Humidifier leakage diagnosis system and method for fuel cell system

Abstract

The invention relates to a humidifier leak diagnostic system and method for a fuel cell system. A humidifier leak diagnostic system for a fuel cell system includes a fuel cell stack. The humidifier leak diagnostic system also includes an air supply system including at least one of an air compressor, a humidifier, an air shut-off valve, or an air pressure control valve. The humidifier leak diagnostic system additionally includes a controller configured to enter a humidifier leak diagnostic mode based on an inlet air pressure of the fuel cell stack. The controller is further configured to determine whether a humidifier leak has occurred based on an output power or an output voltage of the fuel cell stack generated by adjusting at least one of an opening degree of the air shut-off valve or an opening degree of the air pressure control valve in the humidifier leak diagnosis.

Description

Technical Field

[0001] The present invention relates to a humidifier leakage diagnosis system and method for a fuel cell system. Background Art

[0002] A fuel cell system is a power generation system configured to react high-purity hydrogen stored in a high-pressure tank with oxygen in the air to generate electricity. In order to generate electricity properly, it is necessary to adjust the state of the air introduced from the outside. To this end, an air filter configured to filter out impurities in the air can usually be provided.

[0003] In addition, the air supplied to the fuel cell system should be maintained at an appropriate humidity so that the fuel cell stack can generate the required electricity. To this end, a humidifier configured to adjust the humidity of the air can be provided at the air supply system of the fuel cell system.

[0004] A plurality of hollow fiber membranes are arranged inside the humidifier. When a part of the hollow fiber membrane is ruptured, a part of the air inhaled into the humidifier may not be introduced into the fuel cell stack when passing through the ruptured hollow fiber membrane, and thus may be discharged to the outside again.

[0005] In this case, the amount of air introduced into the fuel cell stack may be insufficient. Therefore, the required output of the fuel cell stack may not be satisfied. When air continuously leaks from the humidifier, the power generation performance of the fuel cell stack may continuously decrease due to an increase in the voltage deviation of the unit cells constituting the fuel cell stack.

[0006] In the conventional case, leakage diagnosis of the humidifier is usually not performed. For this reason, a defective state of the humidifier may be erroneously regarded as a failure of the fuel cell stack. In this case, there may be a problem of replacing a fuel cell stack in a normal state with a new fuel cell stack. Even though the fuel cell stack is replaced with a new fuel cell stack, the defective state of the humidifier still exists. Therefore, there is a problem that a defective output of the fuel cell stack continues to be generated.

[0007] The content described in this background art section is only intended to enhance the understanding of the general background art of the present invention. Therefore, the background art section should not be regarded as an admission or an implication in any form that this content constitutes the prior art known to those of ordinary skill in the art to which the present invention pertains. Summary of the Invention

[0008] The present invention has been made in view of the above problems. An object of the present invention is to provide a humidifier leakage diagnosis system and method for a fuel cell system that can determine whether there is a humidifier leakage in the fuel cell system.

[0009] According to one aspect of the present invention, a humidifier leakage diagnosis system for a fuel cell system is provided. The humidifier leakage diagnosis system includes a fuel cell stack. The humidifier leakage diagnosis system further includes an air supply system, the air supply system including at least one of an air compressor, a humidifier, an air shut-off valve or an air pressure control valve. The humidifier leakage diagnosis system further includes a controller configured to enter a humidifier leakage diagnosis mode based on the inlet air pressure of the fuel cell stack. The controller is further configured to determine whether a humidifier leakage has occurred based on the output power or output voltage of the fuel cell stack generated by adjusting at least one of the opening degree of the air shut-off valve or the opening degree of the air pressure control valve in the humidifier leakage diagnosis.

[0010] The controller may be configured to set a reference pressure for the humidifier leakage diagnosis based on at least one of the speed of the air compressor, the opening degree of the air shut-off valve or the opening degree of the air pressure control valve. The controller may be configured to enter the humidifier leakage diagnosis mode when the measured inlet air pressure of the fuel cell stack is lower than the reference pressure for the humidifier leakage diagnosis.

[0011] The controller may be configured to accumulate the number of times when the measured inlet air pressure of the fuel cell stack is lower than the reference pressure for the humidifier leakage diagnosis. The controller may be configured to diagnose that a humidifier leakage has occurred when the accumulated number of times is equal to or greater than a reference accumulated number of times.

[0012] The controller may be configured to perform an additional humidifier leakage diagnosis when the output voltage of the fuel cell stack remains lower than a reference output voltage for a reference time or longer when (i) the air shut-off valve is opened to a first opening degree and (ii) the air pressure control valve is opened to a second opening degree or closed.

[0013] The controller may be configured not to enter the humidifier leakage diagnosis mode within a predetermined time when the output voltage of the fuel cell stack is equal to or higher than the reference output voltage when (i) the air shut-off valve is opened to a first opening degree and (ii) the air pressure control valve is opened to a second opening degree or closed.

[0014] The controller may be configured to gradually open the air shut-off valve in the additional humidifier leakage diagnosis. The controller may be further configured to derive an average value of the deviation of the output voltage of the fuel cell stack generated when gradually opening the air shut-off valve. The controller may be configured to diagnose that a humidifier leakage has occurred when the average output deviation is less than a reference average value.

[0015] The controller may be configured to enter the humidifier leakage diagnosis mode by additionally considering at least one of the output of the fuel cell stack or the state of health (SoH) of the fuel cell stack.

[0016] The controller may be configured to set a reference pressure for humidifier leak diagnosis based on at least one of the speed of the air compressor, the opening degree of the air shut-off valve, or the opening degree of the air pressure control valve. The controller may be configured to enter a humidifier leak diagnosis mode when i) the inlet air pressure of the fuel cell stack is measured to be lower than the reference pressure for humidifier leak diagnosis and ii) the output of the fuel cell stack is equal to or lower than a reference output.

[0017] The controller may be configured to set a reference pressure for humidifier leak diagnosis based on at least one of the speed of the air compressor, the opening degree of the air shut-off valve, or the opening degree of the air pressure control valve. The controller may be configured to enter a humidifier leak diagnosis mode when i) the inlet air pressure of the fuel cell stack is measured to be lower than the reference pressure for humidifier leak diagnosis and ii) the SoH of the fuel cell stack is equal to or higher than a reference SoH.

[0018] The controller may be configured to, in response to determining that a humidifier leak has occurred, control the air shut-off valve to open fully; and determine the degree of the humidifier leak based on the output of the fuel cell stack generated in the fully open state of the air shut-off valve.

[0019] According to another aspect of the present invention, there is provided a method for diagnosing a humidifier leak in a fuel cell system. The method for diagnosing a humidifier leak includes measuring, by a controller, the inlet air pressure of a fuel cell stack. The method for diagnosing a humidifier leak further includes entering, by the controller, a humidifier leak diagnosis mode based on the inlet air pressure. The method for diagnosing a humidifier leak additionally includes determining, by the controller, whether a humidifier leak has occurred based on the output power or output voltage of the fuel cell stack generated when the controller adjusts at least one of the opening degree of the air shut-off valve or the opening degree of the air pressure control valve during diagnosing the humidifier leak.

[0020] Measuring the inlet air pressure of the fuel cell stack may include setting a reference pressure for humidifier leak diagnosis based on at least one of the speed of the air compressor, the opening degree of the air shut-off valve, or the opening degree of the air pressure control valve. Entering the humidifier leak diagnosis mode may include entering the humidifier leak diagnosis mode when the inlet air pressure of the fuel cell stack is measured to be lower than the reference pressure for humidifier leak diagnosis.

[0021] Determining whether a humidifier leak has occurred may include: when i) the air shut-off valve is opened to a first opening degree and ii) the air pressure control valve is opened to a second opening degree or closed, the controller performs additional humidifier leak diagnosis when the output voltage of the fuel cell stack remains lower than a reference output voltage for a reference time or longer.

[0022] Determining whether a humidifier leak has occurred may include: in another humidifier leak diagnosis, gradually opening an air shut-off valve; deriving an average value of the deviation of the output voltage of the fuel cell stack generated when gradually opening the air shut-off valve; and diagnosing that a humidifier leak has occurred when the average output deviation value is less than a reference average value.

[0023] The humidifier leak diagnosis method may further include: before measuring the inlet air pressure of the fuel cell stack, measuring at least one of the output of the fuel cell stack or the state of health (SoH) of the fuel cell stack by a controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other objects, features, and other advantages of the present invention should be more clearly understood from the following detailed description presented in conjunction with the accompanying drawings, in which:

[0025] Figure 1 is a configuration diagram of a humidifier leak diagnosis system for a fuel cell system according to an embodiment of the present invention;

[0026] Figure 2 is a graph illustrating the humidifier leak diagnosis of a fuel cell system according to an embodiment of the present invention; and

[0027] Figure 3 is a flowchart of a method for diagnosing a humidifier leak in a fuel cell system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same or similar elements are denoted by the same reference numerals, and redundant descriptions thereof are omitted in the following description.

[0029] In the following description, when a specific description of a well-known function or configuration may obscure the gist of the present invention, its detailed description is omitted. Embodiments of the present invention should be more clearly understood from the drawings. However, the present invention should not be limited by the drawings. It should be understood that all modified embodiments, equivalent embodiments, and alternative embodiments that do not depart from the spirit and technical scope of the present invention are included in the present invention.

[0030] It should be understood that although terms such as "first", "second", etc. may be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another.

[0031] Unless otherwise clearly used, singular expressions include plural meanings.

[0032] In the present invention, each of the phrases such as "A or B", "at least one of A and B", "at least one of A or B", "A, B or C", "at least one of A, B and C", "at least one of A, B or C", and "at least one of A, B or C, or a combination thereof" may include any one or all possible combinations of the items listed together in the respective one phrase.

[0033] In the present invention, terms such as "comprising", "including", etc. are intended to indicate the presence of features, numerical values, steps, operations, elements, components, or combinations thereof. These terms do not exclude the possibility of the presence of another feature, numerical value, step, operation, element, component, or any combination or any addition thereof.

[0034] The controller may include a communication device, a memory, and at least one processor. The communication device is configured to communicate with another controller or a sensor to control the functions to be performed thereby. The memory is configured to store an operating system, logical commands, input / output information, etc. The at least one processor is configured to perform discrimination, calculation, determination, etc. required to control the functions to be performed.

[0035] When a component, device, element, etc. of the present invention is described as having a purpose or performing an operation, function, etc., the component, device, or element should be considered herein as "configured to" meet the purpose or perform the operation or function.

[0036] Figure 1 is a configuration diagram of a humidifier leakage diagnosis system for a fuel cell system according to an embodiment of the present invention.

[0037] Reference Figure 1 , the fuel cell system may include an air supply system 20 configured to supply air to the cathode of the fuel cell stack 100. The fuel cell system may further include a hydrogen supply system 30 configured to supply hydrogen to the anode of the fuel cell stack 100.

[0038] The air supply system 20 may include at least one of an air compressor 210, a humidifier 400, an air shut-off valve 230, or an air pressure control valve 250, or any combination thereof. The hydrogen supply system 30 may include at least one of a hydrogen tank 370, a hydrogen supply valve 310, an ejector 350, or a hydrogen purification valve 330, or any combination thereof.

[0039] The controller 500 may determine whether to enter the humidifier leakage diagnosis mode based on the inlet air pressure of the fuel cell stack 100. To measure the inlet air pressure of the fuel cell stack 100, a pressure sensor configured to measure the pressure of the air introduced into the cathode may be provided at the cathode inlet of the fuel cell stack 100.

[0040] The inlet air pressure of the fuel cell stack 100 can be adjusted according to the speed of the air compressor 210, the opening degree of the air cut-off valve 230, and the opening degree of the air pressure control valve 250. Data mapping of the estimated value or experimental value of the inlet air pressure of the fuel cell stack 100 according to the speed of the air compressor 210, the opening degree of the air cut-off valve 230, and the opening degree of the air pressure control valve 250 can be stored in the controller 500.

[0041] When the actual value of the inlet air pressure of the fuel cell stack 100 is less than the estimated value or experimental value of the inlet air pressure of the fuel cell stack 100 stored in the controller 500, this can indicate a leak in the humidifier 400.

[0042] Therefore, when the actual value of the inlet air pressure of the fuel cell stack 100 is less than the estimated value or experimental value of the inlet air pressure of the fuel cell stack 100, the controller 500 can enter the humidifier leak diagnosis mode.

[0043] When the controller 500 enters the humidifier leak diagnosis mode, the controller 500 can adjust at least one of the opening degree of the air cut-off valve 230 and / or the opening degree of the air pressure control valve 250. Then, the controller 500 can determine whether there is a leak in the humidifier 400 based on the output voltage of the fuel cell stack 100 generated according to the opening degree adjustment.

[0044] Generally, when a humidifier leak occurs, the amount of air introduced into the fuel cell stack 100 decreases. In this case, correspondingly, it can be expected that the output power of the fuel cell stack 100 or the output voltage of the fuel cell stack 100 is lower than the expected value.

[0045] Therefore, in response to determining that the output power of the fuel cell stack 100 or the output voltage of the fuel cell stack 100 is lower than the output power of the fuel cell stack 100 or the output voltage of the fuel cell stack 100 estimated after adjusting at least one of the opening degree of the air cut-off valve 230 and / or the opening degree of the air pressure control valve 250 and adjusting the speed of the air compressor 210, the controller 500 can determine that a leak has occurred in the humidifier 400.

[0046] There are various embodiments in which it is determined whether a leak has occurred in the humidifier 400 based on the measurement of the output power of the fuel cell stack 100 or the output voltage of the fuel cell stack 100. Hereinafter, embodiments regarding the conditions for entering the humidifier leak diagnosis mode and the diagnosis of the leak of the humidifier 400 are described in more detail.

[0047] When the speed of the air compressor 210, the opening degree of the air shut-off valve 230, and the opening degree of the air pressure control valve 250 are determined, an estimated value or an experimental value of the air pressure at the cathode inlet of the fuel cell stack 100 can be obtained, and its data can be mapped and stored in the controller 500. Accordingly, such a value can be set as the reference pressure for humidifier leakage diagnosis, and thus, the reference pressure can be set as a condition for entering the humidifier leakage diagnosis mode.

[0048] For example, when the speed of the air compressor 210 is adjusted to 20,000 RPM, the opening degree of the air shut-off valve 230 is adjusted to 10°, and the opening degree of the air pressure control valve 250 is adjusted to 0°, the cathode inlet pressure of the fuel cell stack 100 can be approximately 20 kPa. Therefore, in the case where the speed of the air compressor 210 is adjusted to 20,000 RPM, the opening degree of the air shut-off valve 230 is adjusted to 10°, and the opening degree of the air pressure control valve 250 is adjusted to 0°, this pressure can be set as the reference pressure for humidifier leakage diagnosis.

[0049] When, in the case where the speed of the air compressor 210 is adjusted to 20,000 RPM, the opening degree of the air shut-off valve 230 is adjusted to 10°, and the opening degree of the air pressure control valve 250 is adjusted to 0°, the actual value of the cathode inlet pressure of the fuel cell stack 100 is lower than 20 kPa, this situation is a situation where leakage of the humidifier 400 is suspected. Therefore, it is possible to execute entering the humidifier leakage diagnosis mode.

[0050] The controller 500 can accumulate the number of times when the inlet air pressure of the fuel cell stack 100 is measured to be lower than the reference pressure for humidifier leakage diagnosis. When the controller 500 enters the humidifier leakage diagnosis mode, the controller 500 can identify the accumulated number of times when the inlet air pressure of the fuel cell stack 100 is measured to be lower than the reference pressure for humidifier leakage diagnosis. Then, when the identified accumulated number of times is equal to or greater than the reference accumulated number, the controller 500 can diagnose that leakage has occurred in the humidifier 400.

[0051] When the accumulated number of times when the inlet air pressure of the fuel cell stack 100 is measured to be lower than the reference pressure for humidifier leakage diagnosis is less than the reference accumulated number, the controller 500 can measure the output power or output voltage of the fuel cell stack 100, thereby diagnosing whether leakage has occurred in the humidifier 400.

[0052] In an embodiment, when performing a humidifier leakage diagnosis for the humidifier 400, the controller 500 may measure the output voltage of the fuel cell stack 100 after the air shut-off valve 230 is opened to a first opening degree and the air pressure control valve 250 is opened to a second opening degree or the air pressure control valve 250 is closed. The air pressure control valve 250 may be closed or slightly opened. The controller 500 may enhance the reaction sensitivity of the fuel cell stack 100 through the adjustment as described above, so as to more accurately diagnose the leakage of the humidifier 400.

[0053] In an embodiment, a data map of the output voltage of the fuel cell stack 100 estimated according to the opening degrees of the air shut-off valve 230 and the air pressure control valve 250 and the speed of the air compressor 210 may be stored in the controller 500. In response to determining that the actually measured output voltage of the fuel cell stack 100 is lower than the output voltage of the fuel cell stack 100 estimated through identification in the data map according to the opening degrees of the air shut-off valve 230 and the air pressure control valve 250 and the speed of the air compressor 210, the controller 500 may diagnose that a leakage has occurred in the humidifier 400.

[0054] More specifically, the output voltage of the fuel cell stack 100 that can be identified in the data map may be set as a reference output voltage. Accordingly, under the same conditions, when the output voltage of the fuel cell stack 100 remains lower than the reference output voltage for a reference time or longer, the controller 500 may diagnose that a leakage has occurred in the humidifier 400.

[0055] Figure 2 is a graph showing the humidifier leakage diagnosis of the fuel cell system according to an embodiment of the present invention. Refer to Figure 2 , the controller 500 may control the fuel cell stack 100 to be in a stop mode (Fc Stop) for humidifier leakage diagnosis (time point i). When the fuel cell stack 100 enters the stop mode, the driving of the air compressor 210 stops, and the air pressure control valve 250 and the air shut-off valve 230 are closed. After sufficient time has elapsed since the fuel cell stack 100 entered the stop mode, the output voltage of the fuel cell stack 100 drops to 0V. Subsequently, the controller 500 may enter the humidifier leakage diagnosis mode (time point ii).

[0056] When the controller 500 enters the humidifier leakage diagnosis mode, the controller 500 may control the air shut-off valve 230 to be opened to a first opening degree. The controller 500 may also control the air pressure control valve 250 to be opened to a second opening degree. The controller 500 may further control the speed of the air compressor 210.

[0057] The controller 500 may set a reference output voltage based on the opening degrees of the air cutoff valve 230 and the air pressure control valve 250 and the speed of the air compressor 210. Then, the controller 500 may monitor the output voltage generated by the fuel cell stack 100 over time.

[0058] When the humidifier 400 is in a normal state, the monitored output voltage may be close to or may exceed the reference output voltage, and thus may increase to the voltage limit. However, when the humidifier 400 is in an abnormal state due to the occurrence of a humidifier leak, the output voltage may not reach the reference output voltage.

[0059] For example, referring Figure 2 , abnormal state shows such a result, where although the increase in the output voltage is smooth due to the occurrence of a not serious humidifier leak, the increase in the output voltage stops at a value that does not reach the reference output voltage.

[0060] Abnormal state shows such a result, where the introduction of air into the fuel cell stack is delayed due to the occurrence of a humidifier leak, and thus, the voltage increase is also delayed.

[0061] Abnormal state shows such a result, where the amount of air introduced into the fuel cell stack is very insufficient due to a serious humidifier leak situation, and thus, a failure of the voltage increase occurs.

[0062] When an abnormal state where the output voltage of the fuel cell stack 100 is lower than the reference output voltage is detected at or after the reference time, the controller 500 may determine that a leak has occurred in the humidifier 400. Then, the controller 500 may end the humidifier leak diagnosis for the humidifier 400 (time point iii).

[0063] On the other hand, when the output voltage of the fuel cell stack 100 generated during the humidifier leak diagnosis for the humidifier 400 is equal to or higher than the reference output voltage, the controller 500 may not determine that there is a leak in the humidifier 400. In this case, due to various reasons unrelated to the humidifier 400, such as a failure of the pressure sensor, a failure of the air compressor 210, etc., the air pressure of the fuel cell stack 100 may be measured as insufficient.

[0064] Therefore, when the output voltage of the fuel cell stack 100 is equal to or higher than the reference output voltage, the controller 500 may determine that a reversible deterioration generation state of the removable fuel cell system has occurred. In this case, the controller 500 may be configured not to enter the humidifier leak diagnosis mode within a predetermined time.

[0065] In another example, the controller 500 can diagnose a leak in the humidifier 400 based on the output of the fuel cell stack 100. For example, the controller 500 can set different opening ranges of the air shut-off valve 230. According to each set opening range, the controller 500 can open the air shut-off valve 230 and measure the output of the fuel cell stack 100 generated within the set opening range.

[0066] The controller 500 can calculate the average value of the output deviations between adjacent opening ranges and can diagnose that a leak has occurred in the humidifier 400 when the calculated average value is less than a reference average value.

[0067] For example, the minimum opening of the air shut-off valve 230 can be 0°, the maximum opening of the air shut-off valve 230 can be 45°, and the controller 500 can divide the opening range into ranges of 0° to 10°, 10° to 25°, 25° to 30°, and 30° to 45°. The controller 500 can measure the output of the fuel cell stack 100 within all 4 ranges at the same time.

[0068] Thereafter, the controller 500 can measure the average value of the output deviations between adjacent opening ranges. For example, the controller 500 can measure the output deviation within the range of 0° to 10°, the output deviation within the range of 10° to 25°, the output deviation within the range of 25° to 30°, and the output deviation within the range of 30° to 45°. Then, the controller 500 can calculate the average value of the output deviations. When the calculated average value is less than the reference average value, the controller 500 can diagnose that a leak has occurred in the humidifier 400.

[0069] For example, when the output does not increase smoothly despite gradually opening the air shut-off valve, the controller 500 can determine that there is a leak in the humidifier 400.

[0070] In an embodiment, in addition to the inlet air pressure of the fuel cell stack 100, considering the output of the fuel cell stack 100 and the state of health (SoH) of the fuel cell stack 100, the controller 500 can enter the humidifier leak diagnosis mode. The most direct effect that occurs when a leak occurs in the humidifier 400 is that an output lower than the required output of the fuel cell stack 100 is continuously generated during the operation of the fuel cell stack 100.

[0071] Obviously, the reason why the output of the fuel cell stack 100 cannot reach the required output may be deterioration caused by degradation of the catalyst layer, overflow, etc. in the fuel cell stack 100. To determine whether the insufficient output of the fuel cell stack 100 is caused by the deterioration of the fuel cell stack 100, the SoH of the fuel cell stack 100 can be considered.

[0072] For example, the reference pressure for humidifier leakage diagnosis of the humidifier 400 can be set based on at least one of the speed of the air compressor 210, the opening degree of the air shut-off valve 230, or the opening degree of the air pressure control valve 250, or a combination thereof. When the inlet air pressure of the fuel cell stack 100 is measured to be lower than the reference pressure for humidifier leakage diagnosis and the output of the fuel cell stack 100 is equal to or lower than the reference output, the controller 500 can enter the humidifier leakage diagnosis mode for the humidifier 400.

[0073] In an embodiment, a data map of the output estimated based on the opening degree of the air shut-off valve 230, the opening degree of the air pressure control valve 250, and the speed of the air compressor 210 can be stored. Thus, the controller 500 can adjust the opening degree of the air shut-off valve 230, the opening degree of the air pressure control valve 250, and the speed of the air compressor 210 to track the required output of the fuel cell stack 100 according to the data map.

[0074] In an embodiment, the controller 500 can set the current required output of the fuel cell stack 100 as the reference output. When the actual output of the fuel cell stack 100 still does not meet the reference output within a predetermined number of times or a predetermined time even if the controller 500 adjusts the opening degree of the air shut-off valve 230, the opening degree of the air pressure control valve 250, and the speed of the air compressor 210 to track the reference output, the controller 500 can determine that the output of the fuel cell stack 100 is equal to or lower than the reference output.

[0075] In addition, when the inlet air pressure of the fuel cell stack 100 is measured to be lower than the reference pressure, the controller 500 can enter the humidifier leakage diagnosis mode.

[0076] In addition, the controller 500 can determine whether the controller 500 should enter the humidifier leakage diagnosis mode by measuring the SoH of the fuel cell stack 100. For example, the SoH of the fuel cell stack 100 can be represented by a numerical value from 0 to 100. In the state where the manufacturing of the fuel cell stack 100 is completed, the fuel cell stack 100 has an SoH of 100 and thus can exhibit 100% performance. This performance can be referred to as the birth of life (BoL).

[0077] When the fuel cell stack 100 exhibits 50 to 60% of the BoL due to its use and the degradation caused by its use, this performance can be referred to as the end of life (EoL) of the fuel cell stack 100. Here, the EoL refers to the situation where the fuel cell stack 100 should be replaced.

[0078] In some cases, the output degradation of the fuel cell stack 100 may not be caused by a leak in the humidifier 400, but may be caused by the degradation of the fuel cell stack 100 itself. Therefore, the controller 500 can measure the SoH of the fuel cell stack 100. When the SoH of the fuel cell stack 100 is equal to or higher than the reference SoH and the inlet air pressure of the fuel cell stack 100 is measured to be lower than the reference pressure, the controller 500 can enter the humidifier leak diagnosis mode.

[0079] The reference SoH can be a numerical value corresponding to the EoL of the fuel cell stack 100.

[0080] In an embodiment, once it is determined that a leak has occurred in the humidifier 400, the controller 500 can fully open the air shut-off valve 230. Then, the controller 500 can determine the degree of leakage of the humidifier 400.

[0081] For example, the controller 500 can determine the degree of leakage of the humidifier 400 by comparing the output generated in the fully open state of the air shut-off valve 230 with the data mapping of the output estimated based on the opening degree of the air shut-off valve 230, the opening degree of the air pressure control valve 250, and the speed of the air compressor 210.

[0082] In response to determining that a leak has occurred in the humidifier 400, the controller 500 can drive the air compressor 210 at a speed higher than the speed of the air compressor 210 included in the data mapping to track the required output of the fuel cell stack 100. The controller 500 can also generate an alarm to prompt the user to obtain inspection services for the humidifier 400.

[0083] Figure 3 is a flowchart of a humidifier leak diagnosis method for a fuel cell system according to an embodiment of the present invention.

[0084] Reference Figure 3 , in step S200, the controller 500 can measure the inlet air pressure of the fuel cell stack 100. In step S300, the controller 500 can enter the humidifier leak diagnosis mode for the humidifier 400 based on the measured air pressure, and can determine whether a leak has occurred in the humidifier 400 based on the output voltage of the fuel cell stack 100 or the output of the fuel cell stack 100 generated when the controller 500 adjusts at least one of the opening degree of the air shut-off valve 230 and / or the opening degree of the air pressure control valve 250 during the diagnosis of the leak of the humidifier 400.

[0085] When measuring the inlet air pressure of the fuel cell stack 100 by the controller 500 in step S200, the controller 500 may set a reference pressure for humidifier leakage diagnosis based on at least one of the speed of the air compressor 210, the opening degree of the air cut-off valve 230, or the opening degree of the air pressure control valve 250, or a combination thereof.

[0086] Thereafter, in step (S200), the controller 500 may measure the inlet air pressure of the fuel cell stack 100, and then in step S330, the controller 500 may determine whether the inlet air pressure of the fuel cell stack 100 is measured to be lower than the reference pressure for humidifier leakage diagnosis. Based on the determined result, in step S350, the controller 500 may enter the humidifier leakage diagnosis mode for the humidifier 400. In addition, the controller 500 may set a humidifier leakage flag.

[0087] When the inlet air pressure of the fuel cell stack is determined to be lower than the reference pressure for humidifier leakage diagnosis, in step S350, the controller 500 may enter the humidifier leakage diagnosis mode for the humidifier 400. In step S400, when the number of times the inlet air pressure of the fuel cell stack is determined to be lower than the reference pressure for humidifier leakage diagnosis accumulates to, for example, 7 times or more, in step S700, the controller 500 may determine that a leak has occurred.

[0088] On the other hand, when the inlet air pressure of the fuel cell stack returns to the reference pressure for humidifier leakage diagnosis or higher with the leakage flag set, the controller 500 may perform additional leak sensing.

[0089] When further determining whether a leak has occurred in the humidifier 400, in the power generation stop state of the fuel cell stack in step S420, in step S440, the controller 500 may control the fuel cell stack 100 to generate an output voltage by controlling the air cut-off valve 230 to open to a first opening degree while controlling the air pressure control valve 250 to open to a second opening degree. In step S500, when the generated output voltage of the fuel cell stack 100 remains lower than the reference output voltage for a reference time or longer, the controller 500 may determine that a leak has occurred in the humidifier 400. If not, in step S600, the controller 500 may stop leak sensing within a predetermined time.

[0090] In another embodiment, when further determining whether a leak has occurred in the humidifier 400, at step S520, the controller 500 may set the opening range of the air shut-off valve 230, may open the air shut-off valve 230 according to the set opening range, and may measure the output voltage of the fuel cell stack 100 generated in each opening range. At step S540, when it is determined that the average value of the output deviation between adjacent opening ranges is less than the reference average value, the controller 500 may diagnose that a leak has occurred in the humidifier 400.

[0091] At step S700, when it is diagnosed that a leak has occurred in the humidifier 400, an alarm may be generated to prompt the user to obtain replacement or repair services for the humidifier 400.

[0092] In an embodiment, the humidifier leak diagnosis method may further include measuring at least one of the output of the fuel cell stack 100 or the SoH of the fuel cell stack 100 by the controller 500 before measuring the inlet air pressure of the fuel cell stack 100 by the controller 500 at step S200.

[0093] The controller 500 may measure the output of the fuel cell stack 100 or the SoH of the fuel cell stack 100 at step S100 before measuring the inlet air pressure of the fuel cell stack 100 at step S200. When the output of the fuel cell stack 100 is equal to or higher than the reference output, the controller 500 may determine the current operating state of the fuel cell stack 100 as the normal operating state, and thus, may continue to perform power generation.

[0094] When the output of the fuel cell stack 100 is lower than the reference output, the controller 500 may immediately measure the inlet air pressure of the fuel cell stack 100 at step S200, or may immediately measure the SoH of the fuel cell stack 100 at step S150.

[0095] When the SoH of the fuel cell stack 100 is lower than the reference SoH, the controller 500 may determine that the output reduction of the fuel cell stack 100 is caused by the deterioration of the fuel cell stack 100, and may generate an alarm to prompt the user to obtain replacement or repair services for the humidifier 400.

[0096] When the SoH of the fuel cell stack 100 is equal to or higher than the reference SoH, the controller 500 may measure the inlet air pressure of the fuel cell stack 100 at step S200 to determine whether the controller 500 should enter the humidifier leak diagnosis mode for the humidifier 400.

[0097] It can be clearly seen from the above description that according to the humidifier leak diagnosis system and method for a fuel cell system according to an embodiment of the present invention, it is possible to determine whether there is a leak in the humidifier in the fuel cell system.

[0098] Although embodiments of the present invention have been disclosed for illustrative purposes, those of ordinary skill in the art should understand that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the invention defined by the appended claims and their equivalents.

Claims

1. A humidifier leakage diagnostic system for a fuel cell system, the humidifier leakage diagnostic system comprising: Fuel cell stack; an air supply system including at least one of an air compressor, a humidifier, an air shutoff valve, or an air pressure control valve; and The controller is configured as: entering a humidifier leak diagnostic mode based on the inlet air pressure of the fuel cell stack; Whether a humidifier leak has occurred is determined based on an output power or an output voltage of the fuel cell stack generated by adjusting at least one of an opening of the air shutoff valve or an opening of the air pressure control valve in the humidifier leak diagnosis.

2. The humidifier leakage diagnosis system for a fuel cell system according to claim 1, wherein: The controller is configured as follows: setting a reference pressure for humidifier leak diagnosis based on at least one of a speed of an air compressor, an opening of an air shutoff valve, or an opening of an air pressure control valve; When the inlet air pressure of the fuel cell stack is measured to be lower than a reference pressure for humidifier leak diagnosis, the humidifier leak diagnostic mode is entered.

3. The humidifier leakage diagnosis system for a fuel cell system according to claim 2, wherein: The controller is configured as follows: accumulating the number of times the inlet air pressure of the fuel cell stack is measured to be lower than a reference pressure for humidifier leak diagnosis; When the accumulated number of times is equal to or greater than a reference accumulated number of times, it is diagnosed that a humidifier leak has occurred.

4. The humidifier leakage diagnosis system for a fuel cell system according to claim 2, wherein: The controller is configured to perform additional humidifier leak diagnosis when the output voltage of the fuel cell stack remains below a reference output voltage for a reference time or longer when i) the air shut-off valve is opened to a first opening and ii) the air pressure control valve is opened to a second opening or closed.

5. The humidifier leakage diagnosis system for a fuel cell system according to claim 2, wherein: The controller is configured not to enter the humidifier leakage diagnosis mode within a predetermined time when the output voltage of the fuel cell stack is equal to or higher than the reference output voltage when i) the air shut-off valve is opened to a first opening and ii) the air pressure control valve is opened to a second opening or closed.

6. The humidifier leakage diagnosis system for a fuel cell system according to claim 4, wherein: The controller is configured as follows: In additional humidifier leak diagnosis, gradually open the air shutoff valve; deriving an average value of deviations in the output voltage of the fuel cell stack generated when the air shutoff valve is opened; When the average value of the deviation of the output voltage is smaller than the reference average value, it is diagnosed that a humidifier leak has occurred.

7. The humidifier leakage diagnostic system for a fuel cell system according to claim 1, wherein: The controller is configured to enter the humidifier leak diagnostic mode further based on at least one of an output of the fuel cell stack or a health state of the fuel cell stack.

8. The humidifier leakage diagnosis system for a fuel cell system according to claim 7, wherein: The controller is configured as follows: setting a reference pressure for humidifier leak diagnosis based on at least one of a speed of an air compressor, an opening of an air shutoff valve, or an opening of an air pressure control valve; The humidifier leak diagnostic mode is entered when i) the inlet air pressure of the fuel cell stack is measured to be below a reference pressure for humidifier leak diagnostics and ii) the output of the fuel cell stack is equal to or below the output produced by the reference.

9. The humidifier leakage diagnosis system for a fuel cell system according to claim 7, wherein: The controller is configured as follows: setting a reference pressure for humidifier leak diagnosis based on at least one of a speed of an air compressor, an opening of an air shutoff valve, or an opening of an air pressure control valve; The humidifier leak diagnostic mode is entered when i) the inlet air pressure of the fuel cell stack is measured to be lower than a reference pressure for humidifier leak diagnosis and ii) the health state of the fuel cell stack is equal to or higher than the reference health state.

10. The humidifier leakage diagnosis system for a fuel cell system according to claim 1, wherein: The controller is configured to: in response to determining that a humidifier leak has occurred, Control the air shut-off valve to open as far as possible; The degree of humidifier leakage is determined based on the output of the fuel cell stack produced in a state where the air shutoff valve is opened to the maximum extent.

11. A humidifier leakage diagnosis method for a fuel cell system, the humidifier leakage diagnosis method comprising: Measuring the inlet air pressure of the fuel cell stack through the controller; entering, by the controller, a humidifier leak diagnostic mode based on the inlet air pressure; Whether a humidifier leak has occurred is determined by the controller based on the output power or output voltage of the fuel cell stack generated when the controller adjusts at least one of the opening of the air shutoff valve or the opening of the air pressure control valve when diagnosing a humidifier leak.

12. The humidifier leakage diagnosis method for a fuel cell system according to claim 11, wherein: Measuring the inlet air pressure of the fuel cell stack includes: setting, by a controller, a reference pressure for humidifier leakage diagnosis based on at least one of a speed of an air compressor, an opening of an air shutoff valve, or an opening of an air pressure control valve; Entering the humidifier leakage diagnosis mode includes entering the humidifier leakage diagnosis mode when an inlet air pressure of the fuel cell stack is measured to be lower than a reference pressure for humidifier leakage diagnosis.

13. The humidifier leakage diagnosis method for a fuel cell system according to claim 12, wherein: Determining whether a humidifier leak has occurred includes performing additional humidifier leak diagnosis by a controller when the output voltage of the fuel cell stack remains below a reference output voltage for a reference time or longer when i) the air shut-off valve is opened to a first opening and ii) the air pressure control valve is opened to a second opening or closed.

14. The humidifier leakage diagnosis method for a fuel cell system according to claim 13, wherein: Determining whether a humidifier leak has occurred includes: gradually opening the air shutoff valve by the controller in another humidifier leak diagnosis, deriving, by the controller, an average value of deviations of the output voltage of the fuel cell stack generated when the air shutoff valve is opened; By the controller, when the average value of the deviation of the output voltage is smaller than the reference average value, it is diagnosed that the humidifier leakage has occurred.

15. The humidifier leakage diagnosis method for a fuel cell system according to claim 11, further comprising: At least one of an output of the fuel cell stack or a health status of the fuel cell stack is measured, by the controller, prior to measuring an inlet air pressure of the fuel cell stack.

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