Diagnosis method for detecting disturbances in a fuel cell stack

Abstract

The present invention relates to a diagnosis method for detecting disturbances in the operation of a fuel cell stack of a fuel cell system, comprising the following steps: - determining multiple regeneration times, a regeneration time being determined for a respective regeneration cycle of the fuel cell stack, and the regeneration times being at successive times, - determining a respective 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 disturbance signal on the basis of the comparison result. The reference in this case is produced by previously determined regeneration time intervals, and the disturbance signal is output if, compared to the reference, a regeneration time interval has a difference that is above a limit value.

Description

[0001] Diagnostic procedure for detecting faults in a fuel cell stack

[0002] 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.

[0003] 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 what portion of the degradation is reversible and what portion is irreversible, or which malfunctions occur. Irreversible degradation accounts for some of the malfunctions that can occur in a fuel cell stack. In addition, other malfunctions of the fuel cell stack can also occur.

[0004] Against this background, one object of the present invention is to at least partially remedy the disadvantages described above. In particular, the object of the present invention is to determine faults in a fuel cell stack.

[0005] The above object is achieved by a diagnostic method having the features of claim 1, a computer program product having the features of claim 10, and a diagnostic device having the features of claim 11. Further features and details of the invention emerge from the 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 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 always made to each other.

[0006] 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:

[0007] - 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 are successive in time,

[0008] - Determining a regeneration time interval between successive regeneration times,

[0009] - 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

[0010] - Outputting a fault signal based on the comparison result.

[0011] By comparing the regeneration time intervals with a reference and / or comparing a function of the regeneration time intervals with a reference function, it is possible to determine whether the regeneration time intervals are changing in a way that can only be explained by a fault. This allows for the detection of malfunctions in the operation of the fuel cell stack.

[0012] A regeneration cycle represents a renewal of the fuel cell stack to reverse its reversible degradation. The regeneration times can be determined as follows: A parameter, such as power or voltage, falls below an operating-point-dependent limit at a specific operating point. If, for example, the voltage has fallen below the limit, then the fuel cell stack needs to be renewed. A regeneration time is determined for each fully completed renewal.

[0013] The regeneration time interval represents the time between two consecutive regeneration points. Furthermore, the regeneration time interval can range from 1 day to 20 weeks, from 1 week to 10 weeks, and especially from 4 weeks to 8 weeks. However, especially in stationary operation, the regeneration interval can also be in the range of minutes.

[0014] The regeneration cycle, ie the renewal of the fuel cell stack, can range from 1 minute to 200 minutes, from 10 minutes to 150 minutes, and in particular from 30 minutes to 90 minutes.

[0015] The expression "wherein a regeneration time is determined during each regeneration cycle of the fuel cell stack" can mean that the regeneration time is determined at any point in time during 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.

[0016] It is particularly advantageous to always determine the point in time when reversible regeneration has been fully completed. However, 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, as it cannot be reliably determined what proportion of the reversible degeneration was actually eliminated, and this then influences the time interval between two regenerations.

[0017] The reference can represent the regeneration time interval that can be expected under normal conditions for reversible degradation of the fuel cell stack. As discussed previously, the regeneration time interval is highly dependent on the operation of the fuel cell, particularly the operating point and whether dynamic or steady-state operation is taking place. A deviation of a specific regeneration time interval from the reference can therefore result in a disruption of the operation of the fuel cell stack.

[0018] The reference function can represent a target function that is to be expected in the event of reversible degradation of the fuel cell stack that is to be expected under normal circumstances. The target function specifies the expected regeneration time intervals over time. A deviation of the function of the regeneration time intervals from the reference function can then accordingly mean a disruption in the operation of the fuel cell stack. In the present application, a fuel cell system is understood to be a system (e.g. SOFC: Solid Oxide Fuel Cell) that has fuel cells for generating electrical energy using a fuel, or a system (e.g. SOEC: Solid Oxide Electrolyzer Cell) that 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 procedure can be particularly relevant for stationary applications and continuously operated fuel cell systems.

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

[0021] According to another embodiment of the diagnostic method, 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, a quantity of fuel consumed, or a quantity of energy produced. All of these parameters are suitable for monitoring the fuel cell stack. However, other parameters may also be used. The time period may 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. According to a further embodiment of the diagnostic method, an environmental parameter is taken into account when determining the target parameter 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 determining the target parameter value. Alternatively, several environmental parameters can be considered simultaneously.

[0023] According to the invention, the reference is established using previously determined regeneration time intervals. The fault signal is output if a regeneration time interval differs from the reference by more than a limit value. The regeneration time interval compared with the reference can, in particular, be the most recently determined regeneration time interval. This allows, in particular, short-term faults in the fuel cell stack to be detected. 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 calculated for the previously determined regeneration time intervals.

[0024] 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. A gradient of the function is calculated, with a disturbance signal being output if the calculated gradient lies above or below a limit value. The gradient is a derivative of the function with respect to time. The gradient can also be determined from only one region of the function, e.g., in particular from an end region. This is particularly necessary if a uniform gradient cannot be determined over the entire course of the function. The calculated gradient can be used to detect whether there is a disruption in the operation of the fuel cell stack.

[0025] 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.

[0026] 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, air pressure, or 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, multiple environmental parameters can be considered simultaneously.

[0027] Furthermore, the present invention relates to a computer program product comprising instructions which, when executed by a computer, cause the computer to perform the steps of a diagnostic method according to the invention. Thus, a computer program product according to the invention also provides the same advantages as those explained in detail with reference to a diagnostic method according to the invention.

[0028] Furthermore, a diagnostic device for detecting malfunctions in the operation of a fuel cell stack of a fuel cell system is provided. The diagnostic device comprises a regeneration time determination module 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 module is configured to determine the regeneration times sequentially; 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 malfunctions 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, characterized in that the regeneration time point determination module and / or the regeneration time interval determination module and / or the comparison module and / or the output module are designed to carry out the method according to one of claims 1 to 7.

[0029] Preferably, the regeneration time point determination module, the regeneration time interval determination module, the comparison module and the output module are designed to carry out a diagnostic method according to the invention.

[0030] 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 identify malfunctions in the operation of the fuel cell stack. The reference or the reference function describe the fuel cell stack as expected under normal conditions. Under normal conditions, reversible degradation is expected over time. Deviations from this normal course can then be identified as malfunctions in the fuel cell stack.

[0031] According to one embodiment of the diagnostic device, the diagnostic device comprises 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. The parameter monitoring module makes it possible to monitor a parameter relevant for determining the regeneration times. The parameter can be, for example, a power output 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.

[0032] Further possible implementations of the invention also include combinations of features described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0033] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments are described in detail with reference to the drawings. In the drawings: Fig. 1 shows a schematic view of a diagnostic device according to the invention; and

[0034] 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.

[0035] Fig. 1 shows a schematic view of a diagnostic device 10 according to the invention. The diagnostic device 10 serves to detect malfunctions in the operation of a fuel cell stack of a fuel cell system. The diagnostic device 10 comprises a regeneration time 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.

[0036] The regeneration time determination module 20 can determine multiple regeneration times. For this purpose, the regeneration time determination module 20 can determine a regeneration time for each regeneration cycle, ie, for each renewal of the fuel cell stack. Accordingly, the regeneration time determination module 20 is configured to determine the regeneration times sequentially.

[0037] 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.

[0038] The comparison module 40 receives the regeneration time intervals from the regeneration time interval determination module 30. The comparison module 40 serves to compare the regeneration time intervals with a reference. Alternatively or additionally, the comparison module 40 serves 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 malfunction in the operation of the fuel cell stack recognizable. The output module 50 receives the comparison result from the comparison module 40. Furthermore, a malfunction signal can be output based on the comparison result of the comparison module 40 with the output module 50. In Fig. 1, the output of the malfunction signal 70 is shown with an arrow. The output of the malfunction signal 70 can, for example,to a loudspeaker for acoustic output, sent to a screen to enable visual representation, or sent to a computer for further processing of the interference signal.

[0039] The diagnostic device 10 can optionally include a parameter monitoring module 60. The parameter monitoring module 60 monitors a parameter of the fuel cell stack and transmits the parameter value to the regeneration time determination module 20. The parameter monitoring module 60 can continuously monitor and transmit the parameter value. Alternatively, the parameter monitoring module 60 can also monitor and transmit the parameter value at specified intervals.

[0040] The regeneration time-point determination module 20 compares the parameter value with a previously determined target parameter value. If the parameter value exceeds the target parameter value, 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 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 the regeneration cycle is also possible.

[0041] Alternatively, in some cases, a regeneration signal can be triggered if the value of the parameter falls below a previously determined target parameter value.

[0042] The monitored parameter of the fuel cell stack 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.

[0043] The device described in Fig. 1 can be used to carry out, in particular, the following diagnostic procedure. The diagnostic procedure comprises the following steps:

[0044] In a first step, several regeneration points are determined. A regeneration point is determined for each regeneration cycle of the fuel cell stack. Thus, the regeneration points occur one after the other in time.

[0045] In a second step, the regeneration time intervals are determined. A regeneration time interval is always determined for two consecutive regeneration times.

[0046] 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. This comparison can be used to detect malfunctions in the operation of the fuel cell stack.

[0047] In a fourth step, a fault signal can be output based on the comparison result.

[0048] Fig. 2 shows a view of a graph. It shows regeneration time intervals RI plotted against time t, or a function of the regeneration time intervals F(t), which is specified 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 reference value, a fault signal can be output.

[0049] Fig. 2 further 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. 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 replaced.

[0050] 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. This allows the influence of the environmental parameters on the fuel cell stack to be eliminated.

[0051] List of reference symbols

[0052] 10 Diagnostic device

[0053] 20 Regeneration time point determination module

[0054] 30 Regeneration time interval determination module

[0055] 40 Comparison module

[0056] 50 output module

[0057] 60 Parameter Monitoring Module

[0058] 70 Output of the fault signal

[0059] RI Regeneration time intervals t time

[0060] F(t) function of the regeneration time intervals

[0061] E(t) Extrapolation

Claims

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 are successive in time, - 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 if a value of the parameter falls below or exceeds a target parameter 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 consumed fuel or an amount of produced energy.

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 gradient of the function is calculated, wherein an interference signal is output if the calculated gradient 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. A 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 any 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 in each regeneration cycle of the fuel cell stack, and wherein the regeneration time determination module (20) is configured 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 disturbance 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).

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