Diagnostic method for diagnosing a state of a fuel cell system

Abstract

The present invention relates to a diagnostic method (100) for diagnosing a state of a fuel cell system (200), the diagnostic method (100) comprising: - determining (101) a current amount of liquid water generated during operation of the fuel cell system (200), - calculating (103) a water load for a plurality of components of the fuel cell system (200) based on the amount of water generated, - assigning (105) a characteristic value to each of the water loads determined for the plurality of components, - comparing (107) the characteristic value with a diagnostic threshold value, and - outputting (109) a warning message if the characteristic value is greater than or equal to the diagnostic threshold value.

Description

[0001] Description

[0002] title

[0003] The presented invention relates to a diagnostic method for diagnosing a state of a fuel cell system, a fuel cell system and a program product according to the appended claims.

[0004] State of the art

[0005] Polymer electrolyte membrane (PEM) fuel cells convert hydrogen and oxygen into electrical energy while generating waste heat and water.

[0006] A PEM fuel cell consists of an anode-side flow field supplied with hydrogen, a cathode-side flow field supplied with air, and cooling sections through which coolant flows.

[0007] A polymer electrolyte membrane including a catalyst layer and a gas diffusion layer are placed between the anode and cathode flow fields. Several such individual fuel cells are stacked to form a fuel cell stack to maximize the electrical voltage generated.

[0008] Within this fuel cell stack are supply channels that supply the individual cells with hydrogen, air, and coolant, and transport the depleted, moist air, heated coolant, and depleted anode gas away. The supply channels are called distributors, while the removal channels are called collectors. In most cases, the depleted air at the cathode outlet is discharged into the atmosphere via an exhaust line. However, for the efficient operation of a fuel cell stack, the anode-side exhaust gas is frequently recirculated, thereby increasing hydrogen efficiency.

[0009] The product water produced on the cathode side reaches the anode side through diffusion processes and must be separated by a droplet separator before entering the fuel cell stack in order to avoid degradation processes within the cells.

[0010] The efficiency of a mist eliminator is typically less than 100%, so liquid water must be used for components located downstream of the mist eliminator, such as a recirculation fan, which is often used for active recirculation of the anode gas.

[0011] Due to the design of these components, only a certain amount of liquid water, i.e., a water load, is permissible. Otherwise, component damage and even failure may occur.

[0012] Disclosure of the invention

[0013] Within the scope of the invention presented, a diagnostic method for diagnosing the condition of a fuel cell system, a fuel cell system, and a program product are presented. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details described in connection with the diagnostic method according to the invention naturally also apply in connection with the fuel cell system according to the invention or the program product according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other. The invention presented serves, in particular, to detect and, if necessary, prevent a condition of a fuel cell system, in particular an impending failure of components of the fuel cell system.

[0014] Thus, according to a first aspect of the invention presented, a diagnostic method for diagnosing a state of a fuel cell system is presented

[0015] The presented diagnostic method comprises determining a current amount of liquid water generated during operation of the fuel cell system, calculating a respective water load for a plurality of components of the fuel cell system based on the amount of water generated, assigning a characteristic value to respective water loads determined for the plurality of components, comparing the characteristic value with a diagnostic threshold value and issuing a warning message in the event that the characteristic value is greater than or equal to the diagnostic threshold value.

[0016] The presented diagnostic method is based on the calculation of a water load, i.e., an input of liquid water into respective components of the fuel cell system, such as fuel cells, a fuel recirculation system or an air conveying system.

[0017] A characteristic value is determined based on the respective water loads, for example by assigning a characteristic value to a sum of the respective water loads using an allocation scheme, so that an integrated characteristic value is determined which describes a state of the fuel cell system based on all water loads.

[0018] Alternatively, the characteristic value can comprise a plurality of sub-characteristic values, each of which is determined based on a water load of an individual component, so that, for example, the sub-characteristic values ​​can be weighted differently in order to compare them with the diagnostic threshold value or a respective sub-diagnostic threshold value.

[0019] If the characteristic value is greater than or equal to the diagnostic threshold, a warning message is issued, which may, for example, include a request to the user to visit a workshop to have the fuel cell system checked or serviced. Accordingly, the presented diagnostic procedure prevents damage to a fuel cell system caused by a high water load.

[0020] Optionally, the warning message can include control commands for controlling the fuel cell system, which, for example, switch the fuel cell system to an emergency mode in which particularly little liquid water is produced.

[0021] It may be provided that the characteristic value is continuously determined and stored in a non-volatile memory.

[0022] By continuously determining the characteristic value, for example, at a regular, predetermined time interval and / or at a predetermined operating point of the fuel cell system, a change in the characteristic value over time can be determined and compared with a change diagnosis threshold value, so that, for example, if a gradient of a characteristic value curve is greater than or equal to the change diagnosis threshold value, a change warning message can be issued, which indicates, for example, a critical age of the fuel cell system.

[0023] It may further be provided that the water load is calculated using a statistical model that assigns a water load value to a respective operating state of the fuel cell system using a fixed mathematical relationship.

[0024] A statistical model can determine a characteristic value without additional information from, for example, sensors of the fuel cell system.

[0025] It can further be provided that the water load is calculated by means of a physical model which assigns a value of the water load to a respective operating state of the fuel cell system, wherein the physical model simulates a physical state of the fuel cell system based on at least one measurement parameter from the following list of measurement parameters: supplied electrical current, coolant temperature, operating pressure and ambient temperature.

[0026] By taking into account a measurement parameter that describes a current state of the fuel cell system and changes depending on the state of the fuel cell system, a particularly precise water load can be determined.

[0027] It can further be provided that the operating state is determined on the basis of at least one state parameter from the following list of state parameters: metered amount of hydrogen, requested power, provided power, delivered air quantity.

[0028] Since the water load changes particularly depending on the respective operating state, taking the current operating state into account when determining the water load requires a particularly precise determination of the water load.

[0029] It may further be provided that when calculating the respective water load for the plurality of components, an efficiency of a droplet separator of the fuel cell system is taken into account.

[0030] Since different droplet eliminators have different efficiencies, the efficiency of a particular droplet eliminator directly impacts the water load of the components of a fuel cell system located downstream of the droplet eliminator. Accordingly, the efficiency of the respective droplet eliminator can be included, for example, as a coefficient in the calculation of the characteristic value.

[0031] It can also be provided that if the warning message is not reset within a specified period of time, operation of the fuel cell system is blocked. To prevent damage to the fuel cell system due to excessive water load, operation of the fuel cell system can be blocked if there is no response to a warning message, e.g., if the warning message is reset by a technician or deleted from the error log.

[0032] It can further be provided that the plurality of components only comprises components that are arranged downstream of a droplet separator of the fuel cell system in the flow direction.

[0033] Since a water load is strongly determined by the efficiency of a respective droplet eliminator, the presented diagnostic method is particularly suitable for components that are arranged downstream of a droplet eliminator of the fuel cell system.

[0034] According to a second aspect, the presented invention relates to a fuel cell system for converting energy. The presented fuel cell system comprises a fuel cell stack and a computing unit, wherein the computing unit is configured to carry out a possible embodiment of the presented diagnostic method.

[0035] According to a third aspect, the presented invention relates to a program product. The presented program product comprises program code means that configure a computing unit to execute a possible embodiment of the presented diagnostic method when the program product is executed on the computing unit.

[0036] Advantages that are described in detail for the diagnostic method for diagnosing a condition of a fuel cell system according to the first aspect of the invention apply equally to the fuel cell system for converting energy according to the second aspect of the invention and the program product according to the third aspect of the invention. Further advantages, features, and details of the invention emerge from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0037] They show:

[0038] Figure 1 shows a possible design of the presented diagnostic procedure, Figure 2 shows a possible design of the presented fuel cell system.

[0039] Figure 1 shows a diagnostic method 100 for diagnosing a condition of a fuel cell system.

[0040] The diagnostic method 100 comprises a determination step 101 in which a current amount of liquid water occurring during operation of the fuel cell system is determined, a calculation step 103 in which a respective water load for a plurality of components of the fuel cell system is determined based on the amount of water occurring, an assignment step 105 in which a characteristic value is assigned to respective water loads determined for the plurality of components, a comparison step 107 in which the characteristic value is determined using a diagnostic threshold value and an output step 109 in which a warning message is output in the event that the characteristic value is greater than or equal to the diagnostic threshold value.

[0041] Optionally, in order to calculate the respective water load for the plurality of components of the fuel cell system, an efficiency 111 of a droplet separator is included in the calculation step 103, so that the water load is determined only on the basis of a part of the accumulating water quantity that is not separated by the droplet separator.

[0042] In order to assign the characteristic value to the respective water loads determined for the plurality of components in the assignment step 105, for example, a sum of the determined water loads can be calculated and a characteristic value can be assigned to the calculated sum by means of an assignment scheme.

[0043] Figure 2 shows a fuel cell system 200. The fuel cell system 200 comprises a fuel cell stack 201 and a

[0044] Computing unit 203.

[0045] The computing unit 203 is configured to execute the diagnostic method 100 according to Figure 1.

Claims

Claims 1 . Diagnostic method (100) for diagnosing a condition of a fuel cell system (200), the diagnostic method (100) comprising: Determining (101) a current amount of liquid water produced during operation of the fuel cell system (200), Calculating (103) a respective water load for a plurality of components of the fuel cell system (200) based on the amount of water generated, Assigning (105) a characteristic value to respective water loads determined for the plurality of components, Comparing (107) the characteristic value with a diagnostic threshold value, outputting (109) a warning message in the event that the characteristic value is greater than or equal to the diagnostic threshold value.

2. Diagnostic method (100) according to claim 1, characterized in that the characteristic value is continuously determined and stored in a non-volatile memory.

3. Diagnostic method (100) according to claim 1 or 2, characterized in that the water load is calculated by means of a statistical model which assigns a value of the water load to a respective operating state of the fuel cell system (200) by means of a fixed mathematical relationship.

4. Diagnostic method (100) according to claim 1 or 2, characterized in that that the water load is calculated by means of a physical model which assigns a value of the water load to a respective operating state of the fuel cell system (200), wherein the physical model simulates a physical state of the fuel cell system (200) based on at least one measurement parameter from the following list of measurement parameters: supplied electrical current, coolant temperature, operating pressure and ambient temperature.

5. Diagnostic method (100) according to claim 3 or 4, characterized in that the operating state is determined on the basis of at least one state parameter from the following list of state parameters: metered amount of hydrogen, requested power, provided power, delivered air quantity.

6. Diagnostic method (1009) according to one of the preceding claims, characterized in that an efficiency of a droplet separator of the fuel cell system is taken into account when calculating the respective water load for the plurality of components.

7. Diagnostic method (100) according to one of the preceding claims, characterized in that in the event that the warning message is not reset within a predetermined period of time, operation of the fuel cell system (200) is blocked.

8. Diagnostic method (100) according to one of the preceding claims, characterized in that the plurality of components comprises only components that are arranged downstream of a droplet separator of the fuel cell system (200) in the flow direction.

9. A fuel cell system (20) for converting energy, the fuel cell system (200) comprising: a fuel cell stack (201), - a computing unit (203), the computing unit (203) being configured to execute a diagnostic method (100) according to any one of claims 1 to 8.

10. Program product, wherein the program product comprises program code means which Configure the computing unit to execute a diagnostic method (100) according to one of claims 1 to 8 when the program product is executed on the computing unit.

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