Method for operating an electrochemical device, open-loop or closed-loop control device, and electrochemical device

Abstract

The invention proceeds from a method for operating an electrochemical device, in particular a fuel cell device, wherein, in at least one method step, at least one operating parameter and at least one further operating parameter, which is different from the operating parameter, for open-loop or closed-loop control of the electrochemical device are measured and wherein, in at least one method step, it is determined that a steady operating state (14) of the electrochemical device has been reached. It is proposed that a time profile of an, in particular individual, operating characteristic variable combining the at least one operating parameter and the at least one further operating parameter is evaluated in order to identify that the steady operating state (14) has been reached.

Description

[0001] Description

[0002] Method for operating an electrochemical device, control or regulating device and electrochemical device

[0003] State of the art

[0004] A method for operating an electrochemical device, in particular a fuel cell device, has already been proposed, in which in at least one method step at least one operating parameter and at least one further operating parameter different from the operating parameter are detected for controlling or regulating the electrochemical device and wherein in at least one method step it is determined that a steady-state operating state of the electrochemical device has been reached.

[0005] Disclosure of the invention

[0006] The invention is based on a method for operating an electrochemical device, in particular a fuel cell device, wherein in at least one method step at least one operating parameter and at least one further operating parameter different from the operating parameter are detected for controlling or regulating the electrochemical device and wherein in at least one method step it is determined that a steady-state operating state of the electrochemical device has been reached.

[0007] It is proposed that a temporal profile of an operating parameter, in particular an individual operating parameter, which summarizes the at least one operating parameter and the at least one further operating parameter is evaluated in order to detect when the steady-state operating state has been reached. The electrochemical device preferably comprises at least one electrochemical conversion unit for electrochemically converting at least one reactant fluid into at least one product fluid. Particularly preferably, the electrochemical conversion unit comprises at least one fuel cell for electrochemically converting a fuel, in particular hydrogen and / or natural gas, with the addition of oxygen and the provision of electrical energy. The at least one fuel cell preferably converts an oxygen-containing fluid as reactant fluid into an oxygen-poor exhaust gas as product fluid.Preferably, the at least one fuel cell converts the fuel as a further reactant fluid into a fuel-lean exhaust gas as a further product fluid. The terms "fuel-lean" and "oxygen-lean" refer to a fuel or oxygen content in the respective product fluid relative to the respective reactant fluid. Alternatively, the electrochemical conversion unit comprises at least one electrolyzer, for example for splitting water as a reactant fluid into hydrogen and oxygen as product fluids while absorbing electrical energy. The electrochemical device preferably comprises at least one sensor unit for detecting the operating parameter and / or the further operating parameter.

[0008] The sensor unit detects, as operating parameters and / or as further operating parameters, for example, an electrical parameter of the electrochemical conversion unit, a thermal parameter of the electrochemical conversion unit, the product fluid and / or the reactant fluid, a flow parameter of the product fluid and / or the reactant fluid, or the like. The electrical parameter is, for example, an electrical current provided or consumed by the electrochemical conversion unit and / or an electrical power provided or consumed by the electrochemical conversion unit and / or an electrical voltage applied to the electrochemical conversion unit. The thermal parameter is, for example, a temperature or heat quantity of the reactant fluid upon entering the electrochemical conversion unit or a temperature or heat quantity of the product fluid upon exiting the electrochemical conversion unit.The flow parameter is, for example, a volume flow, a molar flow, a particle flow, or a mass flow of the product fluid or the reactant fluid, a pressure or a pressure difference within the reactant fluid or the product fluid, or the like. Preferably, a control or regulating device of the fuel cell device determines the operating parameter as a function of the operating parameter and as a function of the further operating parameter, in particular as a function of more than two operating parameters. The operating parameter is preferably dependent on an overall state of the electrochemical device. Particularly preferably, the operating parameter is dependent on at least one electrical operating parameter, at least one thermal operating parameter, and / or at least one flow parameter of the electrochemical device.Particularly preferably, the operating parameter is a physical and / or chemical quantity or characteristic value, for example an electrical voltage, a temperature, an energy or the like. Alternatively, the operating parameter is an abstract function without physico-chemical meaning, for example a result of a scoring system. Particularly preferably, the control or regulating device only evaluates the operating parameter and, in particular depending on a configuration of the method, optionally a time in order to decide whether the electrochemical device is in a stationary or a transient operating state. Particularly preferably, the control or regulating device detects the stationary operating state by the fact that the operating parameter changes only insignificantly. In particular, the control or regulating device detects transient operation by the fact that the operating parameter changes significantly.The control or regulating device preferably determines a significant change and / or an insignificant change in the operating parameter by comparing a change variable characterizing or describing the temporal progression of the operating parameter with a threshold value. The change variable can be embodied, for example, as a differential, as a difference quotient, as the difference between successive determined values ​​of the operating parameter, in particular as a measure of dispersion, or the like. The control or regulating device preferably determines a plurality of values ​​of the operating parameter within a time window. Particularly preferably, the control or regulating device determines values ​​of the operating parameter continuously, in particular at predetermined regular time intervals or in real time.“Real time” is to be understood here as time intervals that are only limited by the data processing speed of the control or regulating device. Alternatively, the control or regulating device limits the determination of a value of the operating parameter to one every 10 milliseconds, in particular to one every 50 milliseconds. Particularly preferably, the control or regulating device determines at least one value of the operating parameter in 10 minutes, preferably at least one value of the operating parameter per minute, particularly preferably at least one value of the operating parameter in 10 seconds, and most preferably at least one value of the operating parameter per second. The control or regulating device preferably determines the change variable as a function of several values, preferably the majority of the values, in particular all values ​​of the operating parameter that are determined within the time window.Optionally, the control or regulating device excludes individual values ​​of the operating parameter determined within the time window from further processing into the change variable, for example, due to a plausibility check or the like. The control or regulating device preferably determines the change variable as a function of more than three, particularly preferably more than five, particularly preferably more than ten, values ​​of the operating parameter, which were determined in particular at different times within the time window.

[0009] The control or regulating device is preferably designed to bring about the steady-state operating state by changing the operating parameters. In particular, in the transient operating state or upon a change in operating point, the control or regulating device controls at least one actuating unit of the electrochemical device in order to change at least one of the operating parameters and / or an additional, unmonitored operating parameter of the electrochemical device. The actuating unit is, for example, a conveying unit, in particular a pump, a compressor, a blower, or the like, for adjusting the flow parameter and / or the thermal parameter. The actuating unit is, for example, an inverter or an adjustable resistor for adjusting the electrical parameter. Preferably, the control or regulating device switches to a monitoring and / or analysis mode upon reaching the steady-state operating state.The monitoring and / or analysis mode is preferably provided to maintain the steady-state operating state and optionally to evaluate an actual value of at least one of the operating parameters in the steady-state operating state for an operational analysis of the electrochemical device, for example to analyze the reactant fluid, to detect degradation of the electrochemical conversion unit, to record an efficiency of the electrochemical device or the like.

[0010] The inventive design advantageously allows for easy detection of a steady-state operating state. In particular, the definition of a large number of criteria, threshold values, time constants, or the like for each individual operating parameter can be dispensed with. Furthermore, a waiting time after a load change to ensure that a steady-state operating state exists can advantageously be kept short. In particular, during a load change, it is possible to specifically wait for the steady-state operating state to settle. This allows for advantageously robust system dynamics. The method is advantageously robust and, at the same time, advantageously simple in implementation and allows simple interpretation of the operating parameter. Furthermore, extended control and regulation functions as well as soft sensor concepts, which are based, for example, on energy balances and are therefore only valid in the steady-state operating state, can advantageously be reliably implemented.In particular, this provides an advantageously comprehensive analysis option for the behavior of the electrochemical device. Furthermore, a advantageously high storage and computing efficiency of the control or regulating device can be achieved, since a combined variable is used for monitoring instead of a multitude of individual operating parameters.

[0011] It is further proposed that the operating parameter summarizes at least one electrical parameter, one flow parameter, and one thermal parameter of the electrochemical device as an operating parameter in order to detect the achievement of the steady-state operating state. Particularly preferably, the control or regulating device determines the operating parameter, in particular without an additional sensor, as a function of standard sensor data from the sensor unit, which are acquired for controlling or regulating the electrochemical device. The control or regulating device determines the operating parameter K, for example, using the following calculation rule: where I ei the electric current generated by the electrochemical conversion unit, U Ze u en one with the generated current I ei associated electrical voltage of the electrochemical conversion unit, N Ze u enthe number of fuel cells or electrolyzers in the electrochemical conversion unit, where F is the Faraday constant, h aus a molar enthalpy of the product fluid upon exiting the electrochemical conversion unit, h ein a molar enthalpy of the reactant fluid upon entry into the electrochemical conversion unit and n ein a material flow of the reactant fluid. The electrical parameters, ie the current I ei and the electrical voltage U Ze u en , are preferably recorded by the sensor unit. The flow parameter, ie the material flow n ein , is preferably detected by the sensor unit or determined from a volume flow or mass flow detected by the sensor unit. The molar enthalpies h aus , h einare determined by the control or regulating device preferably as a function of a temperature of the reactant fluid or the product fluid detected by the sensor unit. Regression functions for the molar enthalpies h are preferably stored in a memory of the control or regulating device. aus , h ein depending on the temperature of the reactant fluid or the product fluid, which the control or regulating device uses to determine the molar enthalpies h aus , h einto determine. The control or regulating device preferably uses the oxygen-containing fluid as the reactant fluid and the low-oxygen exhaust gas as the product fluid to determine the operating parameter. The inventive design advantageously allows relevant operating parameters to be physically linked to evaluate an operating state of the electrochemical device. In particular, a single physically interpretable variable can be used to monitor the operating state. A parameterization of criteria that allow inferences to be drawn from the operating parameter to the operating state only needs to be created for the one operating parameter and not for each operating parameter.

[0012] It is further proposed that in at least one method step of the method, a measure of dispersion of the operating parameter is evaluated in order to detect when the steady-state operating state has been reached. The control or regulating device preferably evaluates the values ​​of the operating parameter determined in the time window in order to determine the measure of dispersion. The time window is preferably a sliding time window. The control or regulating device preferably updates the time window regularly, in particular with each newly determined value of the operating parameter. The measure of dispersion can be, for example, the sum of the squares of the deviations, the empirical variance, the empirical standard deviation, the coefficient of variation, the mean absolute deviation from a mean value, a quantile distance or the like of the values ​​of the operating parameter determined in the time window.The mean value of the operating characteristic can be the arithmetic mean, the geometric mean, the median, or another mean value of the operating characteristic. Preferably, the control or regulating device evaluates a determined value of the dispersion measure to decide, in particular independently of the mean value of the operating characteristic, whether the electrochemical device is in a steady-state operating state or in a transient operating state. Preferably, the control or regulating device decides that the electrochemical device is in a steady-state operating state if the dispersion measure is less than a threshold value. The threshold value can be defined absolutely or relative to the mean value.Preferably, the control or regulating device determines that the electrochemical device is in a transient operating state if the degree of variation is greater than the threshold value or a further threshold value different from the threshold value. Alternatively, the control or regulating device evaluates the operating parameter using wavelet transformation to detect when the steady-state operating state has been reached. The inventive design advantageously allows for a simple evaluation of the operating parameter over time.

[0013] It is further proposed that the empirical variance of the operating parameter be used as a measure of dispersion in at least one step of the method. The empirical variance can be determined as the sum of the squared deviations divided by the number of degrees of freedom (corrected empirical variance) or divided by the number of values ​​in the time window (uncorrected empirical variance). The inventive design allows for a simple and advantageous evaluation of the operating parameter over time.

[0014] It is further proposed that at least two values ​​of the operating parameter, which are used to decide whether the steady-state operating state exists or not, are more than 10 minutes apart. The time window can be defined directly via the duration of time, in particular if the values ​​of the operating parameter are stored with a timestamp, and / or via a number of values ​​of the operating parameter, in particular if these are recorded at regular intervals. The time window preferably comprises at least 10 minutes, preferably at least 20 minutes, particularly preferably at least 30 minutes. The control or regulating device preferably stores all determined values ​​of the operating parameter in the time window. The control or regulating device preferably stores at most a predetermined maximum number of values ​​of the operating parameter, which is preferably defined by the time window.When the maximum number of values ​​of the reference parameter is reached, a stored value of the operating parameter is replaced for each newly determined value of the operating parameter, preferably according to the first-in, first-out (FIFO) principle. The inventive design allows for a reliable assessment of whether the operating state is steady or transient.

[0015] It is further proposed that in at least one method step of the method, an exponentially smoothed average of the operating characteristic is determined. Preferably, the control or regulating device determines the mean value of the operating characteristic as an exponentially smoothed average based on all values ​​determined in the time window. Preferably, the control or regulating device determines the dispersion measure as a function of the exponentially smoothed average. Preferably, the control or regulating device updates the dispersion measure recursively. Preferably, the control or regulating device determines for each newly determined value of the operating parameter a deviation 8i of the newly determined value of the operating parameter from a previous value of the exponentially smoothed average in particular in accordance with

[0016] Preferably, the control or regulating device updates the exponentially smoothed average K ema i by adding the deviation <5; of the newly determined value of the operating parameter to the previous value of the exponentially smoothed average K^-i, whereby the deviation is subjected to a smoothing factor a, in particular according to

[0017] ^ema,i Ct ' 8t + Kema,i~l Preferably, the control or regulating device determines an updated value of the dispersion measure var K) ema i depending on the smoothing factor a, a previous value of the dispersion measure var K') ema ^1and the deviation 6 of the newly determined value of the operating parameter, in particular according to

[0018] The smoothing factor is preferably between 0 and 1. Preferably, the control or regulating device determines an initial value of the dispersion measure var(K) ema 0non-recursively, in particular by means of an explicit form of the measure of dispersion, such as the sum of the squares of the deviations. As the initial value of the operating parameter K ema 0 The control or regulating device can use the arithmetic mean, the geometric mean, the median of the values ​​of the operating characteristic in the time window, a specific value of the determined values ​​of the operating characteristic, for example, the first value, the last value, or the like, or a randomly selected value of the operating characteristic. The inventive design advantageously minimizes the memory consumption and / or the computing power required by the control or regulating device to detect the steady-state operating state.

[0019] It is further proposed that, in at least one method step of the method, a smoothing factor for determining the exponentially smoothed average be selected as a function of a relaxation time of the electrochemical device. The time window is preferably longer than the relaxation time of the electrochemical device. The smoothing factor is preferably determined as a function of a ratio of the relaxation time to the duration of the time window. The relaxation time of the electrochemical device depends on a heat capacity of the electrochemical conversion unit and, in particular, indicates how quickly a temperature of the electrochemical conversion unit approaches a new equilibrium temperature, in particular exponentially, upon intentional or disturbance-induced departure from the steady-state operating state.The inventive design allows a relationship between the significance of past values ​​and current values ​​of the operating parameter in the exponentially smoothed average to be advantageously linked to a dynamic relevant to the electrochemical device. It is further proposed that, in at least one method step of the method, the temporal progression of the operating parameter until the steady-state operating state is reached is evaluated to assess the condition of the electrochemical device. The condition assessment may, for example, include a fault analysis, a service life prognosis, and / or a determination of the degree of degradation of the electrochemical device by the control or regulating device or an external computing unit.Preferably, upon detecting the steady state, the control or regulating device outputs a signal indicating that the steady state has been reached, so that a state assessment dependent on a steady state can be initiated by the external computing unit. Additionally or alternatively, the control or regulating device directly evaluates the temporal progression of the operating parameter to perform a state assessment. For example, the control or regulating device or the external computing unit determines a duration until the steady state operating state is reached, an amplitude of an overshoot or an asymptotic creep behavior of the operating parameter, an attenuation of the amplitude of the overshoot of the operating parameter, an average value of the operating parameter upon reaching the steady state operating state, or the like.Alternatively or additionally, the control or regulating device stores and / or transmits the temporal progression of the operating parameter for evaluation by a maintenance technician and / or an external computing device, for example, a server on which a machine learning process for condition assessment has been implemented. The inventive design advantageously provides many additional parameters for a condition assessment. Furthermore, a starting time for the condition assessment can advantageously be reliably selected in the steady-state operating state.

[0020] Furthermore, a control or regulating device for an electrochemical device for carrying out a method according to the invention is proposed. The control or regulating device is provided for controlling or regulating the electrochemical device. The control or regulating device is preferably a unit with at least one control electronics unit. The term "control electronics" should be understood in particular as a unit with a processor unit and with a memory as well as with an operating program stored in the memory. The embodiment according to the invention makes it possible to provide a control or regulating device which can advantageously reliably detect a steady-state operating state with an advantageously low memory and / or computing requirement.

[0021] Furthermore, an electrochemical device, in particular a fuel cell device, with at least one electrochemical conversion unit and with at least one control or regulating device according to the invention is proposed. The electrochemical conversion unit preferably comprises at least one fuel cell or one electrolyzer, preferably a stack of, in particular identical, fuel cells or electrolyzers, or a combination of several stacks of, in particular identical, fuel cells or electrolyzers. The at least one fuel cell is preferably designed as a high-temperature fuel cell, in particular a solid oxide fuel cell or a molten carbonate fuel cell. Alternatively, the fuel cell is a phosphoric acid fuel cell, a direct methanol fuel cell, or a polymer electrolyte membrane fuel cell.The at least one electrolyzer is preferably designed as a high-temperature electrolyzer, in particular as a solid oxide electrolyzer cell.

[0022] The electrochemical device preferably comprises at least one reactant fluid delivery unit or one reactant fluid shut-off device for adjusting an inflow rate of fresh reactant fluid to the electrochemical conversion unit. The reactant fluid delivery unit or the reactant fluid shut-off device are preferably controlled by the control or regulating device to set the steady-state operating state. The electrochemical device preferably comprises at least one inverter and / or an adjustable resistor for adjusting the electrical parameter. The inverter and / or the adjustable resistor are preferably controlled by the control or regulating device to set the steady-state operating state. The electrochemical device preferably comprises the sensor unit for detecting the operating parameters of the electrical device.The sensor unit comprises, for example, at least one temperature sensor upstream of the electrochemical conversion unit. The sensor unit comprises, for example, at least one further temperature sensor downstream of the electrochemical conversion unit and / or in or on the electrochemical conversion unit. The sensor unit comprises, for example, an ammeter and / or a voltmeter for detecting the electrical parameter. The sensor unit preferably comprises at least one flow meter for detecting the flow parameter.

[0023] In particular, when designed as a fuel cell device, the electrochemical device optionally comprises an afterburner for utilizing fuel residues in the fuel-poor exhaust gas, a desulfurizer and / or a reformer for processing the fuel, a heat exchanger for transferring heat from a product fluid to the reactant fluid and / or a recirculation line for feeding the product fluid back into the reactant fluid.

[0024] The configuration according to the invention makes it possible to provide an electrochemical device whose operating state can be determined during operation of the electrochemical device advantageously promptly, in particular in real time, advantageously reliably and advantageously in a resource-saving manner.

[0025] The method according to the invention, the control or regulating device according to the invention, and / or the electrochemical device according to the invention are not intended to be limited to the application and embodiment described above. In particular, the method according to the invention, the control or regulating device according to the invention, and / or the electrochemical device according to the invention can have a number of individual elements, components, units, and method steps that differs from the number stated herein in order to fulfill a function described herein. Furthermore, in the value ranges specified in this disclosure, values ​​within the stated limits are also to be considered disclosed and can be used arbitrarily.

[0026] Drawings

[0027] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an exemplary embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0028] They show:

[0029] Fig. 1 is a schematic representation of an electrochemical device according to the invention and

[0030] Fig. 2 is a schematic flow diagram of a method according to the invention.

[0031] Description of the embodiment

[0032] Figure 1 shows an electrochemical device 12. The electrochemical device 12 is designed, for example, as a fuel cell device. The electrochemical device 12 preferably comprises at least one electrochemical conversion unit 18. The electrochemical conversion unit 18 comprises at least one fuel cell, preferably a plurality of fuel cells, which are particularly preferably arranged in at least one stack. For the sake of clarity, the electrochemical conversion unit 18 is functionally illustrated here as a single fuel cell. The electrochemical conversion unit 18, in particular each fuel cell of the electrochemical conversion unit 18, comprises at least one oxygen electrode 20 and at least one fuel electrode 22. The oxygen electrode 20 is provided for direct contact with an oxygen-containing fluid as the reactant fluid.The oxygen electrode 20 preferably outputs a low-oxygen exhaust gas as a product fluid. The fuel electrode 22 is provided for direct contact with a fuel as a further reactant fluid. The fuel electrode 22 preferably outputs a low-fuel exhaust gas as a further product fluid. The electrochemical device 12 preferably comprises an inverter 48, which is electrically connected to the oxygen electrode 20 and the fuel electrode 22. Particularly preferably, the at least one fuel cell, in particular all fuel cells of the electrochemical conversion unit 18, is designed as a solid oxide fuel cell (SOFC).

[0033] The electrochemical device 12 preferably comprises a reactant fluid delivery unit 24, in particular a fan, a blower, or a compressor, for conveying the oxygen-containing fluid to the oxygen electrode 20. The oxygen-containing fluid is particularly preferably ambient air, which is drawn in by the reactant fluid delivery unit 24. Alternatively, the oxygen-containing fluid is an industrial gas with a defined oxygen content. The reactant fluid delivery unit 24 is arranged upstream of the oxygen electrode 20 with respect to the oxygen-containing fluid.

[0034] The electrochemical device 12 preferably comprises a further reactant fluid delivery unit 26, in particular a fan, a blower, or a compressor, for conveying the fuel to the fuel electrode 22. The fuel is preferably hydrogen and / or natural gas. Alternatively, the fuel comprises at least one hydrocarbon as a pure substance or as a mixture and / or ammonia. The further reactant fluid delivery unit 26 is arranged upstream of the fuel electrode 22 with respect to the fuel. The electrochemical conversion unit 18 is preferably provided for providing electrical energy by converting the fuel into the further product fluid by supplying oxygen from the oxygen-containing fluid.

[0035] Optionally, the electrochemical device 12 comprises a desulfurizer 28. The desulfurizer 28 is preferably arranged downstream of the further reactant fluid delivery unit 26 and upstream of the electrochemical conversion unit 18 with respect to the further reactant fluid. Optionally, the electrochemical device 12 comprises a reformer 30 for reforming the further reactant fluid. The reformer 30 is preferably arranged downstream of the further reactant fluid delivery unit 26 with respect to the further reactant fluid, in particular downstream of the desulfurizer 28, and upstream of the electrochemical conversion unit 18.The electrochemical device 12 preferably comprises a recirculation line 34 and a recirculation conveying unit 36, in particular a fan, a blower or a compressor, arranged in or on the recirculation line 34, for returning the further product fluid emerging from the fuel electrode 22 into the further reactant fluid upstream of the fuel electrode 22. A feed opening of the recirculation line 34 is preferably arranged upstream of the reformer 30 and downstream of the desulfurizer 28 with respect to the further reactant fluid.

[0036] The electrochemical device 12 preferably comprises an afterburner 32 for converting fuel residues contained in the further product fluid. The afterburner 32 is preferably arranged downstream of the fuel electrode 22 with respect to the further product fluid and in particular downstream of a branch into the recirculation line 34. The afterburner 32 is preferably arranged downstream of the oxygen electrode 20 with respect to the product fluid. The electrochemical device 12 preferably comprises a heat exchanger 38 for transferring heat from an afterburner exhaust gas of the afterburner 32 exiting from the afterburner 32 to the reactant fluid upstream of the electrochemical conversion unit 18. The heat exchanger 38 is preferably arranged downstream of the reactant fluid conveying unit 24 and upstream of the electrochemical conversion unit 18 with respect to the reactant fluid.The electrochemical device 12 preferably comprises a further heat exchanger 40 for transferring heat from the afterburner exhaust gas of the afterburner 32 exiting the afterburner 32 to the further reactant fluid upstream of the electrochemical conversion unit 18. The further heat exchanger 40 is preferably arranged downstream of the desulfurizer 28 and upstream of the feed opening of the recirculation line 34 with respect to the further reactant fluid. The further heat exchanger 40 is arranged here, for example, downstream of the heat exchanger 38 with respect to the afterburner exhaust gas. Alternatively, the heat exchanger 38 is arranged downstream of the further heat exchanger 40 with respect to the afterburner exhaust gas.

[0037] The electrochemical device 12 comprises at least one control or regulating device 16. The control or regulating device 16 is preferably provided for controlling the reactant fluid conveying unit 24, the further reactant fluid conveying unit 26, and the recirculation conveying unit 36 ​​in order to adjust a flow parameter of the reactant fluid and / or the further reactant fluid through the electrochemical conversion unit 18. The control or regulating device 16 is preferably provided for controlling the inverter 48 in order to adjust an electrical parameter of the electrochemical conversion unit 18. The control or regulating device 16 is provided for carrying out a method 10, which is explained in more detail in the following Figure 2.

[0038] The electrochemical device 12 comprises at least one sensor unit. The sensor unit preferably comprises a flow meter 42 for detecting the flow parameter of the reactant fluid. The flow meter 42 is preferably arranged downstream of the reactant fluid conveying unit 24 and upstream of the electrochemical conversion unit 18, in particular of the heat exchanger 38. Alternatively, the control or regulating device 16 determines the flow parameter from a conveying capacity, in particular a rotational speed, of the reactant fluid conveying unit 24. The sensor unit preferably comprises at least one inlet temperature sensor 44 for detecting an inlet temperature of the reactant fluid upon entry into the electrochemical conversion unit 18. The inlet temperature sensor 44 is preferably arranged upstream of the electrochemical conversion unit 18 and downstream of the reactant fluid conveying unit 24, in particular of the heat exchanger 38.The sensor unit preferably comprises at least one outlet temperature sensor 46 for detecting an outlet temperature of the product fluid upon exiting the electrochemical conversion unit 18. The outlet temperature sensor 46 is preferably arranged downstream of the electrochemical conversion unit 18 and upstream of the afterburner 32. The control or regulating device 16 preferably acquires the electrical parameter directly from the inverter 48.

[0039] Figure 2 shows the method 10 for operating the electrochemical device 12. During a start 50 of the method 10, the electrochemical device 12 is preferably put into operation. During the start 50, the control or regulating device 16 preferably controls an operating point of the electrochemical device 12. The method 10 preferably comprises an operating characteristic determination step 52. In the operating characteristic determination step 52, the control or regulating device 16 determines an operating characteristic based on operating parameters detected by the sensor unit. In the operating characteristic determination step 52 of the method 10, at least one operating parameter and at least one further operating parameter different from the operating parameter are detected for controlling or regulating the electrochemical device 12.Preferably, the sensor unit detects, as one of the operating parameters, the flow parameter, in particular the volume flow, of the reactant fluid, the inlet temperature of the reactant fluid, the outlet temperature of the product fluid, and the electrical parameter of the electrochemical conversion unit 18, in particular an electrical current provided by the electrochemical conversion unit 18 and an electrical voltage associated with the electrical current. Preferably, the control or regulating device 16 and the sensor unit perform the operating parameter determination step 52 continuously.

[0040] Preferably, the method 10 includes a dispersion determination step 54. In the dispersion determination step 54, the control or regulating device 16 evaluates a temporal profile of the operating parameter combining the at least one operating parameter and the at least one further operating parameter. The control or regulating device 16 determines a dispersion measure of the operating parameter. The control or regulating device 16 determines the empirical variance of the operating parameter as the dispersion measure.

[0041] The method 10 preferably comprises a dispersion evaluation step 56. In the dispersion evaluation step 56, the control or regulating device 16 evaluates the degree of dispersion of the operating characteristic in order to detect the achievement of a steady-state operating state 14 of the electrochemical device 12. In the dispersion evaluation step 56, the control or regulating device 16 determines whether a steady-state operating state 14 of the electrochemical device 12 has been reached or whether the electrochemical device 12 is (still) in a transient operating state 58. The control or regulating device 16 preferably determines that the electrochemical device 12 is in the steady-state operating state 14 if the degree of dispersion is less than a predetermined threshold value. The threshold value can be an absolute value or a value relative to a mean value of the operating characteristic.The control or regulating device 16 preferably determines that the electrochemical device 12 is in the transient operating state 58 when the degree of scatter is greater than the predetermined threshold value.

[0042] The method 10 preferably comprises a storage step 60. In the storage step 60, the control or regulating device 16 preferably stores the operating characteristic and preferably the degree of dispersion. In the operating characteristic determination step 52, an exponentially smoothed average of the operating characteristic is determined, and in the dispersion determination step 54, the degree of dispersion of the exponentially smoothed average of the operating characteristic is determined. A smoothing factor for determining the exponentially smoothed average depends on a relaxation time of the electrochemical device 12. The relaxation time, which is determined in particular by a heat capacity of the electrochemical conversion unit 18, can be determined prior to the method 10 and stored in a memory of the control or regulating device 16, or can be determined by the control or regulating device 16 through a test operation of the electrochemical device 12.Preferably, the smoothing factor is dependent, in particular proportional, on a ratio of the relaxation time to the duration of a time window, which defines a number of values ​​of the operating characteristic to be considered when determining the exponentially smoothed average. At least two values ​​of the operating characteristic that are used to decide whether or not the steady-state operating state 14 exists are separated by more than 10 minutes.

[0043] Preferably, the control or regulating device 16 recursively determines the exponentially smoothed average of the operating characteristic and its degree of dispersion depending on the most recently determined value of the operating characteristic, the most recently determined value of the exponentially smoothed average, and the most recently determined value of the degree of dispersion. Preferably, the most recently determined value of the exponentially smoothed average of the operating characteristic is stored in the storage step 60, in particular instead of the most recently determined value of the operating characteristic. Alternatively, a predetermined number of values ​​of the operating characteristic determined within a time window are collected in the storage step 60 in order to determine the degree of dispersion using an explicit form of the degree of dispersion.

[0044] Upon reaching the steady-state operating state 14, the control or regulating device 16 preferably switches from an operating point control to a monitoring mode and / or outputs an indication signal that the electrochemical device 12 is in the steady-state operating state 14. After reaching the steady-state operating state 14, the temporal progression of the operating parameter until reaching the steady-state operating state 14 is evaluated by the control or regulating device 16 or an external computing device to assess the condition of the electrochemical device 12. The condition assessment can be output by the control or regulating device 16, for example, to a maintenance service, and / or further processed to adapt a control or regulating system.

Claims

Claims 1. A method for operating an electrochemical device, in particular a fuel cell device, wherein in at least one method step at least one operating parameter and at least one further operating parameter different from the operating parameter are detected for controlling or regulating the electrochemical device and wherein in at least one method step it is determined that a steady-state operating state (14) of the electrochemical device has been reached, characterized in that a time profile of an operating characteristic, in particular an individual one, summarizing the at least one operating parameter and the at least one further operating parameter is evaluated in order to recognize the reaching of the steady-state operating state (14).

2. Method according to claim 1, characterized in that the operating characteristic combines as operating parameters at least one electrical parameter, one flow parameter and one thermal parameter of the electrochemical device in order to detect the achievement of the steady-state operating state (14).

3. Method according to claim 1 or 2, characterized in that in at least one method step a scatter measure of the operating characteristic is evaluated in order to detect the achievement of the steady-state operating state (14).

4. Method according to claim 3, characterized in that in at least one method step the empirical variance of the operating parameter is used as a measure of dispersion.

5. Method according to one of the preceding claims, characterized in that at least two values ​​of the operating characteristic, which are used in a decision as to whether the stationary operating state (14) exists or not, are more than 10 minutes apart.

6. Method according to one of the preceding claims, characterized in that in at least one method step an exponentially smoothed average of the operating characteristic is determined.

7. Method at least according to claim 5, characterized in that in at least one method step a smoothing factor for determining the exponentially smoothed average is selected depending on a relaxation time of the electrochemical device.

8. Method according to one of the preceding claims, characterized in that in at least one method step the temporal course of the operating parameter until the stationary operating state (14) is reached is evaluated for a condition assessment of the electrochemical device.

9. Control or regulating device for an electrochemical device for carrying out a method according to one of the preceding claims.

10. Electrochemical device, in particular fuel cell device, with at least one electrochemical conversion unit (18) and with at least one control or regulating device according to claim 9.

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