AT527297B1 - Diagnostic procedure for detecting faults in a fuel cell stack - Google Patents

Abstract

The present invention relates to a diagnostic method for detecting faults in the operation of a fuel cell stack of a fuel cell system, comprising the following steps: - determining a plurality of regeneration times, wherein a regeneration time is determined for each regeneration cycle of the fuel cell stack, and wherein the regeneration times occur one after the other in time, - determining a regeneration time interval between each successive regeneration time, - comparing the regeneration time intervals with a reference and/or comparing a function of the regeneration time intervals with a reference function in order to detect faults in the operation of the fuel cell stack, and - outputting a fault signal based on the comparison result.

Description

Description

DIAGNOSTIC PROCEDURE FOR DETECTING FAULTS IN A FUEL CELL STACK

[0001] The present invention relates to a diagnostic method for detecting faults in a fuel cell stack of a fuel cell system, a computer program product for carrying out such a diagnostic method and a diagnostic device.

[0002] It is known in the prior art that fuel cell stacks can degrade over time. A distinction is made between reversible degradation and irreversible degradation. Reversible degradation can be reversed. There are various regeneration methods to reverse reversible degradation. Irreversible degradation, on the other hand, cannot be reversed. With the known fuel cell stacks, it is not easy to say which part of the degradation is reversible and which part of the degradation is irreversible, or which faults occur. Irreversible degradation accounts for some of the faults that can occur in a fuel cell stack. In addition, other faults in the fuel cell stack can also occur.

[0003] Against this background, an object of the present invention is to at least partially eliminate the disadvantages described above. In particular, the object of the present invention is to determine faults in a fuel cell stack.

[0004] The above object is achieved by a diagnostic method with the features of claim 1, a computer program product with the features of claim 10 and a diagnostic device with the features of claim 11. Further features and details of the invention emerge from the subclaims, the description and the drawings. Features and details that are described in connection with the diagnostic method according to the invention naturally also apply in connection with the computer program product according to the invention and the diagnostic device 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.

[0005] Accordingly, a diagnostic method for detecting malfunctions in the operation of a fuel cell stack of a fuel cell system is provided. The diagnostic method comprises the following steps:

[0006] - Determining a plurality of regeneration times, wherein a regeneration time is determined for each regeneration cycle of the fuel cell stack, and wherein the regeneration times occur one after the other,

[0007] - determining a regeneration time interval between successive regeneration times,

[0008] - comparing the regeneration time intervals with a reference and/or comparing a function of the regeneration time intervals with a reference function in order to detect disturbances in the operation of the fuel cell stack, and

[0009] - Outputting a fault signal based on the comparison result.

[0010] By comparing the regeneration time intervals with a reference and/or comparing a function of the regeneration time intervals with a reference function, it can be detected whether the regeneration time intervals change in such a way that this can only be explained by a fault. In this way, faults in the operation of the fuel cell stack can be detected.

[0011] A regeneration cycle represents a renewal of the fuel cell stack in order to reverse the reversible degradation of the fuel cell stack. The regeneration times can be determined as follows. A parameter, e.g. the power or the

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Voltage falls below an operating point-dependent limit value at a certain operating point. If, for example, the voltage has fallen below the limit value, then the fuel cell stack needs to be renewed. A regeneration time is determined for each fully completed renewal.

[0012] The regeneration time interval represents the time between two consecutive regeneration times. Furthermore, the regeneration time interval can be in the range from 1 day to 20 weeks, in the range from 1 week to 10 weeks, and in particular in the range from 4 weeks to 8 weeks. However, in particular in stationary operation, the regeneration interval can also be in the range of minutes.

[0013] The regeneration cycle, i.e. the renewal of the fuel cell stack, can be in the range of 1 minute to 200 minutes, in the range of 10 minutes to 150 minutes, and in particular in the range of 30 minutes to 90 minutes.

[0014] The expression "wherein a regeneration time is determined for each regeneration cycle of the fuel cell stack" can mean that the regeneration time is determined at any point in time of the regeneration cycle, e.g. at the beginning or at the end. The respective regeneration time is always determined at the same point in the respective regeneration cycle.

[0015] It is particularly advantageous to always determine the point in time when the reversible regeneration has been fully completed. If the regeneration cycle could not be completed due to, for example, a change in operating mode or a shift in operating point, no point in time should be determined because it cannot be determined with certainty which portion of the reversible degeneration could actually be eliminated and this then influences the time interval between two regenerations.

[0016] The reference can represent the regeneration time interval that is to be expected in the event of a reversible degradation of the fuel cell stack that is to be expected under normal circumstances. As previously discussed, the regeneration time interval is highly dependent on the operation of the fuel cell, in particular on the operating point and whether dynamic operation or stationary operation is present. A deviation of a certain regeneration time interval from the reference can therefore mean a disruption of the operation of the fuel cell stack.

[0017] The reference function can represent a target function which is to be expected in the event of a reversible degradation of the fuel cell stack which is to be expected under normal circumstances. The target function indicates the expected regeneration time intervals over time. A deviation of the function of the regeneration time intervals from the reference function can then mean a disruption in the operation of the fuel cell stack.

[0018] In the present application, a fuel cell system is understood to mean a system (e.g. SOFC: Solid Oxide Fuel Cell) which has fuel cells for generating electrical energy using a fuel, or a system (e.g. SOEC: Solid Oxide Electrolyzer Cell) which has electrolysis cells for generating a fuel using electrical energy. A fuel cell stack therefore has several fuel cells or several electrolysis cells.

[0019] The described diagnostic method may be particularly relevant for stationary applications and continuously operating fuel cell systems.

[0020] According to an embodiment of the diagnostic method, each regeneration time is determined by continuously monitoring a parameter of the fuel cell stack. In this case, a regeneration signal is triggered if a value of the parameter falls below or exceeds a target parameter value. Advantageously, triggering the regeneration signal ultimately leads to a regeneration time being able to be determined. The expression "continuously monitored" can mean that the parameter is checked continuously or that the parameter is checked at short intervals.

[0021] According to a further embodiment of the diagnostic method, the parameter

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a power of the fuel cell stack, a voltage of the fuel cell stack, a time period, a number of operating hours, an amount of fuel consumed or an amount of energy produced. All of these parameters are suitable for monitoring the fuel cell stack. However, other parameters can also be used. The time period can be the total operating time of the fuel cell stack.

[0022] According to a further embodiment of the diagnostic method, the respective regeneration signal triggers a regeneration cycle of the fuel cell stack. Each regeneration time is the respective end time of the regeneration cycle of the fuel cell stack, in particular the respective end time of the fully completed regeneration cycle of the fuel cell stack. Alternatively, the regeneration times could also be at the beginning of the regeneration cycle or another specific time of the regeneration cycle can be specified.

[0023] According to a further embodiment of the diagnostic method, an environmental parameter is taken into account when creating the target barometer value. Such an environmental parameter can be, for example, the ambient temperature, the air pressure or the air humidity. The environmental parameter can influence the function of the fuel cell stack. Therefore, the environmental parameter can also be taken into account when creating the target barometer value. Alternatively, several environmental parameters can also be taken into account simultaneously.

[0024] According to a further embodiment of the diagnostic method, the reference is created by previously determined regeneration time intervals. The fault signal is output if a regeneration time interval has a deviation from the reference that is above a limit value. The regeneration time interval that is compared with the reference can in particular be the most recently determined regeneration time interval. This makes it possible to detect short-term faults in the fuel cell stack in particular. The previously determined regeneration time intervals can, for example, have been measured. Alternatively, the previously determined regeneration time intervals could also have been calculated. In particular, an average value can be formed for the previously determined regeneration time intervals.

[0025] According to a further embodiment of the diagnostic method, the function of the regeneration time intervals is created as a temporal progression of the determined regeneration time intervals. In this case, a gradient of the function is calculated, with a fault signal being output if the calculated gradient is above or below a limit value. The gradient is a derivative of the function with respect to time. The gradient can also be determined only from one area of the function, e.g. in particular from an end area. This is particularly necessary if no uniform gradient can be determined over the entire course of the function. Using the calculated gradient, it can be recognized whether there is a disruption in the operation of the fuel cell stack.

[0026] According to a further embodiment of the diagnostic method, the function of the regeneration time intervals is extrapolated as a temporal progression of the determined regeneration time intervals in order to create a diagnosis for the future progression of the regeneration time intervals. For example, from a progression of the regeneration time intervals of first 6 hours, then 5 hours and then 4 hours, it can be concluded that the next regeneration time interval is less than or equal to 4 hours. The diagnosis can be used to make a prediction about the length of the future regeneration time intervals.

[0027] According to a further embodiment of the diagnostic method, an environmental parameter is taken into account when creating the reference or the reference function. The environmental parameter can be, for example, the ambient temperature, the air pressure or the humidity. The environmental parameter can influence the function of the fuel cell stack. Therefore, the environmental parameter can also be taken into account when creating the reference or the reference function. Alternatively, several environmental parameters can also be taken into account simultaneously.

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[0028] Furthermore, the present invention relates to a computer program product having instructions which, when executed by a computer, cause the computer to carry out the steps of a diagnostic method according to the invention. A computer program product according to the invention therefore also brings with it the same advantages as have been explained in detail with reference to a diagnostic method according to the invention.

[0029] Furthermore, a diagnostic device for detecting faults in the operation of a fuel cell stack of a fuel cell system is provided. The diagnostic device comprises a regeneration time point determination module for determining a plurality of regeneration times, wherein a regeneration time point can be determined in each regeneration cycle of the fuel cell stack, and wherein the regeneration time point determination module is set up to determine the regeneration times one after the other, a regeneration time interval determination module for determining a regeneration time interval between successive regeneration times, a comparison module for comparing the regeneration time intervals with a reference and/or comparing a function of the regeneration time intervals with a reference function in order to detect faults in the operation of the fuel cell stack, and an output module for outputting a fault signal based on the comparison result of the comparison module.

[0030] The regeneration time point determination module, the regeneration time interval determination module, the comparison module and the output module are designed in particular for carrying out a diagnostic method according to the invention.

[0031] Because the comparison module can compare the regeneration time intervals with a reference and/or the function of the regeneration time intervals with a reference function, it is possible to draw conclusions about malfunctions in the operation of the fuel cell stack. The reference or the reference function describe the fuel cell stack as one would expect in a normal course. In a normal course, a reversible degradation over time is expected. Deviations from this normal course can then be recognized as malfunctions in the fuel cell stack.

[0032] According to an embodiment of the diagnostic device, the diagnostic device has a parameter monitoring module for monitoring a parameter of the fuel cell stack and for transmitting the value of the parameter to the regeneration time determination module. Due to the parameter monitoring module, it is possible to monitor a parameter that is relevant for determining the regeneration times. The parameter can be, for example, a power of the fuel cell stack, a voltage of the fuel cell stack, a time period, a number of operating hours, an amount of fuel consumed or an amount of energy produced.

[0033] Further advantages, features and details of the invention emerge from the following description, in which embodiments are described in detail with reference to the drawings. They show:

[0034] Fig. 1 is a schematic view of a diagnostic device according to the invention; and

[0035] Fig. 2 is a view of a graph of regeneration time intervals plotted against time or a function of the regeneration time intervals plotted against time.

[0036] Fig. 1 shows a schematic view of a diagnostic device 10 according to the invention. The diagnostic device 10 is used to detect malfunctions in the operation of a fuel cell stack of a fuel cell system. The diagnostic device 10 has a regeneration time point determination module 20, a regeneration time interval determination module 30, a comparison module 40 and an output module 50. Optionally, the diagnostic device 10 can also include a parameter monitoring module 60.

[0037] Several regeneration times can be determined using the regeneration time determination module 20. For this purpose, the regeneration time determination module 20 can determine a

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Determine regeneration time. Accordingly, the regeneration time determination module 20 is set up to determine the regeneration times one after the other.

[0038] The regeneration time interval determination module 30 receives the regeneration times from the regeneration time point determination module 20. The regeneration time interval determination module 30 can determine the regeneration time intervals between successive regeneration times.

[0039] The comparison module 40 receives the regeneration time intervals from the regeneration time interval determination module 30. The comparison module 40 is used to compare the regeneration time intervals with a reference. Alternatively or additionally, the comparison module 40 is used to compare a function of the regeneration time intervals with a reference function. The deviations of the regeneration time intervals from the reference and/or the deviations of the function of the regeneration time intervals from the reference function can make a disturbance in the operation of the fuel cell stack recognizable.

[0040] The output module 50 receives the comparison result from the comparison module 40. Furthermore, a fault signal can be output using the output module 50 based on the comparison result of the comparison module 40. In Fig. 1, the output of the fault signal 70 is shown with an arrow. The output of the fault signal 70 can be sent, for example, to a loudspeaker in order to be output acoustically, sent to a screen in order to enable a visual representation, or sent to a computer for further processing of the fault signal.

[0041] The diagnostic device 10 can optionally have a parameter monitoring module 60. The parameter monitoring module 60 monitors a parameter of the fuel cell stack and transmits the value of the parameter to the regeneration time determination module 20. The parameter monitoring module 60 can continuously monitor and transmit the value of the parameter. Alternatively, the parameter monitoring module 60 can also monitor and transmit the value of the parameter at specified time intervals.

[0042] The regeneration time point determination module 20 compares the value of the parameter with a previously determined target parameter value. If the value of the parameter exceeds the target parameter value, then a regeneration signal is triggered. The regeneration signal starts a regeneration cycle of the fuel cell stack, i.e. a renewal of the fuel cell stack to reverse the reversible degradation of the fuel cell stack. A regeneration time point is determined for each regeneration cycle. The regeneration times are always determined at the same point in the respective regeneration cycle. For example, the respective regeneration point can always be determined at the end of the respective fully completed regeneration cycle. However, a different point in time in the regeneration cycle is also possible.

[0043] Alternatively, in some cases, a regeneration signal can be triggered if the value of the parameter falls below a previously determined target parameter value.

[0044] The monitored parameter of the fuel cell stack may be, for example, a power of the fuel cell stack, a voltage of the fuel cell stack, a period of time, a number of operating hours, an amount of fuel consumed or an amount of energy produced.

[0045] The device described in Fig. 1 can be used in particular to carry out the following diagnostic method. The diagnostic method comprises the following steps:

[0046] In a first step, several regeneration times are determined. For each regeneration cycle of the fuel cell stack, a regeneration time is determined. The regeneration times are therefore one after the other in time.

[0047] In a second step, the regeneration time intervals are determined. A regeneration time interval is always determined for two consecutive regeneration times.

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[0048] In a third step, the regeneration time intervals are compared with a reference. Alternatively or additionally, a function of the regeneration time intervals is compared with a reference function. The comparison can be used to identify malfunctions in the operation of the fuel cell stack.

[0049] In a fourth step, a fault signal can be output based on the comparison result.

[0050] Fig. 2 shows a view of a graph. Regeneration time intervals Rl are shown, which are plotted against time t, or a function of the regeneration time intervals F{(t), which is given as a function of time t. The values of the individual regeneration time intervals RI are plotted as points in the graph. As can be seen from Fig. 2, the value of the regeneration time intervals RI decreases with time t. If the value of a regeneration time interval RI falls below the value of a reference, then a fault signal can be output.

[0051] Fig. 2 also shows a function of the regeneration time intervals F(t) which has a negative slope. The function of the regeneration time intervals F(t) can be compared with a reference function. In the event of deviations, a fault signal can be output. In particular, the slope of the function of the regeneration time intervals F(t) can be compared with the slope of a reference function.

[0052] As can be seen in Fig. 2, the function of the regeneration time intervals F(t) can be extrapolated. This extrapolation E(t) allows a diagnosis for the future course of the regeneration time intervals. This makes it possible to estimate how long the future regeneration time intervals are likely to be. This in turn makes it possible to estimate when the fuel cell stack should be renewed.

[0053] The environmental parameters of the fuel cell stack, such as temperature, air pressure, humidity, etc., can be taken into account when creating the reference and/or the reference function. Furthermore, the environmental parameters can be taken into account when creating the target parameter. The influences of the environmental parameters on the fuel cell stack can thus be eliminated.

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REFERENCE SYMBOL LIST

10 Diagnostic device 20 Regeneration time determination module 30 Regeneration time interval determination module

40 Comparison module 50 Output module

60 parameter monitoring module

70 Output of the fault signal

RI regeneration time intervals

t time

F(t) function of the regeneration time intervals

E(t) extrapolation

Claims (10)

SS N 8 N Sr 'hes AT 527 297 B1 2025-01-15 patent claims 1. Diagnostic method for detecting malfunctions in the operation of a fuel cell stack of a fuel cell system, characterized by the following steps: - determining a plurality of regeneration times, wherein a regeneration time is determined for each regeneration cycle of the fuel cell stack, and wherein the regeneration times occur one after the other, - Determining a regeneration time interval between successive regeneration times, - comparing the regeneration time intervals with a reference and/or comparing a function of the regeneration time intervals with a reference function in order to detect disturbances in the operation of the fuel cell stack, and - Outputting a fault signal based on the comparison result, characterized in that the reference is created by previously determined regeneration time intervals, and the fault signal is output if a regeneration time interval has a deviation compared to the reference which is above a limit value. 2. Diagnostic method according to claim 1, characterized in that each regeneration time is determined by continuously monitoring a parameter of the fuel cell stack, and a regeneration signal is triggered when a value of the parameter falls below or exceeds a target barometer value. 3. Diagnostic method according to claim 2, characterized in that the parameter is a power of the fuel cell stack, a voltage of the fuel cell stack, a time period, a number of operating hours, an amount of fuel consumed or an amount of energy produced. 4. Diagnostic method according to claim 2 or 3, characterized in that the respective regeneration signal triggers a regeneration cycle of the fuel cell stack, and each regeneration time is the respective end time of the regeneration cycle of the fuel cell stack. 5. Diagnostic method according to one of the preceding claims, characterized in that the function of the regeneration time intervals is created as a time course of the determined regeneration time intervals, and a slope of the function is calculated, wherein an interference signal is output if the calculated slope is above or below a limit value. 6. Diagnostic method according to one of the preceding claims, characterized in that the function of the regeneration time intervals is extrapolated as a temporal course of the determined regeneration time intervals in order to create a diagnosis for the future course of the regeneration time intervals. 7. Diagnostic method according to one of the preceding claims, characterized in that one or more environmental parameters are taken into account when creating the reference or the reference function. 8. Computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the steps of a diagnostic method having features of one of claims 1 to 7. 9. Diagnostic device (10) for detecting malfunctions in the operation of a fuel cell stack of a fuel cell system, comprising a regeneration time determination module (20) for determining a plurality of regeneration times, wherein a regeneration time can be determined for each regeneration cycle of the fuel cell stack, and wherein the regeneration time determination tuning module (20) is set up to determine the regeneration times one after the other, a regeneration time interval determination module (30) for determining a regeneration time interval between successive regeneration times, a comparison module (40) for comparing the regeneration time intervals with a reference and/or comparing a function of the regeneration time intervals with a reference function in order to detect disturbances in the operation of the fuel cell stack, and an output module (50) for outputting a fault signal based on the comparison result of the comparison module (40), characterized in that the regeneration time point determination module (20) and/or the regeneration time interval determination module (30) and/or the comparison module (40) and/or the output module (50) are designed to carry out the method according to one of claims 1 to 7. 10. Diagnostic device (10) according to claim 9, characterized in that the diagnostic device (10) has a parameter monitoring module (60) for monitoring a parameter of the fuel cell stack and for transmitting the value of the parameter to the regeneration time determination module (20). Here 2 sheets of drawings