Method for operating an electrochemical device, control or regulating device and electrochemical device

Abstract

The invention relates to a method for operating an electrochemical device, in particular a fuel cell device, 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, in at least one method step, it is determined that a steady-state operating state (14) of the electrochemical device has been reached. According to the invention, a time variation of the at least one operating parameter and the at least one further operating parameter, in particular an individual operating characteristic variable, is evaluated in order to detect the achievement of the steady-state operating state (14).

Description

Background Art

[0001] A method for operating an electrochemical device, in particular a fuel cell device, has been proposed, 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, wherein, in at least one method step, it is determined that a steady-state operating state of the electrochemical device has been reached. Summary of the invention

[0002] The present 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, wherein in at least one method step it is determined that a steady-state operating state of the electrochemical device has been reached.

[0003] It is proposed that the analysis combines the time course of the at least one operating parameter and the at least one further operating parameter, in particular a single operating characteristic variable, in order to identify the reaching of a steady-state operating state. 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, under the supply of oxygen while providing electrical energy. Preferably, the at least one fuel cell converts an oxygen-containing fluid as a reactant fluid into an oxygen-depleted exhaust gas as a product fluid. Preferably, the at least one fuel cell converts a fuel as another reactant fluid into a fuel-depleted exhaust gas as another product fluid. The terms "fuel-depleted" and "oxygen-depleted" refer to the content of fuel or oxygen in the respective product fluid relative to the respective reactant fluid. Alternatively, the electrochemical conversion unit comprises at least one electrolyzer, for example, for decomposing 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.

[0004] As operating parameters and / or as further operating parameters, the sensor unit detects, for example, electrical parameters of the electrochemical conversion unit, thermal parameters of the electrochemical conversion unit, the product fluid and / or the reactant fluid, flow parameters of the product fluid and / or the reactant fluid, etc. Electrical parameters are, for example, the current provided or absorbed by the electrochemical conversion unit and / or the electrical power provided or absorbed by the electrochemical conversion unit and / or the voltage present on the electrochemical conversion unit. Thermal parameters are, for example, the temperature or heat of the reactant fluid when entering the electrochemical conversion unit or the temperature or heat of the product fluid when being discharged from the electrochemical conversion unit. Flow parameters are, for example, the volume flow rate of the product fluid or the reactant fluid, the amount flow rate of the substance, the particle flow rate or the mass flow rate, the pressure or pressure difference in the reactant fluid or the product fluid, etc.

[0005] Preferably, the control or regulating device of the fuel cell device determines the operating characteristic variable according to the operating parameter and according to other operating parameters (especially according to more than two operating parameters). The operating characteristic variable preferably depends on the overall state of the electrochemical device. Particularly preferably, the operating characteristic variable depends 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 characteristic variable is a physical and / or chemical parameter or characteristic value, such as voltage, temperature, energy, etc. Alternatively, the operating characteristic variable is an abstract function without physical and chemical meaning, such as the result of a scoring system. Particularly preferably, the control or regulating device only analyzes the operating characteristic variable, and especially analyzes the processing time when necessary according to the configuration of the method to determine whether the electrochemical device is in a steady state or a non-steady state operating state. Particularly preferably, the control or regulating device identifies the steady state operating state by only not significantly changing the operating characteristic variable. In particular, the control or regulating device identifies non-steady state operation by significantly changing the operating characteristic variable. The control or regulating device preferably determines a significant change and / or an insignificant change of the operating characteristic variable by comparing a change variable that characterizes or describes the time change process of the operating characteristic variable with a threshold value. The change variable can be constructed, for example, as a differential, a differential quotient, a difference between the values ​​of the continuously determined operating characteristic variable, in particular a degree of discreteness, etc. Preferably, the control or regulating device determines a plurality of values ​​of the operating characteristic variable within a time window. Particularly preferably, the control or regulating device continuously determines the value of the operating characteristic variable, in particular at predetermined regular time intervals or in real time. Here, "real time" should be understood as a time interval that is only limited by the data processing speed of the control or regulating device. Alternatively, the control or regulating device limits the determination of the value of the operating characteristic variable to 10 milliseconds, in particular to 50 milliseconds. Particularly preferably, the control or regulating device determines at least one value of the operating characteristic variable within 10 minutes, preferably determines at least one value of the operating characteristic variable per minute, particularly preferably determines at least one value of the operating characteristic variable within 10 seconds, and extremely preferably determines at least one value of the operating characteristic variable per second. The control or regulating device preferably ascertains the changing variable as a function of a plurality of values ​​(preferably a majority of values, in particular all values) of the characteristic operating variable ascertained within the time window. Optionally, the control or regulating device excludes individual values ​​of the characteristic operating variable ascertained within the time window from further processing for the changing variable, for example on the basis of a plausibility check or the like. The control or regulating device preferably ascertains the changing variable as a function of more than three, particularly preferably more than five, particularly preferably more than ten values ​​of the characteristic operating variable ascertained at different points in time, in particular within the time window.

[0006] The control or regulating device is preferably configured to achieve a steady-state operating state by changing operating parameters. In particular, the control or regulating device controls at least one servo unit (Stelleinheit) of the electrochemical device in a non-steady-state operating state or when the operating point is switched to change at least one operating parameter and / or additional, unmonitored operating parameters of the operating parameters of the electrochemical device. The servo unit is, for example, a conveying unit, in particular a pump, a compressor, a blower, etc., for adjusting flow parameters and or thermal parameters. The servo unit is, for example, an inverter or an adjustable resistor, for adjusting electrical parameters. Preferably, the control or regulating device switches to a monitoring and / or analysis mode when a steady-state operating state is reached. The monitoring and / or analysis mode is preferably configured to maintain a steady-state operating state and selectively analyze the actual value of at least one operating parameter in the steady-state operating state for performing an operation analysis of the electrochemical device, such as for analysis of reactant fluids, detection of degradation of electrochemical conversion units, detection of the efficiency of electrochemical devices, etc.

[0007] By the configuration according to the present invention, the steady-state operating state can be advantageously simply identified. In particular, it is possible to save the need to determine a large number of standards, threshold values, time constants, etc. for each individual operating parameter. In addition, the waiting time after the load change to ensure the existence of the steady-state operating state can be kept short. In particular, when the load changes, the stabilization of the steady-state operating state can be targeted. This allows for advantageously robust system dynamics. The method is advantageously robust and at the same time advantageously simple in terms of implementation, and allows for a simple interpretation of the operating characteristic parameters. In addition, it is advantageously possible to reliably implement extended regulation and control functions and soft sensor concepts, which are, for example, based on energy balance and are therefore only effective in the steady-state operating state. In particular, an advantageous and comprehensive analysis possibility for the behavior of the electrochemical device is obtained. In addition, due to the inclusion of combined parameters in monitoring instead of a large number of individual operating parameters, an advantageously high storage and computing efficiency of the control or regulating device can be achieved.

[0008] It is further proposed that the operating characteristic variable as an operating parameter combines at least an electrical parameter, a flow parameter and a thermal parameter of the electrochemical device in order to identify the achievement of a steady-state operating state. Particularly preferably, the control or regulating device (especially without an additional sensor) determines the operating characteristic variable based on standard sensor data of the sensor unit, which is detected for controlling or regulating the electrochemical device. The control or regulating device determines the operating characteristic variable K, for example, based on the following calculation rule:

[0009]

[0010] Among them, I el is the current generated by the electrochemical conversion unit, UZellen is related to the generated current I el The voltage of the electrochemical conversion unit, N Zellen is the number of fuel cells or electrolyzers in the electrochemical conversion unit, where F is the Faraday constant and h aus represents the molar enthalpy of the product fluid when it is discharged from the electrochemical conversion unit, h ein represents the molar enthalpy of the reactant fluid when it enters the electrochemical conversion unit, and represents the mass flow rate of the reactant fluid (Stoffstrom). Electrical parameters (i.e., current I el and voltage U Zellen ) is preferably detected by a sensor unit. The flow parameter (ie the mass flow ) is preferably detected by the sensor unit or is determined from the volume flow or mass flow detected by the sensor unit. Molar enthalpy h aus 、h ein The control or regulation device preferably determines the temperature of the reactant fluid or product fluid as a function of the temperature detected by the sensor unit. Preferably, a memory of the control or regulation device stores a molar enthalpy h that is dependent on the temperature of the reactant fluid or product fluid. aus 、h ein The control or regulation device uses this regression function to obtain the molar enthalpy h aus 、h ein . Preferably, the control or regulating device uses an oxygen-containing fluid as the reactant fluid and an oxygen-depleted exhaust gas as the product fluid to determine the operating characteristic variable. Through the configuration according to the invention, important related operating parameters can be advantageously physically associated for evaluating the operating state of the electrochemical device. In particular, a single physically interpretable variable can be used to monitor the operating state. A standard parameterization that allows the operating state to be inferred from the operating characteristic variable only needs to be created for this one operating characteristic variable rather than for each operating parameter.

[0011] It is further proposed that in at least one method step of the method, the degree of discreteness of the operating characteristic parameter is analyzed to identify the reaching of the steady-state operating state. The control or regulating device preferably analyzes the value of the operating characteristic parameter obtained in the time window to obtain the degree of discreteness. The time window is preferably a sliding time window. The control or regulating device preferably regularly updates the time window, especially using the value of each newly obtained operating characteristic parameter. As the degree of discreteness, for example, the sum of squared deviations, empirical variance, empirical standard deviation, coefficient of variation, average absolute deviation from the mean value, quantile distance, etc. of the values ​​of the operating characteristic parameter obtained in the time window can be used. The mean value of the operating characteristic parameter can represent the arithmetic mean, geometric mean, median or other mean value of the operating characteristic parameter. Preferably, the control or regulating device analyzes the value of the obtained discreteness to determine whether the electrochemical device is in a steady-state operating state or a non-steady-state operating state, especially independently of the mean value of the operating characteristic parameter. Preferably, if the degree of discreteness is less than a threshold value, the control or regulating device determines that the electrochemical device is in a steady-state operating state. The threshold value can be defined absolutely or relative to the mean value. Preferably, if the degree of dispersion is greater than the threshold value or another threshold value different from the threshold value, the control or regulating device determines that the electrochemical device is in a non-steady-state operating state. Alternatively, the control or regulating device analyzes and processes the operating characteristic variable by wavelet transformation to identify the reaching of the steady-state operating state. Through the configuration according to the present invention, the time variation process of the operating characteristic variable can be advantageously simply analyzed and processed.

[0012] It is further proposed that in at least one method step of the method, the empirical variance of the operating characteristic variable is used as the degree of dispersion. The empirical variance can be calculated as the sum of 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). By means of the configuration according to the invention, the temporal variation of the operating characteristic variable can be advantageously and simply analyzed.

[0013] It is further proposed that at least two values ​​of the operating characteristic parameter included in the judgment of whether a steady-state operating state exists are separated by more than 10 minutes. The time window can be defined directly by the duration, especially when the values ​​of the operating characteristic parameter are stored in the form of a time stamp, and / or, by the number of values ​​of the operating characteristic parameter, especially when these values ​​are detected at regular intervals in time. Preferably, the time window includes at least 10 minutes, preferably at least 20 minutes, and particularly preferably at least 30 minutes. Preferably, the control or regulating device stores all the values ​​obtained of the operating characteristic parameter in the time window. Preferably, the control or regulating device stores at most a predetermined maximum number of values ​​of the operating characteristic parameter, which is preferably defined by the time window. When the maximum number of values ​​of the reference characteristic parameter is reached, each newly obtained value of the operating characteristic parameter preferably replaces the stored value of the operating characteristic parameter according to the first-in-first-out (FIFO) principle. Through the configuration according to the present invention, it is preferably possible to reliably evaluate whether the operating state is steady or non-steady.

[0014] It is further proposed that in at least one method step of the method, an exponentially smoothed average value of the operating characteristic parameter is obtained. Preferably, the control or regulation device obtains the average value of the operating characteristic parameter as an exponentially smoothed average value based on all values ​​obtained in the time window. Preferably, the control or regulation device obtains the degree of dispersion based on the exponentially smoothed average value. Preferably, the control or regulation device recursively updates the degree of dispersion. Preferably, the control or regulation device updates the degree of dispersion for each newly obtained value K of the operating characteristic parameter. i Calculate the value of the newly calculated operating characteristic parameter and the previous value K of the exponential smoothing average ema,i-1 The deviation δ i , especially according to:

[0015] δ i =K i –K ema,i-1

[0016] Preferably, the control or regulating device sets the newly determined value K of the operating characteristic variable i The deviation δ i The previous value K added to the exponentially smoothed mean ema,i-1 To update the exponential smoothing mean K ema,i , where the deviation is loaded with a smoothing factor α, in particular according to:

[0017] K ema,i =α·δ i +K ema,i-1

[0018] Preferably, the control or regulation device adjusts the value of the discrete degree var(K) according to the smoothing factor a, the previous value of the discrete degree var(K) ema,i-1 The deviation δ from the value of the newly determined operating characteristic variablei To obtain the updated discrete value var(K) ema,i , especially according to:

[0019]

[0020] The smoothing factor is preferably between 0 and 1. Preferably, the control or regulation device non-recursively determines the initial value var(K) of the degree of discreteness ema,0 , in particular with the aid of an explicit form of the degree of dispersion, such as the sum of squared deviations. As the initial value K of the operating characteristic variable ema,0 The control or regulating device can use the arithmetic mean, the geometric mean, the median of the values ​​of the characteristic operating variable in a time window, specific values ​​of the determined values ​​of the characteristic operating variable (e.g. the first value, the last value, etc.) or randomly selected values ​​of the characteristic operating variable. By means of the embodiment according to the invention, the memory consumption and / or the necessary computing power of the control or regulating device for detecting the steady-state operating state can be kept advantageously low.

[0021] It is further proposed that in at least one method step of the method, a smoothing factor for obtaining an exponentially smoothed average is selected according to the relaxation time of the electrochemical device. The time window is preferably longer than the relaxation time of the electrochemical device. Preferably, the smoothing factor is obtained according to the ratio of the relaxation time to the duration of the time window. The relaxation time of the electrochemical device depends on the thermal capacity of the electrochemical conversion unit and in particular describes how quickly, in particular exponentially, the temperature of the electrochemical conversion unit approaches a new equilibrium temperature when the steady-state operating state is intentionally left or caused to leave the steady-state operating state due to a disturbance. Through the configuration according to the invention, the ratio of the importance of the past value and the current value of the operating characteristic parameter in the exponentially smoothed average can be advantageously associated with the dynamics that are important to the electrochemical device.

[0022] It is further proposed that in at least one method step of the method, the time variation of the operating characteristic variable until the steady-state operating state is reached is analyzed and processed for state evaluation of the electrochemical device. The state evaluation may, for example, include fault analysis, service life prediction and / or determination of the degree of degradation of the electrochemical device by a control or regulating device or an external computing unit. Preferably, the control or regulating device outputs a signal that the steady-state state has been reached when the steady-state state is identified, so that the state evaluation related to the steady-state state can be started by the external computing unit. Additionally or alternatively, the control or regulating device immediately analyzes and processes the time variation of the operating characteristic variable to perform state evaluation. For example, the control or regulating device or the external computing unit obtains the duration until the steady-state operating state is reached, the amplitude of the overshoot or asymptotic creep behavior of the operating characteristic variable, the damping of the amplitude of the overshoot of the operating characteristic variable, the average value of the operating characteristic variable when the steady-state operating state is reached, etc. Alternatively or additionally, the control or regulating device stores and / or sends the time variation of the operating characteristic variable for analysis and processing by a maintenance technician and / or an external computing device, such as a server, on which a machine learning process for state evaluation is implemented. By the configuration according to the invention, advantageously, many additional parameters can be used for the state evaluation. In addition, the start time of the state evaluation can be advantageously selected reliably in the steady-state operating state.

[0023] Furthermore, a control or regulating device for an electrochemical device is proposed for carrying out the method according to the invention. The control or regulating device is configured to control or regulate the electrochemical device. The control or regulating device is preferably a unit having at least one control electronics. "Control electronics" is to be understood in particular as a unit having a processor unit and having a memory and having an operating program stored in the memory. By means of the configuration according to the invention, a control or regulating device can be provided which can reliably identify a steady-state operating state with advantageously low storage and / or computing requirements.

[0024] In addition, an electrochemical device, in particular a fuel cell device, is proposed, which has at least one electrochemical conversion unit and has at least one control or regulation device according to the present invention. The electrochemical conversion unit preferably includes at least one fuel cell or electrolyzer, preferably a stack of (especially structurally identical) fuel cells or electrolyzers or a combination of multiple stacks of (especially structurally identical) fuel cells or electrolyzers. The at least one fuel cell is preferably configured 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 configured as a high-temperature electrolyzer, in particular a solid oxide electrolyzer cell.

[0025] Preferably, the electrochemical device comprises at least one reactant fluid delivery unit or reactant fluid cut-off mechanism for adjusting the inflow rate of fresh reactant fluid to the electrochemical conversion unit. The reactant fluid delivery unit or the reactant fluid cut-off mechanism is preferably controlled by a control or regulating device to adjust the steady-state operating state. The electrochemical device preferably comprises at least one inverter and / or adjustable resistor for adjusting electrical parameters. The inverter and / or adjustable resistor are preferably controlled by a control or regulating device to adjust the steady-state operating state. The electrochemical device preferably comprises a sensor unit for detecting the operating parameters of the electrical device. The sensor unit, for example, comprises at least one temperature sensor located upstream of the electrochemical conversion unit. The sensor unit, for example, comprises at least one additional temperature sensor located downstream of the electrochemical conversion unit and / or in the electrochemical conversion unit or on the electrochemical conversion unit. The sensor unit, for example, comprises an ammeter and / or a voltmeter for detecting electrical parameters. The sensor unit preferably comprises at least one flow meter for detecting flow parameters.

[0026] In particular, when configured as a fuel cell device, the electrochemical device optionally includes an afterburner for utilizing fuel residues in the fuel-lean exhaust gas, a desulfurizer and / or a reformer for pretreating the fuel, a heat exchanger for transferring heat from the product fluid to the reactant fluid and / or a recirculation line for returning the product fluid to the reactant fluid.

[0027] By means of the embodiment according to the invention, an electrochemical device can be provided, the operating state of which can be ascertained advantageously promptly (in particular in real time), advantageously reliably and advantageously in a resource-saving manner during the operation of the electrochemical device.

[0028] 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 to be restricted to the above-mentioned applications and embodiments. 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 may have a number of individual elements, components and units and method steps different from the number mentioned herein to realize the functional mode described herein. In addition, with regard to the value ranges given in the present disclosure, the values ​​within the mentioned limits should also be regarded as disclosed and can be used arbitrarily. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further advantages are apparent from the following description of the drawings. An embodiment of the invention is presented in the drawings. The drawings, the description and the claims contain features in many combinations. A person skilled in the art will expediently consider these features individually and combine them into other meaningful combinations.

[0030] The accompanying drawings show:

[0031] Figure 1A schematic diagram of an electrochemical device according to the present invention; and

[0032] Figure 2 Schematic flow chart of the method according to the invention. DETAILED DESCRIPTION

[0033] Figure 1 An electrochemical device 12 is shown. The electrochemical device 12 is configured as a fuel cell device, for example. The electrochemical device 12 preferably includes at least one electrochemical conversion unit 18. The electrochemical conversion unit 18 includes 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 represented as a single fuel cell here. The electrochemical conversion unit 18, in particular each fuel cell of the electrochemical conversion unit 18, includes at least one oxygen electrode 20 and at least one fuel electrode 22. The oxygen electrode 20 is configured to directly contact an oxygen-containing fluid as a reactant fluid. The oxygen electrode 20 preferably outputs an oxygen-depleted exhaust gas as a product fluid. The fuel electrode 22 is configured to directly contact a fuel as another reactant fluid. The fuel electrode 22 preferably outputs a fuel-depleted exhaust gas as another product fluid. The electrochemical device 12 preferably includes an inverter 48, which is electrically connected to the oxygen electrode 20 and the fuel electrode 22.

[0034] Particularly preferably, the at least one fuel cell, in particular all fuel cells of the electrochemical conversion unit 18 , are designed as solid oxide fuel cells (SOFC).

[0035] The electrochemical device 12 preferably comprises a reactant fluid delivery unit 24, in particular a fan, a blower or a compressor, for delivering the oxygen-containing fluid to the oxygen electrode 20. Particularly preferably, the oxygen-containing fluid is ambient air, which is sucked 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.

[0036] The electrochemical device 12 preferably includes another reactant fluid delivery unit 26, in particular a fan, a blower or a compressor, for delivering fuel to the fuel electrode 22. The fuel is preferably hydrogen and / or natural gas. Alternatively, the fuel includes at least one hydrocarbon as a pure substance or as a mixture and / or ammonia. Another reactant fluid delivery unit 26 is arranged upstream of the fuel electrode 22 with respect to the fuel. In order to provide electrical energy, the electrochemical conversion unit 18 is preferably configured to convert the fuel into another product fluid under the condition of supplying oxygen from the oxygen-containing fluid.

[0037] Optionally, the electrochemical device 12 includes a desulfurizer 28. The desulfurizer 28 is preferably arranged downstream of the other reactant fluid delivery unit 26 and upstream of the electrochemical conversion unit 18 with respect to the other reactant fluid. Optionally, the electrochemical device 12 includes a reformer 30 for reforming the other reactant fluid. The reformer 30 is preferably arranged downstream of the other reactant fluid delivery unit 26 (especially downstream of the desulfurizer 28) and upstream of the electrochemical conversion unit 18 with respect to the other reactant fluid.

[0038] Preferably, the electrochemical device 12 includes a recirculation line 34 and a recirculation transport unit 36 ​​(especially arranged in or on the recirculation line 34), especially a fan, a blower or a compressor, for guiding another product fluid discharged from the fuel electrode 22 back to another reactant fluid upstream of the fuel electrode 22. The feed inlet of the recirculation line 34 is preferably arranged upstream of the reformer 30 and downstream of the desulfurizer 28 with respect to the other reactant fluid.

[0039] The electrochemical device 12 preferably includes an afterburner 32 for converting the fuel residue contained in another product fluid. The afterburner 32 is preferably arranged downstream of the fuel electrode 22 with respect to another product fluid, and in particular downstream of the branch of the recirculation line 34. The afterburner 32 is preferably arranged downstream of the oxygen electrode 20 with respect to the product fluid. Preferably, the electrochemical device 12 includes a heat exchanger 38 for transferring the heat of the afterburner exhaust gas of the afterburner 32 discharged 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 delivery unit 24 and upstream of the electrochemical conversion unit 18 with respect to the reactant fluid. Preferably, the electrochemical device 12 includes another heat exchanger 40 for transferring the heat of the afterburner exhaust gas of the afterburner 32 discharged from the afterburner 32 to another reactant fluid upstream of the electrochemical conversion unit 18. Another heat exchanger 40 is preferably arranged downstream of the desulfurizer 28 with respect to the other reactant fluid and upstream of the feed inlet of the recirculation line 34. Here, the other heat exchanger 40 is arranged, by way of example, downstream of the heat exchanger 38 with respect to the afterburner exhaust gas. Alternatively, the heat exchanger 38 is arranged downstream of the other heat exchanger 40 with respect to the afterburner exhaust gas.

[0040] The electrochemical device 12 includes at least one control or regulating device 16. The control or regulating device 16 is preferably configured to control the reactant fluid delivery unit 24, the other reactant fluid delivery unit 26, and the recirculation delivery unit 36 ​​to adjust the flow parameters of the reactant fluid and / or the other reactant fluid through the electrochemical conversion unit 18. The control or regulating device 16 is preferably configured to control the inverter 48 to adjust the electrical parameters of the electrochemical conversion unit 18. The control or regulating device 16 is configured to perform the method 10, which will be described below. Figure 2 Explained in detail.

[0041] The electrochemical device 12 includes at least one sensor unit. The sensor unit preferably includes a flow meter 42 for detecting the flow parameters of the reactant fluid. The flow meter 42 is preferably arranged downstream of the reactant fluid delivery unit 24 and upstream of the electrochemical conversion unit 18, especially upstream of the heat exchanger 38. Alternatively, the control or regulation device 16 obtains the flow parameters from the delivery power (especially the rotation speed) of the reactant fluid delivery unit 24. The sensor unit preferably includes at least one inlet temperature sensor 44 for detecting the inlet temperature of the reactant fluid when entering 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 delivery unit 24, especially downstream of the heat exchanger 38. The sensor unit preferably includes at least one outlet temperature sensor 46 for detecting the outlet temperature of the product fluid when it is discharged from 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 regulation device 16 preferably obtains the electrical parameters directly from the inverter 48.

[0042] Figure 2 A method 10 for operating an electrochemical device 12 is shown. When the method 10 is started 50, the electrochemical device 12 is preferably put into operation. During the start-up 50, the control or regulating device 16 preferably controls the operating point of the electrochemical device 12. The method 10 preferably includes an operation characteristic variable determination step 52. In the operation characteristic variable determination step 52, the control or regulating device 16 determines the operation characteristic variable based on the operating parameter detected by the sensor unit. In the operation characteristic variable determination step 52 of the method 10, at least one operating parameter and at least one other operating parameter different from the operating parameter are detected for controlling or regulating the electrochemical device 12. Preferably, the sensor unit detects a flow parameter of the reactant fluid (especially a volume flow), an inlet temperature of the reactant fluid, an outlet temperature of the product fluid and an electrical parameter of the electrochemical conversion unit 18 (especially a current provided by the electrochemical conversion unit 18 and a voltage related to the current) as one of the operating parameters. Preferably, the control or regulating device 16 and the sensor unit continuously perform the operation characteristic variable determination step 52.

[0043] Preferably, the method 10 includes a discrete determination step 54. In the discrete determination step 54, the control or regulating device 16 analyzes the time variation of the operating characteristic variable that combines the at least one operating parameter and the at least one other operating parameter. The control or regulating device 16 determines the degree of discreteness of the operating characteristic variable. The control or regulating device 16 determines the empirical variance of the operating characteristic variable as the degree of discreteness.

[0044] Preferably, the method 10 includes a discrete evaluation step 56. In the discrete evaluation step 56, the control or regulating device 16 analyzes the degree of discreteness of the operating characteristic variable in order to identify the reaching of the steady-state operating state 14 of the electrochemical device 12. In the discrete evaluation step 56, the control or regulating device 16 determines whether the steady-state operating state 14 of the electrochemical device 12 has been reached or whether the electrochemical device 12 is (still) in a non-steady-state operating state 58. Preferably, if the degree of discreteness is less than a predetermined threshold value, the control or regulating device 16 determines that the electrochemical device 12 is in a steady-state operating state 14. The threshold value can be an absolute value or a value relative to the average value of the operating characteristic variable. Preferably, if the degree of discreteness is greater than a predetermined threshold value, the control or regulating device 16 determines that the electrochemical device 12 is in a non-steady-state operating state 58.

[0045] 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 variable and preferably stores the degree of dispersion. In the operating characteristic variable determination step 52, an exponentially smoothed average value of the operating characteristic variable is determined, and in the discrete determination step 54, the degree of dispersion of the exponentially smoothed average value of the operating characteristic variable is determined. The smoothing factor for determining the exponentially smoothed average value depends on the relaxation time of the electrochemical device 12. The relaxation time, which is given in particular by the heat capacity of the electrochemical conversion unit 18, can be determined in the preparation phase (Vorfeld) of the method 10 and stored in the memory of the control or regulating device 16, or can be determined by the control or regulating device 16 through a test run of the electrochemical device 12. Preferably, the smoothing factor depends on the ratio of the relaxation time to the duration of the time window, in particular, is proportional to the ratio of the relaxation time to the duration of the time window, which determines the number of values ​​of the operating characteristic variable to be considered when determining the exponentially smoothed average value. At least two values ​​of the operating characteristic variable that are included in the determination of whether a steady-state operating state 14 exists are separated by more than 10 minutes.

[0046] Preferably, the control or regulating device 16 recursively determines the exponentially smoothed mean value of the operating characteristic variable and its degree of dispersion as a function of the value of the last determined operating characteristic variable, the value of the last determined exponentially smoothed mean value and the value of the last determined degree of dispersion. Preferably, the value of the last determined exponentially smoothed mean value of the operating characteristic variable is stored in the storage step 60, in particular instead of the value of the last determined operating characteristic variable. Alternatively, a predetermined number of values ​​of the determined operating characteristic variable (in particular all in the time window) are collected in the storage step 60 in order to determine the degree of dispersion by means of an explicit form of the degree of dispersion.

[0047] When the steady-state operating state 14 is reached, the control or regulating device 16 preferably switches from the operating point control to the monitoring mode and / or outputs a warning signal that the electrochemical device 12 is in the steady-state operating state 14. After reaching the steady-state operating state 14, the time course of the operating characteristic variable until the steady-state operating state 14 is reached is analyzed by the control or regulating device 16 or an external computing device for the state evaluation of the electrochemical device 12. The state evaluation can be output by the control or regulating device 16 (for example, to a maintenance service) and / or further processed to adjust the control or regulation.

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, 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 an analysis combines the time course of the at least one operating parameter and the at least one further operating parameter, in particular a single operating characteristic variable, in order to identify the reaching of the steady-state operating state (14).

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

3. The method according to claim 1 or 2, characterized in that: In at least one method step, the degree of dispersion of the characteristic operating variable is evaluated in order to detect the reaching of the steady-state operating state (14).

4. The method according to claim 3, characterized in that In at least one method step, an empirical variance of the operating characteristic variable is used as the degree of dispersion.

5. The method according to any one of the preceding claims, characterized in that At least two values ​​of the operating characteristic variable included in determining whether the steady-state operating state (14) exists are separated by more than 10 minutes.

6. The method according to any one of the preceding claims, characterized in that In at least one method step, an exponentially smoothed mean value of the operating characteristic variable is ascertained.

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

8. The method according to any one of the preceding claims, characterized in that In at least one method step, the time course of the characteristic operating variable until the steady-state operating state (14) is evaluated for the purpose of evaluating the state of the electrochemical device.

9. A control or regulating device for an electrochemical device for carrying out the method according to any of the preceding claims.

10. An electrochemical device, in particular a fuel cell device, comprising at least one electrochemical conversion unit (18) and at least one open-loop or closed-loop control device according to claim 9.

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