygen amount can be calculated by subtracting the oxygen consumption from the oxygen supply over a predetermined integration time. The oxygen consumption can be estimated using the fact that it is proportional to the charge obtained by integrating the output current of the fuel cell stack over a predetermined integration time. Specifically, based on the fact that 4 [mol] electrons are generated per 1 [mol] of oxygen molecules, that each 1 [C] of charge is equivalent to the charge carried by 6.25*10^18 electrons, and that each 1 [mol] of electrons is 6.023*10^23 electrons, the oxygen consumption consumed by the reaction can be estimated using the charge obtained by integrating the output current.

[0044] In the operation of adjusting the air supply (S600), in response to determining that the oxygen distribution is uneven, air can be supplied to the fuel cell stack, and in response to determining that the oxygen distribution is uniform, the air supply to the fuel cell stack can be interrupted (S620). When the fuel cell stop mode is entered, the air supply to the fuel cell stack is usually interrupted immediately. However, in response to determining that the oxygen distribution is uneven, the air supply can be adjusted so that the air supply to the fuel cell stack is interrupted after the air is additionally supplied to the fuel cell stack (S610). Therefore, since air can be additionally supplied when the oxygen distribution is uneven, the battery voltage deviation can be solved and the durability can be ensured.

[0045] Figure 3 is a flow chart of a control method for a fuel cell stop mode according to another exemplary embodiment of the present invention. Figure 3 In another exemplary embodiment, in the operation of determining the oxygen distribution state (S500'), the oxygen distribution state can be divided into a plurality of stages based on the degree of unevenness of the oxygen distribution state, and in the operation of adjusting the air supply (S600), the air supply can be adjusted so that when the oxygen distribution becomes uneven (for example, the distribution becomes inconsistent), the additional supply amount of air supplied to the fuel cell stack is reduced (S610).

[0046] Specifically, based on the air supply, oxygen supply or residual oxygen amount, the oxygen distribution state can be divided into a plurality of stages (S510, S520). In particular, in determining the oxygen distribution state based on the air supply, oxygen supply or residual oxygen amount, when the air supply, oxygen supply or residual oxygen amount decreases, it can be determined that the unevenness of the oxygen distribution is serious. Therefore, the air supply can be adjusted so that the additional supply of air supplied to the fuel cell stack is increased when the oxygen distribution becomes uneven.

[0047] When the air supply amount, the oxygen supply amount, or the remaining oxygen amount is equal to or less than the first reference value (α) (S510), it can be determined that the unevenness of the oxygen distribution is serious and a large amount of additional air supply can be supplied (S611). Additionally, when the air supply amount, the oxygen supply amount, or the remaining oxygen amount exceeds the first value (α) and is less than the second reference value (β) (S520), it can be determined that the unevenness of the oxygen distribution is minimal and a minimum additional air supply can be supplied (S612). When the air supply amount, the oxygen supply amount, or the remaining oxygen amount exceeds the second reference value (β) (S520), it can be determined that the oxygen distribution is uniform and air can not be additionally supplied and the air supply can be interrupted (S620).

[0048] In the operation (S600) of adjusting the air supply, a blower configured to supply air to the fuel cell stack may be driven at a predetermined speed, and here, as the oxygen distribution becomes uneven, the driving time of the blower may be increased. The blower may be operated to drive at a predetermined fixed speed, and the additional supply of air may be changed by changing the driving time of the blower. In other words, the driving time of the blower may vary based on the oxygen distribution state divided into a plurality of stages. The driving time of the blower may be increased so that as the oxygen distribution becomes uneven, the additional supply of air supplied to the fuel cell stack is increased.

[0049] If the air supply amount, oxygen supply amount or residual oxygen amount is less than or equal to the first reference value (α), the blower may be driven for x1 seconds (S611), and when the air supply amount, oxygen supply amount or residual oxygen amount exceeds the first reference value (α) and is equal to or less than the second reference value (β), the blower may be driven for x2 seconds (S612), wherein x2 seconds is shorter than x1 seconds. The blower may be operated by the controller described herein.

[0050] Figure 4 is a configuration diagram of a control system for a fuel cell stop mode according to an exemplary embodiment of the present invention. Figure 4 According to an exemplary embodiment of the present invention, a control system for a fuel cell stop mode may include: a state determination processor 20, configured to determine an oxygen distribution state between cells included in the fuel cell stack 10 based on an air flow rate supplied to the fuel cell stack 10; and an air supply controller 30, configured to adjust the air supply based on the oxygen distribution state determined by the state determination processor 20 to supply air to the fuel cell stack 10 or interrupt the air supply.

[0051] The state determination processor 20 or the air supply controller 30 may be a component included in a fuel cell vehicle controller (FCU) such as an electronic control unit (FCU), or may be a sub-controller of the FCU. The state determination processor 20 may be configured to determine the oxygen distribution state between cells included in the fuel cell stack 10. The air supply controller 30 configured to adjust the air supplied to the fuel cell stack 10 may be configured to adjust the revolutions per minute (rpm) of the blower 40 supplying the air based on the required output of the fuel cell stack 10.

[0052] The control system may further include a flow sensor 50 configured to measure the air flow of the blower 40 that supplies air to the fuel cell stack 10. The flow sensor 50 may be disposed at the blower 40 and may be configured to measure the air flow supplied to the fuel cell stack 10 by the blower 40 in real time. The state determination processor 20 may be configured to determine that the oxygen distribution is uneven if the air supply amount is equal to or less than a predetermined reference air amount based on an air supply amount obtained by integrating the measured air flow rate within a predetermined integration time. In response to determining that the oxygen distribution is uneven, the air supply controller 30 may be configured to operate the blower 40 that supplies air to the fuel cell stack 10 to supply air to the fuel cell stack.

[0053] The state determination processor 20 may be configured to divide the oxygen distribution state into a plurality of stages based on the degree of unevenness of the oxygen distribution, and the air supply controller 30 may be configured to reduce the amount of air supply supplied to the fuel cell stack 10 when the oxygen distribution becomes uneven. The air supply controller 30 may be configured to drive the blower 40 that supplies air to the fuel cell stack 10 at a predetermined rotation speed, and here, the driving time of the blower 40 may increase as the oxygen distribution becomes uneven.

[0054] Figure 5 2 shows the distribution of the battery voltage in the fuel cell stop mode according to the control of the fuel cell stop mode according to an exemplary embodiment of the present invention. Figure 5 ,and Figure 1 In contrast, when entering the fuel cell stop mode (FC stop) according to the present invention, air can be additionally supplied while delaying the fuel cell from entering the stop mode. Figure 1 Compared with the case where air is immediately interrupted instead of being additionally supplied, it can be seen that the cell voltage deviation is significantly improved in the present invention. In other words, according to the present invention, when the oxygen distribution between the cells included in the fuel cell stack is uneven, air can be additionally supplied to the fuel cell stack, and therefore, the cell voltage deviation can be reduced and the exposure of the cells to high potential can be reduced, thereby enhancing the durability of the fuel cell stack.

[0055] While the present invention has been described and illustrated with respect to the specific exemplary embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A control method for a fuel cell stop mode, comprising the following steps: measuring, by a controller, the flow rate of air supplied to the fuel cell stack; When entering the fuel cell stop mode, determining, by the controller, a state of oxygen distribution between cells included in the fuel cell stack based on the measured air flow rate; as well as Based on the determined oxygen distribution state, adjusting air supply by the controller to supply air to the fuel cell stack or interrupting the air supply to the fuel cell stack, In the step of determining the oxygen distribution state, the oxygen consumption is estimated based on the charge amount obtained by integrating the output current of the fuel cell stack within a predetermined integration time, and the oxygen distribution state is determined based on the remaining oxygen amount obtained by subtracting the oxygen consumption from the oxygen supply.

2. The control method according to claim 1, wherein: In the step of measuring the air flow rate, the flow rate sensor is configured to measure the air flow rate of an air blower that supplies air to the fuel cell stack.

3. The control method according to claim 1, wherein: In the step of determining the oxygen distribution state, the oxygen distribution state is determined based on an air supply amount obtained by integrating the measured air flow rate over a predetermined integration time.

4. The control method according to claim 3, wherein: In the step of determining the oxygen distribution state, when the air supply amount is equal to or less than a predetermined reference air amount, it is determined that the oxygen distribution is uneven.

5. The control method according to claim 1, wherein: In the step of determining the oxygen distribution state, an oxygen flow rate in the measured air flow rate is estimated, and the oxygen distribution state is determined based on the oxygen supply amount obtained by integrating the estimated oxygen flow rate over a predetermined integration time.

6. The control method according to claim 5, wherein: In the step of determining the oxygen distribution state, when the oxygen supply amount is equal to or less than a predetermined reference oxygen amount, it is determined that the oxygen distribution is uneven.

7. The control method according to claim 1, wherein: In the step of adjusting the air supply, in response to determining that the oxygen distribution is uneven, air is supplied to the fuel cell stack, and in response to determining that the oxygen distribution is uniform, the air supply to the fuel cell stack is interrupted.

8. The control method according to claim 1, wherein: In the step of determining the oxygen distribution state, the oxygen distribution state is divided into a plurality of stages based on a degree of unevenness of the oxygen distribution, and in the step of adjusting the air supply, when the oxygen distribution becomes uneven, an additional supply amount of air supplied to the fuel cell stack is reduced.

9. The control method according to claim 8, wherein: In the step of adjusting the air supply, an air blower configured to supply air to the fuel cell stack is operated at a predetermined rotation speed, and when the oxygen distribution becomes uneven, a driving time of the air blower is increased.

10. A control system for a fuel cell stop mode, comprising: a state determination processor configured to determine a state of oxygen distribution between cells included in the fuel cell stack based on an air flow rate supplied to the fuel cell stack; as well as an air supply controller configured to, when entering the fuel cell stop mode, adjust air supply to supply air to the fuel cell stack or interrupt air supply to the fuel cell stack based on the oxygen distribution state determined by the state determination processor, Wherein, the state determination processor is configured as follows: An oxygen consumption amount is estimated based on a charge amount obtained by integrating an output current of the fuel cell stack over a predetermined integration time, and an oxygen distribution state is determined based on a remaining oxygen amount obtained by subtracting the oxygen consumption amount from an oxygen supply amount.

11. The control system of claim 10, further comprising: A flow sensor is configured to measure an air flow of a blower configured to supply air to the fuel cell stack.

12. The control system of claim 10, wherein: The state determination processor is configured to determine that the oxygen distribution is uneven when the air supply amount is equal to or less than a predetermined reference air amount based on an air supply amount obtained by integrating the measured air flow rate.

13. The control system of claim 10, wherein: In response to determining that the oxygen distribution is uneven, the air supply controller is configured to adjust air supplied to the fuel cell stack by operating an air blower configured to supply air to the fuel cell stack.

14. The control system of claim 10, wherein: The state determination processor is configured to divide the oxygen distribution state into a plurality of stages based on a degree of unevenness of oxygen distribution, and the air supply controller is configured to reduce an additional supply amount of air supplied to the fuel cell stack when the oxygen distribution becomes uneven.

15. The control system of claim 14, wherein: The air supply controller is configured to operate an air blower configured to supply air to the fuel cell stack at a predetermined rotation speed, and increase a driving time of the air blower when oxygen distribution becomes uneven.

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