Fuel cell system and method for controlling it

Abstract

Fuel cell system, comprising: a supply line (10) configured to supply hydrogen and air to a stack; a gas concentration sensor (20) configured to detect impurities in the hydrogen and air supplied to the supply line (10) and in the air; a supply valve (30) arranged in the supply line (10) for regulating the supply of hydrogen and air; an outlet line (40) configured to discharge hydrogen and air from the stack; an outlet valve (50) arranged in the outlet line (40) for regulating the discharge of hydrogen and air; a controller (60) configured for joint operation with the gas concentration sensor (20) for detecting ingress of impurities; and Outlet valves (50) arranged at the front and rear ends of the stack to remove contaminated fuel in response to the detection of intruding contaminants, wherein the controller (60) is further configured such that it: determines whether the stacking stress drops due to impurities in the hydrogen; the supply valve (30) and the outlet valves (50) are controlled so that hydrogen and air are discharged from the stack and hydrogen and air are supplied to the stack when it is detected that the stack tension is dropping due to impurities in the hydrogen; and executes a logic to repeatedly switch the fuel cell system on and off for predetermined times.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a fuel cell system and a method for controlling the same, and in particular to a fuel cell system for diagnosing whether impurities of the fuel cell reaction gas, such as hydrogen and air, have entered a fuel cell of a vehicle, and for restoring the performance of a fuel cell stack when the impurities have entered the fuel cell of the vehicle, and a method for controlling the same. BACKGROUND

[0002] A fuel cell is a system for generating electrical energy in which the energy of a chemical reaction between hydrogen (or hydrogen in a hydrocarbon-based material such as methanol, ethanol, or natural gas) and oxygen is converted into electrical energy. The fuel cell is an environmentally friendly energy source that can replace fossil fuels. It generates power in various applications through a stacked configuration, where cell units are stacked, and serves as a small and portable power supply due to its four to ten times higher energy density than a small lithium battery.

[0003] Fuel cells can be further classified according to the electrolyte used, such as phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, polymer electrolyte membrane fuel cells, alkaline fuel cells, and so on. These fuel cells operate on the same principle, but utilize different fuel types, operating temperatures, catalysts, electrolytes, and other factors. According to related technologies, impurities in the fuel cell reaction gas, such as hydrogen and air, can enter a vehicle's fuel cell system while the vehicle is in motion. In particular, the fuel cell's performance can be reduced due to these impurities.

[0004] Fuel cell systems are known from US 2003 / 0 157 383 A1, DE 10 2014 224 611 A1 and DE 10 2012 209 467 A1, comprising a supply line configured to supply hydrogen and air to a stack; a gas concentration sensor configured to detect impurities in the hydrogen and air supplied to the supply line and in the air; a supply valve arranged in the supply line for regulating the supply of hydrogen and air; an outlet line configured to discharge hydrogen and air from the stack; an outlet valve arranged in the outlet line for regulating the discharge of hydrogen and air; and a controller configured to operate in conjunction with the gas concentration sensor to detect ingress of impurities.and exhaust valves located at the front and rear ends of the stack to remove contaminated fuel in response to the detection of intruding contaminants. OVERVIEW

[0005] The purpose of the present disclosure is to provide a fuel cell system for diagnosing whether impurities in the fuel cell reaction gas, such as hydrogen and air, have entered a fuel cell of a vehicle, and for restoring the performance of a fuel cell stack when the impurities have entered the fuel cell of the vehicle, and a method for controlling the same.

[0006] The problem is solved by a fuel cell system with the features of claim 1 and a method for controlling a fuel cell system with the features of claim 6. Advantageous further developments are found in the dependent claims.

[0007] According to an embodiment of the present disclosure, a fuel cell system comprises: a supply line configured to supply hydrogen and air to a stack; a gas concentration sensor configured to detect impurities in the hydrogen and air supplied to the supply line; a supply valve arranged in the supply line that regulates the supply of hydrogen and air; an outlet line configured to discharge the hydrogen and air from the stack; an outlet valve arranged in the outlet line that regulates the discharge of the hydrogen and air; a controller operating in conjunction with the gas concentration sensor that detects intruded impurities; and outlet valves at the front and rear ends of the stack for removing the contaminated fuel in response to the detection of intruded impurities.The control system is further configured to determine whether the stack voltage is dropping due to impurities in the hydrogen; to control the supply valve and the exhaust valves to discharge hydrogen and air from the stack and to supply hydrogen and air to the stack when it is determined that the stack voltage is dropping due to impurities in the hydrogen; and to execute logic to repeatedly switch the fuel cell system on and off for predetermined periods.

[0008] The control system may, in particular, include: a memory configured to store driving conditions, including temperature, humidity, and pressure, during vehicle operation in order to determine whether the driving conditions are normal and to determine a degree of normality; and a diagnostic part configured to cooperate with a control part (e.g., in the memory) and to determine the driving conditions and a diagnosed resistance value in order to determine whether contaminants have entered and to determine the extent of the contamination.

[0009] The controller can be configured to restore the stack's performance after fuel removal. The fuel cell system can have a stack inlet check valve located between the supply line and the stack to block the entry of hydrogen or air into the stack. The supply line can include a hydrogen supply line and an air supply line. The gas concentration sensor can include a hydrogen gas concentration sensor configured to detect impurities in the hydrogen and an air gas concentration sensor configured to detect impurities in the air. Additionally, the supply valve can include a hydrogen supply valve configured to regulate the hydrogen supply and an air supply valve configured to regulate the air supply.The exhaust line may contain a hydrogen exhaust line configured to expel hydrogen and an air exhaust line configured to expel air, and the exhaust valve may contain a hydrogen exhaust valve configured to control the expulsion of hydrogen and an air exhaust valve configured to control the expulsion of air.

[0010] According to another embodiment of the present disclosure, a method for controlling a fuel cell system may include: measuring the stack voltage while the fuel cell vehicle is being driven after it has been filled with hydrogen; determining whether the stack voltage is lower than a reference voltage; determining whether the purity of the hydrogen is anomalous in order to establish a driving condition if the stack voltage is lower than the reference voltage; determining whether the driving condition is normal; venting, removing, and refilling the contaminated fuel if the driving condition is normal; determining whether the fuel cell vehicle needs to be driven again briefly; executing logic by repeatedly starting and stopping the fuel cell vehicle if it needs to be driven again briefly; and determining whether the stack power has been restored.and determine that the power returns to normal in order to terminate the logic when the power is restored.

[0011] The driving condition can include temperature, pressure, coolant condition, and humidity. If the stack voltage is higher than the reference voltage, the procedure can include a determination that the hydrogen purity is normal. If the driving condition is abnormal, the procedure can include a determination, based on the driving condition, that performance has deteriorated. If the fuel cell vehicle does not need to be driven again for a short time, the procedure can also include opening an air shut-off valve based on the fuel cell vehicle's start / stop cycle. If performance is not restored, the procedure can include repeating an additional recovery logic to perform an additional check. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other tasks, features and advantages of the present disclosure will become apparent from the following detailed description in conjunction with the accompanying drawings; they show: Fig. 1 a view of a fuel cell system according to an embodiment of the present disclosure; and Fig. 2 a flowchart of a method for controlling a fuel cell system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0013] It is understood that the term "vehicle" or "vehicle-related" or other similar terms used herein generally refer to motor vehicles, such as passenger cars, including sports utility vehicles (SUVs), buses, trucks, various commercial vehicles, personal watercraft including various boats and ships, aircraft, and the like, and also includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles (rechargeable from an electrical outlet), hydrogen-powered vehicles, and other vehicles powered by alternative fuels (e.g., fuels derived from resources other than petroleum). As used herein, a hybrid vehicle is a vehicle with two or more sources of propulsion, e.g., vehicles powered by both gasoline and electric motors.

[0014] Although the exemplary implementation is described as using multiple units to execute the exemplary process, it is understood that the exemplary processes can also be executed by one or more modules. Furthermore, it is understood that the term controller / control unit refers to a hardware device containing memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute these modules in order to perform one or more of the processes described later.

[0015] Furthermore, the control logic of the present invention can be implemented as non-volatile, computer-readable media on a computer-readable medium with executable program instructions that are executed by a processor, a controller / control unit, or the like. Examples of computer-readable media include, but are not limited to, ROMs, RAMs, (CD)-ROMs, compact discs (CD)-ROMs, magnetic tapes, floppy disks, USB flash drives, smart cards, and optical data storage devices. The computer-readable recording medium can also be distributed across networked computer systems, allowing the computer-readable medium to be stored and executed in a distributed manner, e.g., by a telematics server or a controller area network (CAN).

[0016] The terminology used herein is intended to describe only certain embodiments and is not meant to limit the invention. As used herein, the singular forms "one" and "the" are to include the plural forms unless the context clearly indicates otherwise. Furthermore, it is understood that the terms "has" and / or "having" as used in this description indicate the presence of specified features, integer quantities, steps, operations, elements, and / or components, but indicate the presence or addition of one or more other features, integer quantities, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integer quantities, steps, operations, elements, components, and / or groups thereof.As used herein, the phrase “and / or” includes all combinations of one or more of the listed positions.

[0017] Exemplary embodiments of the present disclosure are described in detail with reference to the accompanying drawings. A fuel cell system according to an exemplary embodiment of the present disclosure may include a supply line 10 configured to supply hydrogen and air to a stack, a gas concentration sensor 20 configured to detect impurities in the hydrogen and air, a supply valve 30 configured to regulate the supply of hydrogen and air, an outlet line 40 configured to discharge hydrogen and air, an outlet valve 50 configured to regulate the discharge, a controller 60 configured to detect ingress of impurities, and discharge valves through which the contaminated fuel can be removed or discharged if impurities have entered, as shown in Fig. 1 shown.

[0018] The supply line, which can be connected to the stack in the fuel cell system for supplying hydrogen and air, can include a hydrogen supply line 11 and an air supply line 12. Specifically, the hydrogen supply line 11 can be configured to supply hydrogen to the stack, and the air supply line 12 can be configured to supply air to the stack. The gas concentration sensor can be configured to detect or measure impurities in the hydrogen and air in the supply line 10.

[0019] The gas concentration sensor 20 can include a hydrogen gas concentration sensor 21, configured to detect impurities in the hydrogen that have entered the hydrogen supply line 11, and an air gas concentration sensor 22, configured to detect impurities in the air that have entered the air supply line 12. The supply valve can be located in the supply line 10 to regulate the supply of hydrogen and air. Furthermore, the supply valve 30 can include a hydrogen supply valve 31, configured to regulate the supply of hydrogen through the hydrogen supply line 11, and an air supply valve 32, configured to regulate the supply of air through the air supply line 12.

[0020] The outlet line can be configured to discharge hydrogen and air from the stack. In particular, the outlet line 40 can include a hydrogen outlet line 41 connected to the hydrogen supply line 11 for discharging the supplied hydrogen from the stack, and an air outlet line 42 connected to the air supply line 12 for discharging the supplied air from the stack. The outlet valve can be arranged in the outlet line 40 for regulating the discharge of hydrogen and air. Furthermore, the outlet valve can include a hydrogen outlet valve 51 connected to the hydrogen outlet line 41 for regulating the discharge of hydrogen, and an air outlet valve 52 connected to the air outlet line 42 for regulating the discharge of air.

[0021] Furthermore, the control unit 60 can be operated together with the gas concentration sensor 20 to detect ingress of contaminants. In particular, the control unit 60 can include a control section 61, configured to determine whether a driving condition is normal, and a diagnostic section 62, configured to determine whether contaminants have ingress. The control section 61 can be part of a memory configured to store driving conditions such as temperature, humidity, and pressure during vehicle operation in order to determine whether the driving condition is normal and the degree of normality.

[0022] The diagnostic unit 62 can be operated together with the control unit 61 and configured to determine the operating conditions and a diagnosed resistance value in order to determine whether contaminants have entered the fuel system. The control unit 61 can also be used to determine the extent of the ingress (e.g., the quantity of contaminants). The exhaust valves can be located at the front and rear ends of the fuel stack to remove the contaminated fuel in response to the detected ingress.

[0023] The control unit 61 can be configured to restore the stack's power after the fuel has been removed. Furthermore, according to one embodiment of the present disclosure, the fuel cell system can include a stack inlet check valve 80 arranged between the supply line 10 and the stack to block the entry of hydrogen or air into the stack. In particular, the stack inlet check valve 80 can include a hydrogen stack inlet check valve 81 configured to block or throttle the entry of hydrogen, and an air stack inlet check valve 82 configured to block or throttle the entry of air.

[0024] Furthermore, a method for controlling a fuel cell system according to an embodiment of the present disclosure may include: measuring the stack voltage (S10), comparing the stack voltage and a reference voltage (S20), confirming a driving condition (S30), determining whether the driving condition is normal (S40), venting, removing, and replenishing the contaminated fuel (S50), determining whether the vehicle should be driven again (S60), repeating the vehicle start / stop cycle (S70), determining whether the stack power has been restored (S80), and terminating a logic when the power reaches the normal state (S90), as described in Fig. 2 is shown.

[0025] In particular, the stack voltage can be measured while the fuel cell vehicle is in operation after hydrogen has been added. It can then be determined whether the stack voltage measured during operation after hydrogen refueling is lower than the reference voltage. Furthermore, the finding that the stack voltage is lower than the reference voltage can confirm that an abnormal hydrogen purity is the cause of the driving conditions. These conditions can include temperature, pressure, coolant condition, and humidity.

[0026] If the stack voltage is higher than the reference voltage, the procedure may include determining that the purity of the hydrogen is normal (S21) (e.g., the hydrogen contains no impurities). Then it can be determined whether the operating conditions are normal, and if so, the contaminated fuel can be drained, removed, and replenished.

[0027] Furthermore, if the driving conditions are anomalous, the procedure can include a determination, based on these conditions, that the performance has deteriorated (S41). It can also determine whether the fuel cell vehicle needs to be driven again for a short time. In response to the determination that the vehicle needs to be driven again, a logic can be executed by repeatedly starting and stopping the vehicle.

[0028] If the fuel cell vehicle does not need to be driven again for a short time (S60), the procedure can include opening an air shut-off valve based on the fuel cell vehicle's start-stop cycle (S61). It can be determined whether the stack's power has been restored, and if the power has returned to normal after determining that the stack's power has been restored, the logic can be terminated. If the power has not been restored, the procedure can also include repeating additional recovery logic and performing an additional check (S81).

[0029] As described above, in one embodiment of the present disclosure, impurities that have entered the vehicle can be detected by means of a sensor. Furthermore, based on the driving conditions or by means of the control unit 60, it can be determined whether a performance deviation occurs during the vehicle's operation within a predetermined time after the hydrogen has been filled into the vehicle. In response to the determination that the driving conditions are normal, the control unit can determine that impurities have entered the vehicle after refueling.

[0030] Furthermore, after confirmation of the ingress of contaminants, the contaminated fuel can be drained or removed and refilled; starting the vehicle on / off can be repeated if starting and stopping does not occur, thus eliminating the need for additional short-term driving; the air shut-off valve can be deactivated if starting and stopping occurs, thus eliminating the need for additional short-term driving.

[0031] The effects and embodiments of the present disclosure are described with reference to the tables below. The embodiments specify, in particular, the performance at the time when the injection of the reaction gas containing impurities stops and at the time when highly purified reaction gas is injected during a performance recovery test.

[0032] Table 1 shows a performance recovery trend after CO poisoning, with an evaluation result after poisoning with impurities in the range of a few ppm within one hour, and Table 2 shows a performance recovery trend after H₂S poisoning, with an evaluation result after poisoning with impurities in the range of a few ppm within one hour. Tables 1 and 2 show that performance improves with increasing concentration and time. Table 1 Condition A stack B stack C stack Performance up to initial performance after poisoning No recovery process 81% 76% 71% Driving / Reactivation 91% 86% 88% Start / Stop 30 times 96% 92% 97% Supply of air into the stack 99% 100% 100% Table 2 Condition A stack B stack C stack Performance up to initial performance after poisoning No recovery process 90% 80% 87% High initial levels 93% 86% 92% performance / reactivation Start / Stop 30 times 96% 90% 95% Supply of air into the stack 98% 95% 96% Water supply / Cleaning 100% 98% 99%

[0033] Tables 1 and 2 above show that when measuring stacking performance without a dedicated recovery process, the stacking performance can be measured at or above a predetermined level under normal temperature, humidity, and flow conditions. However, during drive / reactivation and high output / reactivation cycles, an idle situation and a high output situation can be repeatedly experienced under normal temperature, humidity, and throughput conditions, and thus a predetermined drive time may be required until the stacking performance is restored to a predetermined level.

[0034] In other words, the recovery rate after poisoning is relatively slow, so it can be difficult for the vehicle to achieve normal, humid / high-output driving early in the journey. The fuel cell system installed in the vehicle uses water generated during operation to humidify the fuel stack, and therefore, due to a lack of water, it can be difficult to reach normal performance and restore power by driving at high output early in the journey. In other words, if poisoning occurs with impurities at a given concentration or higher, it can be difficult to release power during initial driving due to limited output or similar factors, making driving / reactivation challenging.

[0035] However, if the vehicle is repeatedly started and stopped, so that voltage passes through it repeatedly, the recovery rate can increase with the number of potential cycles. This is a driving control condition that reveals a driving condition more easily, requires a relatively shorter recovery process, imposes fewer restrictions on driving under temperature / humidity conditions, and is easier to utilize in the vehicle compared to no recovery process or driving without (high output power) / reactivation. In other words, the power recovery effect of a repeated process through general driving, as opposed to driving without a recovery process at (high output power) / reactivation, can prove to be relatively significant with increasing poisoning due to an increase in contaminant concentration / exposure time.

[0036] Furthermore, it can be seen that when air is introduced into the stack to open a stack inlet and outlet at room temperature, the effect of power recovery occurs through desorption of impurities by the formation of a high potential at an electrode, and a power recovery effect also occurs through desorption of impurities via an oxidation reaction at an electrode. In the case of carbon monoxide, the power is 100% restored after air has been introduced into a stack reaction surface. It can also be seen that in the case of hydrogen sulfide, when water is added to a gas reaction surface in the stack or when the gas reaction surface is cleaned with water, the power is restored by a process such as repeatedly passing through a potential by start / stop repetition, air introduction, or the like., not 100%, but is restored 100% by supplying water.

[0037] Furthermore, a fuel cell system according to an embodiment of the present disclosure can include the supply line 10, which is configured to supply hydrogen and air to the stack; the gas concentration sensor 20, which is configured to detect impurities in the hydrogen and air introduced into the supply line 10; the supply valve 30 arranged in the supply line 10 for regulating the supplied hydrogen and air; the outlet line 40, which is configured to discharge the hydrogen and air from the stack; the outlet valve 50 in the outlet line 40 for regulating the discharge of hydrogen and air; the control unit 60, which is operated together with the gas concentration sensor 20 to determine the ingress of impurities; and the outlet valves, which are arranged at the front and rear ends of the stack.to remove the contaminated fuel in response to the detection of intruding contaminants.

[0038] As described above, according to the embodiment of the present disclosure, if a rapid deterioration in performance occurs due to the ingress of contaminants into the fuel cell system, a cause of the rapid deterioration in performance can be determined, and if normal operation is difficult to achieve due to damage to the main components of the stack caused by the ingress of contaminants, the performance of the stack can be restored to a normal level, thereby improving the marketability and stability of the vehicle. REFERENCE MARK OF EACH OF THE ELEMENTS IN THE FIGURES 10 Supply line 20 Gas concentration sensor 30 Supply valve 40 Outlet pipe 50 exhaust valve 60 Control

Claims

[1] Fuel cell system comprising: a supply line (10) configured to supply hydrogen and air to a stack; a gas concentration sensor (20) configured to detect impurities in the hydrogen and air supplied to the supply line (10) and in the air; a supply valve (30) arranged in the supply line (10) for regulating the supply of hydrogen and air; an outlet line (40) configured to discharge hydrogen and air from the stack; an outlet valve (50) arranged in the outlet line (40) for regulating the discharge of hydrogen and air; a controller (60) configured for joint operation with the gas concentration sensor (20) for detecting ingress of impurities; and Outlet valves (50) arranged at the front and rear ends of the stack to remove contaminated fuel in response to the detection of intruding contaminants, wherein the controller (60) is further configured such that it: determines whether the stacking stress drops due to impurities in the hydrogen; the supply valve (30) and the outlet valves (50) are controlled so that hydrogen and air are discharged from the stack and hydrogen and air are supplied to the stack when it is detected that the stack tension is dropping due to impurities in the hydrogen; and executes a logic to repeatedly switch the fuel cell system on and off for predetermined times. [2] Fuel cell system according to claim 1, wherein the control system (60) comprises: a control unit (61) configured to store driving conditions, including temperature, humidity, and pressure, during the operation of a vehicle in order to determine whether the driving conditions are normal and to determine a degree of normality; and a diagnostic part (62) configured to cooperate with the control part (61) and to determine the driving condition and a diagnosed resistance value in order to determine whether contaminants have entered and to determine the extent of the contamination. [3] Fuel cell system according to claim 2, wherein the control part (61) is configured to restore the power of the stack after the fuel has been removed. [4] Fuel cell system according to claim 1, further comprising: a stack inlet shut-off valve (80) arranged between the supply line (10) and the stack to prevent the introduction of hydrogen or air into the stack. [5] Fuel cell system according to claim 1, wherein: the supply line (10) includes: a hydrogen supply line configured for supplying hydrogen and an air supply line configured for supplying air; the gas concentration sensor (20) includes a hydrogen gas concentration sensor configured to detect impurities in the hydrogen and an air gas concentration sensor configured to detect impurities in the air, the supply valve (30) includes a hydrogen supply valve configured to regulate the supply of hydrogen, an air supply valve configured to regulate the supply of air, the outlet line (40) contains a hydrogen outlet line configured to discharge the hydrogen, and the outlet valve (50) includes a hydrogen outlet valve configured to control the discharge of hydrogen and an air outlet valve configured to control the discharge of air. [6] Method for controlling a fuel cell system, comprising: Measuring the stack voltage by the controller (60) during the journey of the fuel cell vehicle using a sensor after the fuel cell vehicle has been filled with hydrogen; Determine by the control (60) whether the stack voltage is lower than a reference voltage; Determine by the control (60) whether the purity of the hydrogen is anomalous in order to determine a driving condition when the stack voltage is lower than the reference voltage; Determine, via the control (60), whether the driving condition is normal; Draining, removing and refilling the contaminated fuel when driving conditions are normal; Determine by the control unit (60) whether the fuel cell vehicle needs to be driven again for a short time; Execution of logic by the controller (60) by repeating start on / off when the fuel cell vehicle needs to be driven again for a short time; Determine, via the control (60), whether the stack's performance has been restored; and Determine through the control (60) that the power reaches the normal state in order to terminate the logic when the power is restored. [7] Method for controlling a fuel cell system according to claim 6, wherein the driving condition includes temperature, pressure, coolant condition and humidity. [8] Method for controlling a fuel cell system according to claim 6, wherein when the stack voltage is higher than the reference voltage, the purity of the hydrogen is determined to be normal. [9] Method for controlling a fuel cell system according to claim 6, wherein, when the driving condition is anomalous, it is determined on the basis of the driving condition whether the performance has deteriorated. [10] Method for controlling a fuel cell system according to claim 6, wherein, when the fuel cell vehicle does not need to be driven for an additional short time, the method includes opening an air shut-off valve by the control unit (60) based on the start-off of the fuel cell vehicle. [11] Method for controlling a fuel cell system according to claim 6, wherein, if the power is not restored, the method includes the repetition of an additional restoration logic by the controller (60) to perform an additional check.

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