Diagnostic method and diagnostic system for diagnosing fuel cell

Abstract

The invention relates to a diagnostic method (100) for diagnosing at least one fuel cell of a fuel cell system, said diagnostic method (100) comprising the following steps: providing (102) at least two different polarization models (1) for extracting a fuel cell diagnostic parameter set (3) from a polarization curve (2) of the at least one fuel cell, acquiring (104) at least one polarization curve (2) from at least one measurement of at least one fuel cell, applying (106) at least two of the different polarization models (1) previously acquired to the at least one polarization curve (2) of the at least one fuel cell, and extracting (108) a fuel cell diagnostic parameter set (3) from at least one polarization curve (2) of the at least one fuel cell for each applied polarization model (1).

Description

Technical Field

[0001] The invention relates to a diagnostic method and a diagnostic system for diagnosing at least one fuel cell of a fuel cell system, as well as a computer program product associated with the diagnostic method. Background Art

[0002] The polarization curve is a measurement result with which various properties of a fuel cell can be evaluated. The polarization curve is a function of the fuel cell design (catalyst, membrane, etc.), operating conditions (relative humidity, temperature, pressure, etc.) and the ageing of the fuel cell components. The measurement is carried out on a fuel cell test bench of the fuel cell system, usually at a constant temperature and under defined operating conditions.

[0003] In order to determine the diagnostic parameters of the fuel cell from the corresponding polarization curve, a polarization model is used in the prior art. This polarization model is applied to the polarization curve, thereby extracting the required diagnostic parameters from the polarization model. The extracted diagnostic parameters can be used to draw inferences about the fuel cell, such as inferences about its degree of degradation.

[0004] A problem with known diagnostic methods is that their results depend on the polarization model used. It may not be possible to extract all desired diagnostic parameters with the polarization model used. It may also be the case that the polarization model provides inaccurate diagnostic parameters. Summary of the invention

[0005] The object of the present invention is to at least partially eliminate the above-mentioned problems. In particular, the object of the present invention is to provide an improved diagnostic method for diagnosing fuel cells which provides results that are as reliable as possible.

[0006] The above object is achieved by a diagnostic method having the features of claim 1, a computer program product having the features of claim 11 and a diagnostic system having the features of claim 12. Further features and details of the invention are derived from the dependent claims, the description and the figures. Here, the features and details described with respect to the diagnostic method according to the invention are of course also applicable in connection with the diagnostic system according to the invention and the computer program product according to the invention, and vice versa, so that the disclosures of the individual inventive aspects can or should always be referred to one another.

[0007] According to the present invention, a diagnostic method for diagnosing at least one fuel cell of a fuel cell system is provided, wherein the diagnostic method comprises the following steps:

[0008] - providing at least two different polarization models for extracting a fuel cell diagnostic parameter set from a polarization curve of at least one fuel cell,

[0009] - obtaining at least one polarization curve from at least one measurement of at least one fuel cell,

[0010] - applying at least two of the aforementioned different polarization models to at least one polarization curve of said at least one fuel cell, and

[0011] - for each applied polarization model, extracting a fuel cell diagnostic parameter set from at least one polarization curve of the at least one fuel cell.

[0012] Therefore, the diagnostic method of the present invention uses at least two different polarization models. As mentioned above, these polarization models are used to extract fuel cell diagnostic parameter sets from the respective polarization curves of one or more fuel cells. This fuel cell diagnostic parameter set may also include polarization losses as fuel cell parameters. These losses may include, for example, losses caused by diaphragm permeability, activation losses caused by slow cathode reactions (reaction kinetics), losses caused by ohmic resistance (resistance of electrolytes, catalyst layers, gas diffusion layers, bipolar plates, interface contacts and terminal connections), and concentration losses (product transport at reaction sites, limited by fluid dynamics (convection and diffusion) at macro and micro levels). This polarization model may be represented, for example, by one or more mathematical relationships, in particular functions. The polarization model may be represented, for example, by a function of the cell voltage with respect to various input parameters, wherein the input parameters may be, for example, operating parameters, operating conditions, etc. Possible examples of polarization models include Chamberline-Kim and Larminie-Dicks polarization models.

[0013] Due to the application of different polarization models to one or more polarization curves of one or more fuel cells, not only can a fuel cell diagnostic parameter set be extracted and thus obtained, but also a fuel cell diagnostic parameter set can be obtained for each applied polarization model. These fuel cell diagnostic parameter sets constitute a diagnosis of the at least one fuel cell here, because they represent characteristic data that can reflect the state or condition of the fuel cell (such as the degree of degradation) through the fuel cell parameters they contain. Of course, other diagnostic steps can also be performed subsequently, such as an estimation of the degree of degradation. According to the present invention, since there are now at least two fuel cell diagnostic parameter sets for different polarization models, better diagnostic results can be obtained, because these results no longer rely on a single polarization model that may only provide an inaccurate diagnosis. In particular, by comparing the fuel cell diagnostic parameter sets with each other (which will be described in detail later), more accurate diagnostic results can be obtained.

[0014] The diagnostic method can in principle be used to diagnose one or more fuel cells, in particular one or more complete, in particular interconnected, fuel cell stacks or complete fuel cell systems. For this purpose, a corresponding polarization curve can be obtained for each fuel cell, each fuel cell stack or each fuel cell system.

[0015] The measurements for obtaining the polarization curve can be carried out in particular on a test bench for at least one fuel cell of the fuel cell system, preferably at a constant temperature and under defined operating conditions. When the diagnostic method is being carried out, the measurement results of the measurements may already be available, so that only the polarization curve needs to be obtained from them. However, the measurements can also be carried out during the diagnostic method, as will be explained in detail later.

[0016] The individual method steps of the method according to the invention do not need to be carried out in the order in which they are listed. Instead, the method steps can also be carried out in an order different from this or simultaneously. In particular, some or all method steps can also be repeated, in particular continuously. Thus, a fuel cell diagnostic parameter set can be continuously extracted and in particular output. This makes it possible to implement real-time monitoring of the diagnostic method, in particular in real-time measurements (in which case the polarization curves are continuously acquired and the polarization model is applied to them), as will be explained in detail later.

[0017] As mentioned above, as another step in the diagnostic method, it can be provided that at least one or all extracted fuel cell diagnostic parameter sets are output. As to which extracted fuel cell diagnostic parameters are output, it can be determined by optional selection, in particular by discarding certain fuel cell diagnostic parameters, which will be explained in detail below with examples.

[0018] It may be provided that the diagnostic method further comprises the following steps:

[0019] - specifying fuel cell parameters for a fuel cell diagnostic parameter set to be retrieved, and

[0020] - selecting at least two of the provided polarization models based on the specified fuel cell parameters in the fuel cell diagnostic parameter set to be extracted,

[0021] In particular, only the selected polarization model is applied to the at least one polarization curve. This ensures that only polarization models that are able to output predetermined fuel cell parameters are selected from the provided polarization models for application to the polarization curve. Polarization models are therefore not considered, which do not contain the defined and therefore required fuel cell parameters in the provided fuel cell diagnostic parameter set. For example, if a degradation estimate is required for at least one fuel cell, the fuel cell parameters required for this can be predefined. Polarization models that do not provide these parameters in their fuel cell diagnostic parameter set can then be discarded. This makes it possible to intelligently select polarization models from a large number of polarization models provided, for example, in a database, in order to save computing resources of a corresponding diagnostic system that performs the diagnostic method and to achieve a faster diagnosis.

[0022] It can be provided that the diagnostic method further comprises comparing the provided polarization model with available input data and applying the selected polarization model, in particular one that does not require any further input data in addition to the available input data, to the at least one polarization curve. The input data can be, for example: voltage and / or current of the fuel cell, operating conditions (e.g. pressure, temperature, relative humidity, etc.) and / or fuel cell data (e.g. Pt loading, membrane thickness, etc.). It can thus be ensured that only those polarization models that can be diagnosed based on the at least one polarization curve obtained are applied to the at least one polarization curve.

[0023] Furthermore, the goodness of fit of each polarization model to at least one polarization curve can be determined, and the extracted fuel cell diagnostic parameter sets with a goodness of fit below a predetermined minimum goodness of fit can be discarded. The minimum goodness of fit can be predetermined accordingly to improve the reliability of the fuel cell diagnostic parameter set. It can therefore be ensured that only sufficiently reliable fuel cell diagnostic parameter sets are used for subsequent processing, in particular for outputting and / or estimating the degree of degradation of at least one fuel cell.

[0024] Furthermore, it can be provided that the extracted fuel cell diagnostic parameter sets of different polarization models are compared with one another. Thus, the fuel cell diagnostic parameter sets can be cross-validated and the diagnostic results can be confirmed in the case of substantial correspondence. This also allows the reliability of the diagnostic method and its results to be increased.

[0025] In particular, it can be provided that, based on the comparison, a common fuel cell diagnostic parameter set is formed for at least one fuel cell. Thus, the fuel cell parameters considered to be most reliable can be selected from the individual fuel cell diagnostic parameter sets and combined to form a common fuel cell diagnostic parameter set. However, for example, a common value, such as an average value, a weighted average value, a median value, etc., can also be calculated for the corresponding fuel cell parameters in different fuel cell diagnostic parameter sets, wherein the common value then forms a common fuel cell diagnostic parameter set.

[0026] The extracted fuel cell diagnostic parameter set can also be subjected to a credibility check. Here, for example, it can be checked whether the fuel cell parameters in the fuel cell diagnostic parameter set contradict other fuel cell diagnostic parameter sets or exceed a predetermined value range. If it is inferred that the extracted fuel cell diagnostic parameter set is not credible, it can be discarded. This further improves the reliability of the diagnostic method.

[0027] The fuel cell parameters of the extracted fuel cell parameter set can also be compared with degradation parameters and / or defect parameters in a database. The database can, for example, contain historical diagnostic result values ​​and / or values ​​from one or more simulation models. The fuel cell parameters can thus be compared with a database of defect characteristics and / or degradation characteristics in order to estimate the fault condition, damage and / or degree of degradation of the at least one fuel cell. In principle, it is also advantageous to let the fuel cell parameters evolve on their own, for example first using the polarization curve of a first data set and then using the polarization curve of a second data set, and repeating the same process. Thus, the parameters here in particular evolve over time.

[0028] In particular, the degradation of the at least one fuel cell can be estimated based on the fuel cell parameters of the extracted fuel cell parameter set. Such use of the extracted fuel cell parameter set is particularly advantageous, since a plurality of extracted fuel cell parameter sets can be provided simultaneously and / or only those parameter sets which have not been previously discarded can be used. With a large amount of parameter information, a very accurate and reliable estimation of the degradation of the at least one fuel cell can be made.

[0029] The measurement of the at least one fuel cell can also be performed as a component of the diagnostic method. In particular, the measurement can be performed at least sometimes in parallel with the application step and / or the extraction step of the diagnostic method. Thus, the polarization curve can be continuously updated and applied based on the measurement to provide a real-time diagnostic method that can integrate the at least one fuel cell into the test bench.

[0030] In this case, the measurement of the at least one fuel cell can be actively influenced by at least one of the extracted fuel cell diagnostic parameter sets. In other words, a feedback to the measurement method is performed based on at least one of the extracted fuel cell diagnostic parameter sets. By changing the measurement parameters in the measurement method, in particular on a test bench for the at least one fuel cell, the diagnostic result can be influenced accordingly.

[0031] It can also be advantageously provided that the extracted fuel cell diagnostic parameter set of the at least one fuel cell is actively influenced by the goodness of fit of each polarization model. Thus, the fuel cell can be actively influenced by the extracted fuel cell diagnostic parameter set.

[0032] The subject of the invention is also a computer program product comprising instructions which, when the program is run on a computer, cause the computer to carry out the diagnostic method according to the invention.

[0033] The computer program product of the invention therefore brings about the same advantages as explained in detail with reference to the diagnostic method of the invention.

[0034] The computer program product can be the computer program itself or a product such as a computer readable data memory on which a computer program for executing the method of the invention can be stored. Within the scope of the invention, analog circuit boards and display devices (such as oscilloscopes) can also preferably serve as computer program products.

[0035] The subject matter of the invention is also a diagnostic system for diagnosing at least one fuel cell of a fuel cell system, wherein the diagnostic system has the following modules:

[0036] - providing means for providing at least two different polarization models for extracting a set of diagnostic parameters from a polarization curve of at least one fuel cell,

[0037] - an acquisition module for acquiring at least one polarization curve from at least one measurement of at least one fuel cell,

[0038] - an application module for applying at least two of the previously acquired different polarization models to at least one polarization curve of the at least one fuel cell, and

[0039] - An extraction module for extracting a set of fuel cell diagnostic parameters from at least one polarization curve of the at least one fuel cell for each applied polarization model.

[0040] The diagnostic system of the invention thus brings about the same advantages as explained in detail with reference to the diagnostic method of the invention.

[0041] In particular, the diagnostic system can be set up and designed to carry out the diagnostic method according to the invention.

[0042] The above modules of the diagnostic system can be implemented, for example, by separate computer program codes or jointly by a shared computer program code and / or by separate or shared functional units of a computer. The modules can also be integrated into a shared module. The diagnostic system can in particular include one or more computers or be composed of one or more computers, which can include the above modules.

[0043] The modules can also be set up to perform other steps of the above-mentioned diagnostic method. However, corresponding additional modules can also be provided for each individual step, and these modules can be distinguished by the respective names of the corresponding steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further advantages, features and details of the invention emerge from the following detailed description of exemplary embodiments with reference to the figures.

[0045] Here, Figure 1 A schematic diagram showing an embodiment of a diagnosis method 100 and a diagnosis system 200 of the present invention is shown. DETAILED DESCRIPTION

[0046] In a first method step, three different polarization models 1 are provided 102 , here purely as an example. These can be represented, for example, by one or more mutually different mathematical relationships (in particular functions). The provision 102 is performed by a provision module 202 of the diagnosis system 200 .

[0047] In the next method step, a polarization curve 2 is acquired 104 from the measurement (operation) of one or more fuel cells on a corresponding test bench of these fuel cells of the fuel cell system. For example, a fuel cell stack is used here as an example, which can be measured in advance or can also be measured during the diagnostic method 100. The polarization curve 2 obtained from the measurement characterizes various properties of the fuel cell stack. The acquisition 104 can be performed by an acquisition module 204 of the diagnostic system 200.

[0048] In a further method step, different polarization models 1 are applied 106 to the polarization curve of the fuel cell stack by means of an application module 206 of the diagnostic system 200. Subsequently, in a next method step, a fuel cell diagnostic parameter set 3 is extracted 108 from the polarization curve 2 of the fuel cell stack by means of an extraction module 208 for each applied polarization model 1.

[0049] This now results in three extracted fuel cell diagnostic parameter sets 3, each based on a different initially provided polarization model 1. These fuel cell diagnostic parameter sets 3 can now be directly output by diagnostic method 100 and diagnostic system 200 (not shown) and / or undergo further method steps.

[0050] Figure 1 It is shown by way of example how in the next method step the comparison 110 of the fuel cell diagnostic parameter sets 3 is carried out by means of the comparison module 210 . Figure 1 It is shown by way of example how, in a subsequent method step, a common fuel cell diagnostic parameter set 4 is formed 112 based on the aforementioned comparison by means of a formation module 212. Thus, a common fuel cell diagnostic parameter set 4 can be formed for all individual fuel cell diagnostic parameter sets 3, which gives fuel cell parameters that are as accurate as possible for characterizing the fuel cell stack. These fuel cell parameters can be output or used in a further method step (not shown) to estimate the degree of degradation of the fuel cell stack.

[0051] Additionally or alternatively, the diagnostic method 100 may include further method steps not shown here, such as specifying fuel cell parameters to be extracted, comparing with input data, determining goodness of fit, plausibility checks, etc., which have been described in detail above.

[0052] The above explanation of the embodiments describes the present invention only by way of example.

[0053] Reference numerals list

[0054] 100 Diagnostic Methods

[0055] 102 offers

[0056] 104 Get

[0057] 106 Applications

[0058] 108 Extract

[0059] 110 Comparison

[0060] 112 Formation

[0061] 200 Diagnostic System

[0062] 202 Provide Module

[0063] 204 Get module

[0064] 206 Application Modules

[0065] 208 Extraction Module

[0066] 210 Comparison module

[0067] 212 Forming Module

Claims

1. A diagnostic method (100) for diagnosing at least one fuel cell of a fuel cell system, wherein: The diagnostic method (100) comprises the following steps: - providing (102) at least two different polarization models (1) for extracting a fuel cell diagnostic parameter set (3) from a polarization curve (2) of at least one fuel cell, - acquiring (104) at least one polarization curve (2) from at least one measurement of at least one fuel cell, - applying (106) at least two of the previously obtained different polarization models (1) to at least one polarization curve (2) of the at least one fuel cell, and - for each applied polarization model (1), extracting (108) a fuel cell diagnostic parameter set (3) from at least one polarization curve (2) of the at least one fuel cell.

2. The diagnostic method (100) according to claim 1, characterized in that: The diagnostic method (100) further comprises the following steps: - specifying fuel cell parameters for the fuel cell diagnostic parameter set (3) to be extracted, and - selecting at least two of the provided polarization models (1) according to the specified fuel cell parameters in the set of fuel cell diagnostic parameters (3) to be extracted, Therein, the selected polarization model (1) is applied to the at least one polarization curve (2).

3. The diagnostic method (100) according to claim 1 or 2, characterized in that: The diagnostic method (100) further comprises comparing the provided polarization model (1) with available input data and applying a selected polarization model (1) that does not require any input data other than the available input data to the at least one polarization curve (2).

4. The diagnostic method (100) according to one of the preceding claims, characterized in that The goodness of fit of each polarization model (1) for the at least one polarization curve (2) is determined, and extracted fuel cell diagnostic parameter sets (3) below a predetermined minimum goodness of fit are discarded.

5. The diagnostic method (100) according to one of the preceding claims, characterized in that Extracted fuel cell diagnostic parameter sets (3) of different polarization models (1) are compared with one another.

6. The diagnostic method (100) according to claim 5, characterized in that: Based on the comparison, a common fuel cell diagnostic parameter set (4) is formed for the at least one fuel cell.

7. The diagnostic method (100) according to one of the preceding claims, characterized in that The extracted fuel cell parameter set (3) is subjected to a credibility check.

8. The diagnostic method (100) according to one of the preceding claims, characterized in that The fuel cell parameters in the extracted fuel cell parameter set (3) are compared with degradation parameters and / or defect parameters in the database.

9. The diagnostic method (100) according to one of the preceding claims, characterized in that Degradation of the at least one fuel cell is estimated based on the fuel cell parameters in the extracted fuel cell parameter set (3).

10. The diagnostic method (100) according to one of the preceding claims, characterized in that The measurement of the at least one fuel cell is performed as part of the diagnostic method (100). 11 . A computer program product comprising instructions which, when the program is run by a computer, cause the computer to carry out the diagnostic method according to claim 1 .

12. A diagnostic system (200) for diagnosing at least one fuel cell of a fuel cell system, wherein: The diagnostic system (200) is characterized by comprising the following modules: - providing a module (202) for providing at least two different polarization models (1) for extracting a set of diagnostic parameters (3) from a polarization curve (2) of a fuel cell, - an acquisition module (204) for acquiring at least one polarization curve (2) from at least one measurement of at least one fuel cell, - an application module (206) for applying at least two of the previously obtained different polarization models (1) to at least one polarization curve (2) of the at least one fuel cell, and An extraction module (208) for extracting a set of fuel cell diagnostic parameters (3) from at least one polarization curve (2) of the at least one fuel cell for each applied polarization model (1).

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