DEVICE AND METHOD FOR DETECTING A STATE OF A FUEL CELL SYSTEM

Abstract

Method for detecting a state of a fuel cell system, comprising: Calculating (S103), by a processor, a duty cycle and an average output current based on real-time driving data for a predetermined driving time interval during operation of a fuel cell vehicle; Obtaining (S105), by a processor, a reference current value from the calculated duty cycle and the calculated average output current; and Determining (S109), by a processor, a state of a fuel cell system by selecting (S107) a state graph corresponding to the obtained reference current value among a plurality of state graphs that can vary depending on each reference current value, wherein obtaining (S105) the reference current value refers to processing for obtaining (S105) a current value based on the calculated average current when the duty cycle is 1.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a method, a non-transitory computer-readable medium and a device for detecting a state of a fuel cell system and, in particular, to a method, a non-transitory computer-readable medium and a device for detecting a state of a fuel cell system from a driving profile in real time. Description of the state of the art

[0002] A fuel cell vehicle typically includes a fuel cell stack including a plurality of fuel cells, a fuel supply system that supplies hydrogen as a fuel to the fuel cell stack, an air supply system that supplies oxygen serving as an oxidizer required for an electrochemical reaction, and a water and heat management system that controls / regulates the temperature of the fuel cell stack.

[0003] The fuel supply system supplies compressed hydrogen in a hydrogen tank to a fuel electrode (anode) of the fuel cell stack by reducing the pressure of the hydrogen, and the air supply system supplies outside air, which is blown in by operating an air blower, via an air electrode (cathode) of the fuel cell stack.

[0004] When hydrogen is supplied to the fuel electrode of the fuel cell stack and oxygen is supplied to the air electrode, hydrogen ions are generated through a catalytic reaction. The hydrogen ions are transferred through an electrolyte membrane to an oxidation electrode or air electrode. The hydrogen ions, electrons, and oxygen undergo an electrochemical reaction at the oxidation electrode, generating electrical energy. More specifically, an electrochemical reaction of hydrogen occurs at the fuel electrode, and an electrochemical reaction of oxygen occurs at the air electrode. In this case, electricity and heat are generated due to the movement of electrons, and steam or water is produced by the electrochemical reaction of a combination of oxygen and hydrogen.

[0005] Additionally, most systems include an exhaust / exhaust device to remove / expel byproducts such as steam, water, and heat generated when the fuel cell stack generates electrical energy, as well as unreacted gases such as residual hydrogen and oxygen. Gases such as steam, hydrogen, and oxygen are vented to the atmosphere through an exhaust duct via the exhaust / exhaust device.

[0006] In theory, there are two main conditions that could contribute to fuel cell stack dryout. One is when the fuel cell vehicle is operating at high temperature and high power, and the other is during low power. Dryout at high temperature and high power is attributed to a breakdown of the heat balance in a fuel cell stack. Whereas dryout at low power is attributed to a failure in the supply of sufficient air, poor temperature control, and a reduction in water production due to applying low current and not driving a load.

[0007] Drying out of a fuel cell stack results in a reduction in the output of the fuel cell stack. Furthermore, it takes a long time to recover to normal output. Furthermore, if the dryout continues for a long period of time, the performance of the fuel cell stack may be reduced to the extent that it is impossible to recover, thus likely causing the fuel cell stack to break down. Therefore, a method is needed to detect the dryout of a fuel cell stack and to perform an operation to restore the performance of the fuel cell stack when the dryout is detected, so that the fuel cell stack can easily recover from the dryout.

[0008] Although there are conventional methods for detecting fuel cell stack dryout, such as current interruption (CI) and electrochemical impedance spectroscopy (EIS), these methods use a specific current band and are therefore difficult to use in real time while the vehicle is operating. Furthermore, these methods are difficult to apply to a vehicle because they require additional high-performance hardware, which would impose additional costs on the consumer.

[0009] The document US 2006 / 0 012 340 A1 discloses a method for determining the voltage conditions of a fuel cell vehicle comprising an engine as a driving power source of the vehicle, an engine control device for controlling the operation of the engine, a fuel cell to which a reaction gas is supplied for generating electric current through an electrochemical reaction, and a battery device.

[0010] The document US 2012 / 0 292 990 A1 discloses a method for controlling a fuel cell vehicle, comprising: by the use of a control device, in a case where the load amount is a predetermined value or less, implementing an extremely low current control for performing power generation at an extremely low current below a lower limit current of the fuel cell for normal operation, and at the time of implementing the extremely low current control, setting an upper and a lower limit value for a target output voltage of the converter in accordance with the extremely low current, and controlling the output voltage of the fuel cell to be in a range between the upper and lower limit values.

[0011] The document US 2008 / 0 152 973 A1 discloses a fuel cell comprising a fuel cell stack with a fuel cell unit to enable appropriate control of a humid condition before the power generation efficiency of the fuel cell is reduced.

[0012] The document US 2006 / 0 055 246 A1 discloses a method and a device for controlling and adjusting the switching states of switches connected to the electrical poles or outputs of a fuel cell.

[0013] The document US 2006 / 0 222 916 A1 discloses a method for determining the maximum power point voltage of a fuel cell.

[0014] The document US 2012 / 0 116 722 A1 discloses a method for detecting defects in an electrochemical device.

[0015] The foregoing is provided merely to facilitate understanding of the background of the present invention and is not intended to imply that the present invention lies within the scope of the prior art already known to one of ordinary skill in the art. SUMMARY OF THE INVENTION

[0016] Accordingly, the present invention has been made in consideration of the above problems encountered in the prior art, and the present invention is intended to provide a method, a non-transitory computer-readable medium, and an apparatus for detecting a state of a fuel cell stack in real time, which make it possible to detect an optimal operating state of the fuel cell stack.

[0017] This object is achieved by the method of claim 1, the non-transitory computer-readable medium of claim 11, and the apparatus of claim 16. Further preferred embodiments are subject of the subclaims.

[0018] Advantageously, it is possible to detect a state of a fuel cell system as a wet or dry state in real time and to obtain optimal operating conditions for the fuel cell system, such as a relative humidity, a required water amount, and / or a maximum power, according to the detected condition. Furthermore, it is possible to better understand a state of a fuel cell (SFC) of a fuel cell system from a state graph, predict a state of a fuel cell vehicle, and ensure stable driving performance based on the predicted state of the fuel cell vehicle. Finally, it is also possible to monitor a state of a fuel cell system according to driving conditions in real time and prevent a fuel cell vehicle from driving under prohibited conditions.Accordingly, the durability of the fuel cell vehicle can be improved as a result of the above system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings Fig. 1 is a flowchart illustrating a method for detecting a state of a fuel cell system according to an embodiment of the present invention; and Fig. 2 is a diagram illustrating an example of a state graph according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Reference will now be made in detail to the various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below, since the embodiments of the present invention can be variously modified in many different forms. While the disclosure is described in connection with embodiments, it is to be understood that the present description is not intended to limit the disclosure to those embodiments. On the contrary, the disclosure is intended to cover not only the embodiments, but also various alternatives, modifications, equivalents, and other embodiments that may be included within the spirit and scope of the disclosure as described by the appended claims.

[0021] It should be understood that although the terms "first," "second," etc., may be used herein to describe various elements, these elements are not limited by these terms. These terms are used merely to distinguish one element from another. For example, a first element discussed below could be referred to as a second element without departing from the teachings of the present invention. Similarly, the second element could also be referred to as the first element.

[0022] It is understood that when an element is referred to as being "coupled" or "connected" to another element, it may be directly coupled or connected to the other element, or there may be intervening elements. Conversely, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is understood that no intervening elements are present. Other expressions explaining the relationship between elements, such as "between," "directly between," "adjacent / next," or "directly adjacent / contiguous," should be interpreted in the same manner.

[0023] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further understood that the terms "comprise" and / or "comprising," when used in this specification, describe the presence of the specified features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more features, integers, steps, operations, elements, components, and / or groups thereof.

[0024] Unless otherwise defined, all terms used herein include technical and scientific terms and have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It is further understood that terms / terms, such as those defined in common dictionaries, should be interpreted to have a meaning consistent with their context in the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal sense, unless expressly defined as such herein.

[0025] Additionally, it is understood that the methods described below are executed by at least one controller. The term controller refers to a hardware device comprising a memory and a processor configured to perform one or more steps that should be interpreted as its algorithmic structure. The memory is configured to store algorithmic steps, and the processor is specifically configured to execute said algorithmic steps to perform one or more processes described further below.

[0026] Furthermore, the control logic of the present invention may be embodied as non-transitory computer-readable media on a computer-readable medium comprising executable program instructions executed by a processor, controller, or the like. Examples of computer-readable storage media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable recording medium may also be decentralized in network-coupled computer systems such that the computer-readable medium is stored and executed in a distributed manner, e.g., by a telematics server or a controller area network (CAN).

[0027] Each element and its shape may be shown schematically or exaggerated to facilitate understanding of the invention. Some elements intended for an actual product are not shown or omitted from the drawings or description. The drawings should be understood only as aiding understanding of the invention. Throughout the drawings, the same reference numerals will designate the same or similar parts.

[0028] Fig. 1 is a flowchart illustrating a method for detecting a state of a fuel cell system according to an embodiment of the present invention. The logic for implementing this detection may be executed by a control processing unit (CPU) (i.e., processor), and a plurality of state graphs may be stored in a storage device (e.g., a memory or a disk drive). The following processes may be performed by a device for detecting a state of a fuel cell system, which includes a control device and a storage device.

[0029] With reference to Fig. 1, the method for recognizing a state of a fuel cell system according to an embodiment of the present invention includes a step S101 in which real-time driving data for a preset driving time interval of a fuel cell vehicle is acquired, a step S103 in which a duty cycle and an average output current are calculated based on the acquired driving data, a step S105 in which a reference current value is obtained according to the calculated duty cycle and the calculated average output current, a step S107 in which a state graph corresponding to the acquired reference current value is selected from among a plurality of state graphs, and a step in which a current state of a fuel cell (SFC) of the fuel cell system (ie, at the present time) is recognized using the selected state graph.The processes in the method for detecting a state of a fuel cell system can be performed repeatedly.

[0030] Factors that can affect the condition of the fuel cell system include the operating temperature, air flow rate, average output current, minimum air flow rate, duty cycle, etc. Duty cycle is understood herein to be the ratio of the time during which current is output from a fuel cell stack relative to the total driving time while a fuel cell vehicle is operating. The average current corresponds to the rate of water generation in the fuel cell stack during the operating time of the fuel cell vehicle.The flow rate of air corresponds to an amount of air supplied to the fuel cell stack while the fuel cell vehicle is operating, and the minimum flow rate of air corresponds to an amount of air supplied to the fuel cell stack in an idle period.

[0031] By driving the fuel cell vehicle for a predetermined period of time (hereinafter referred to as "driving time"), driving data of the fuel cell vehicle can be obtained. That is, the driving data can be obtained by monitoring an output current of the fuel cell stack over this driving time or period of time. A duty cycle can then be calculated from the driving data. Specifically, the duty cycle can be obtained by calculating a ratio of a current output time, which corresponds to a period of time during which a current is output from the fuel cell stack, with respect to the predetermined driving time. An average output current can also be calculated from the driving data. The average output current can be calculated by dividing a total current output from the fuel cell stack for the predetermined driving time by the driving time.

[0032] Furthermore, in the embodiment of the present invention, a reference current value can be obtained from the calculated duty cycle and the calculated average output current. Specifically, the reference current value refers to a current value obtained when the duty cycle calculated from the average output current is 1. For example, when the calculated duty cycle is 0.6 and the calculated average output current is 54A, the reference current value is 90A, which is the same as the output current obtained when the duty cycle is 1.

[0033] In the embodiments of the present invention, the state graphs may be different for each reference current value. That is, the average output current and the duty cycle may vary depending on the reference current value. Since the average output current and the duty cycle vary, the maximum output current of the fuel cell stack, the relative humidity at an inlet or outlet of the fuel cell stack, and the amount of water generated by the fuel cell stack may vary accordingly. As such, the state graph may be a graph in which the duty cycle, the average output current, the maximum output current, and the relative humidity are mapped together. For example, the duty cycle may correspond to a water generation ratio of the fuel cell stack, and the average output current may correspond to the water generation rate.The amount of water produced by the fuel cell stack can then be obtained from the duty cycle and the average output current.

[0034] That is, it is possible to detect the state of a fuel cell system based on each element, such as average output current, duty cycle, maximum output current, and relative humidity, which are mapped to the state graph selected according to the reference current value. The state graph may also vary depending on the operating temperature of a fuel cell stack, i.e., the driving temperature of a fuel cell vehicle.

[0035] Accordingly, the detection method and the state graph will now be described with reference to Fig. 2 described in detail.

[0036] Fig. 2 shows a diagram illustrating an example of a state graph according to an embodiment of the present invention. Referring to Fig. 2, the elements that can be determined from the state graph are a relative humidity at an inlet or outlet of a fuel cell stack, a relative duty cycle, an average output current, a maximum output current, a water generation rate, etc.

[0037] From the state graph corresponding to a specific reference value, a relative humidity and a required amount of water can be determined according to a relative duty cycle and an average output current of a fuel cell vehicle. That is, the state of the fuel cell system can be recognized based on the maximum output current of the fuel cell stack and the relative humidity at the inlet or outlet of the fuel cell stack, which are mapped to the calculated average output current and relative duty cycle.

[0038] For example, if among the elements used to detect the state of the fuel cell system, the duty cycle is 0.2 and the average output current is 24A, the reference current value is 120A. A state graph corresponding to a reference current value of 120A is selected. Then, a point corresponding to a duty cycle of 0.2 and an average output current of 24A is set. The relative humidity value at the inlet or outlet of the fuel cell stack required for normal driving and the amount of water to be generated by the fuel cell stack can be obtained based on the water generation rate corresponding to the relative humidity of the fuel cell stack and the average output current and water generation ratio corresponding to the duty cycle, which are indicated by the set point.

[0039] The relative humidity value at an inlet or outlet of a fuel cell stack and the amount of water to be generated by the fuel cell stack for normal driving can also be set in advance and stored as data in the storage device. By comparing the stored data, that is, the relative humidity and amount of water for normal driving, with an actual relative humidity and an actual amount of water generated by the fuel cell stack at a current time, the state of the fuel cell system can be recognized. Furthermore, the state of the fuel cell system can also be recognized by comparing the output current required for normal driving and the maximum output current.

[0040] For the purpose of detecting the state of the fuel cell system, the state of the fuel cell system can be divided into a plurality of state segments according to the duty cycle and the average output current. The state of the fuel cell system is then divided into a plurality of preset critical values ​​that serve as reference values ​​that distinguish the state segments from each other. In the state graph, the state segments can be distinguished by the critical values ​​of the duty cycle and the average current, which are determined according to the current driving conditions of a fuel cell vehicle.

[0041] For example, when a fuel cell system is in low-humidity conditions (dry-out condition), the duty cycle and average output current are relatively low. Consequently, the amount of water generated by a fuel cell stack, the relative humidity at the inlet or outlet of the fuel cell stack, and the maximum output current measured in real time are all low. Accordingly, the point corresponding to the actual driving conditions is set in the lower left part of the state graph.

[0042] On the other hand, when the fuel cell system is in high humidity conditions (overflow condition), the duty cycle, average output current, and amount of water generated by the fuel cell stack are relatively high, but the output current required to power a fuel cell vehicle is relatively low.

[0043] Furthermore, in normal conditions, as the duty cycle and average output current increase, the maximum output current increases accordingly.

[0044] More specifically, the state of the fuel cell system can be classified into a plurality of state sections (i.e., first to third state sections (1), (2), and (3)) by a plurality of critical values ​​(i.e., first and second critical values ​​(5) and (6)) of the duty ratio and the average output current. When the maximum output current during the running of the fuel cell vehicle is equal to or less than a preset maximum reference output current value (i.e., an output current value (4) indicating the state section (2), which is a normal state section), and when the duty ratio and the average output current are within a range of the first state section (1) among the first to third state sections (1), (2), and (3), the state of the fuel cell system can be detected as a first abnormal state.

[0045] When the maximum output current is less than or equal to the preset maximum reference output current (4) and when the duty ratio and the average output current are within a range of the third state section (3) among the first to third state sections (1), (2) and (3), the state of the fuel cell system is detected as a second abnormal state.

[0046] Alternatively, when the maximum output current exceeds the preset maximum reference output current (4) and when the duty ratio and the average output current are within a range of the second state section (2) among the first to third state sections (1), (2) and (3), the state of the fuel cell system is recognized as a normal state.

[0047] In the exemplary embodiment, the first state section (1) and the second state section (2) are distinguished by the first critical value (5) and the second state section (2) and the third state section (3) are distinguished by the second critical value (6).

[0048] The first abnormal condition may be referred to as a low SFC condition, and the second abnormal condition may be referred to as a high SFC condition. The low SFC condition means that a fuel cell vehicle is driven under low-humidity, i.e., dry, conditions. Accordingly, the power of the fuel cell stack can (or should) be increased so that the amount of water generated by the fuel cell stack can be increased, thereby reducing dryness. The high SFC condition means that a fuel cell vehicle is driven under high-humidity conditions. Accordingly, the power of the fuel cell stack can (or should) be decreased so that the amount of water generated by the fuel cell stack can be decreased, thereby suppressing humidity.

Claims

[1] Method for detecting a state of a fuel cell system, comprising: Calculating (S103), by a processor, a duty cycle and an average output current based on real-time driving data for a predetermined driving time interval during operation of a fuel cell vehicle; Obtaining (S105), by a processor, a reference current value from the calculated duty cycle and the calculated average output current; and Determining (S109), by a processor, a state of a fuel cell system by selecting (S107) a state graph corresponding to the obtained reference current value among a plurality of state graphs that can vary depending on each reference current value, wherein obtaining (S105) the reference current value refers to processing for obtaining (S105) a current value based on the calculated average current when the duty cycle is 1. [2] The method according to claim 1, wherein the duty ratio is obtained by calculating (S103) a ratio of a current output time during which a current is output from a fuel cell stack with respect to the predetermined travel time. [3] The method of claim 1, wherein the average output current is calculated by dividing a total current output from a fuel cell stack for the predetermined driving time interval by a driving time. [4] The method according to claim 1, wherein the state graph is a graph in which the duty cycle, the average output current, a maximum output current of a fuel cell stack, and a relative humidity at an inlet or outlet of the fuel cell stack are mapped together. [5] The method of claim 1, wherein in the state graph, the duty cycle corresponds to a water generation ratio of a fuel cell stack and the average output current corresponds to a water generation rate, and wherein determining (S109) the state of the fuel cell system comprises determining an amount of water generated by the fuel cell stack at the calculated duty cycle and the calculated average output current. [6] The method of claim 1, wherein determining (S109) the state of the fuel cell system comprises recognizing the state of the fuel cell system based on a maximum output current of a fuel cell stack and a relative humidity at an inlet or outlet of the fuel cell stack, which are mapped to the calculated average output current and the calculated relative duty cycle in the state graph. [7] The method according to claim 6, wherein determining (S109) the state of the fuel cell system comprises dividing the state of the fuel cell system into a plurality of state sections according to the duty cycle and the average output current using a plurality of critical values ​​as reference values ​​to distinguish the state sections from each other, and determining (S109) to which state section among the plurality of state sections the state of the fuel cell system belongs. [8] The method of claim 6, wherein determining (S109) the state of the fuel cell system comprises: Dividing the state of the fuel cell system into a plurality of state sections using a plurality of critical values ​​of the duty cycle and the average output current; Detecting the state of the fuel cell system as a first abnormal state when the maximum output current is equal to or less than a predetermined maximum reference output current and when the duty cycle and the average output current are within a range of a first state section among the plurality of state sections; Detecting the state of the fuel cell system as a second abnormal state when the maximum output current is equal to or less than a predetermined maximum reference output current and when the duty cycle and the average output current are within a range of a third state section among the plurality of state sections; and Detecting the state of the fuel cell system as a normal state when the maximum output current exceeds the predetermined maximum reference output current and when the duty cycle and the average output current are within a range of a second state section among the plurality of state sections. [9] The method of claim 1, wherein the state graphs differ according to an operating temperature of a fuel cell stack. [10] The method of claim 8, wherein the first state portion and the second state portion are distinguished by a first critical value, the second state portion and the third state portion are distinguished by a second critical value, and the first critical value is less than the second critical value. [11] A non-transitory computer-readable medium comprising program instructions executed by a processor, the computer-readable medium comprising: Program instructions that calculate a duty cycle and an average output current based on real-time driving data for a given driving time interval during operation of a fuel cell vehicle; Program instructions that obtain a reference current value from the calculated duty cycle and the calculated average output current; and Program instructions that determine a state of a fuel cell system by selecting (S107) a state graph corresponding to the obtained reference current value among a plurality of state graphs that vary depending on each reference current value, wherein the acquired reference current value refers to processing for obtaining (S105) a current value based on the calculated average current when the duty ratio is 1. [12] The non-transitory computer-readable medium of claim 11, wherein the program instructions that determine the state of the fuel cell system comprise program instructions that detect the state of the fuel cell system based on a maximum output current of a fuel cell stack and a relative humidity at an inlet or outlet of the fuel cell stack, which are mapped to the calculated average output current and the calculated relative duty cycle in the state graph. [13] The non-transitory computer-readable medium according to claim 12, wherein the program instructions that determine the state of the fuel cell system include program instructions that divide the state of the fuel cell system into a plurality of state sections according to the duty ratio and the average output current using a plurality of critical values ​​as reference values ​​to distinguish the state sections from each other, and determine which state section the state of the fuel cell system belongs to among the plurality of state sections. [14] The non-transitory computer-readable medium of claim 12, wherein the program instructions that determine the state of the fuel cell system comprise: Program instructions that divide the state of the fuel cell system into a plurality of state sections using a plurality of critical values ​​of the duty cycle and the average output current; Program instructions that detect the state of the fuel cell system as a first abnormal state when the maximum output current is equal to or less than a predetermined maximum reference output current and when the duty cycle and the average output current are within a range of a first state section among the plurality of state sections; Program instructions that detect the state of the fuel cell system as a second abnormal state when the maximum output current is equal to or less than a predetermined maximum reference output current and when the duty cycle and the average output current are within a range of a third state section among the plurality of state sections; and Program instructions that recognize the state of the fuel cell system as a normal state when the maximum output current exceeds the predetermined maximum reference output current and when the duty cycle and the average output current are within a range of a second state section among the plurality of state sections. [15] The non-transitory computer-readable medium of claim 11, wherein the state graphs differ according to an operating temperature of a fuel cell stack. [16] Device comprising: a processor configured to execute one or more processes; and a memory configured to store a process of the one or more processes executable by the processor, the process, when executed, being operable to: to calculate a duty cycle and an average output current based on real-time driving data for a given driving time interval during operation of a fuel cell vehicle; to obtain a reference current value from the calculated duty cycle and the calculated average output current; and to determine a state of a fuel cell system by selecting (S107) a state graph corresponding to the obtained reference current value among a plurality of state graphs that vary depending on each reference current value, wherein obtaining (S105) the reference current value refers to processing for obtaining (S105) a current value based on the calculated average current when the duty cycle is 1.

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