Method for operating a fuel cell system

Abstract

Method for operating a fuel cell system (100), comprising: - Measuring (110) a current (I) generated by a fuel cell system (100) using a current sensor (10). - Measuring (120) by means of a pressure sensor (20) of a total pressure (p_ges) at a cathode output (51) of a cathode (50) of the fuel cell system (100), - Measuring (130), by means of an air mass flow sensor (30), of an air mass flow (m_dot) entering the cathode (50), - Measuring (140), by means of a temperature sensor (40), a temperature (T) of a coolant which is set up to cool the fuel cell system (100), - Calculate (150), by means of a model which is stored in a control unit (FCCU) of the fuel cell system (100), an oxygen partial pressure (p_O2) at the cathode output (51) as a function of the current (I), the total pressure (p_ges), the air mass flow rate (m_dot) and the temperature (T), and / or - Operation (160) of the fuel cell system (100) by the control unit (FCCU) depending on the calculated oxygen partial pressure (p_O2). Furthermore, the invention relates to a fuel cell system, a computer program product, a computer-readable data carrier, a control unit (FCCU) and a system (200).

Description

[0001] The invention relates to a method with the features of the independent method claim, a fuel cell system with the features of the independent patent claim relating to a fuel cell system, a computer program product with the features of the independent patent claim relating to a computer program product, a computer-readable data carrier with the features of the independent patent claim relating to a computer-readable data carrier, a control unit with the features of the independent patent claim relating to a control unit, and a system with the features of the independent patent claim relating to a system.

[0002] Fuel cell systems are known to be used in systems such as (motor) vehicles to provide (electrical) power. For this purpose, hydrogen and oxygen (especially from the ambient air) can be reacted, thereby generating heat and / or electricity. A control unit may be included, which is designed to operate, in particular to control and / or regulate, the fuel cell system.

[0003] The current state of the art has some drawbacks. For example, the oxygen partial pressure, which is particularly pronounced at the cathode outlet, may not be taken into account during the operation of the fuel cell system. Consequently, the operation of the fuel cell system may be inadequate and / or inaccurate. This can also reduce safety and / or increase wear. A sufficiently high oxygen partial pressure can ensure that there is no reactant depletion and, in particular, the resulting aging (or wear). At the same time, an unnecessarily high oxygen partial pressure can be detrimental, as the increased compressor power can reduce system efficiency.

[0004] Accordingly, an improved procedure will be provided.

[0005] Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the fuel cell system according to the invention, and / or in connection with the computer program product according to the invention, and / or in connection with the computer-readable data carrier according to the invention, and / or in connection with the control unit according to the invention, and / or in connection with the system according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always refers to each other. In particular, advantages described within the scope of the first, second, third, fourth, fifth, and / or sixth aspects also apply to the first, second, third, fourth, fifth, and / or sixth aspects.

[0006] The above problem is solved according to a first aspect by a method for operating a fuel cell system, wherein at least two, in particular three, preferably four (or all) of the following steps are carried out: - Determine, in particular by means of a current sensor, a current generated by a fuel cell system, - Determining, in particular by means of a pressure sensor, a total pressure at a cathode output of a cathode of the fuel cell system, - Determine, in particular by means of an air mass flow sensor, an air mass flow entering the cathode, and / or - Determine, in particular by means of a temperature sensor, the temperature of a coolant which is set up to cool the fuel cell system, - the procedure exhibits: - Calculate, using a model stored in a control unit of the fuel cell system, an oxygen partial pressure at the cathode output as a function of the current, the total pressure, the air mass flow, and the temperature, and - Operation, by the control unit, of the fuel cell system depending on the calculated oxygen partial pressure.

[0007] The method can be (at least partially) computer-implemented. Operation can include, in particular, control and / or regulation, preferably using a control unit (see below). The described steps of the method can be performed in the sequence shown and, in particular, repeatedly. Preferably, the method can be used to operate a fuel cell system according to the second aspect, in particular to control and / or regulate it. A control unit according to the fifth aspect can be used particularly preferably. The control unit can perform the corresponding steps and / or initiate the actions, preferably to implement or initialize them. It can be provided that the steps, in particular the calculation and / or operation, are performed by the control unit, preferably in a discrete time manner and / or according to the system's parameters.for discrete time points, e.g. every 10 ms, in which and / or by the control unit are performed.

[0008] At least one, two, three, or four of the following steps can be performed: - Determining (preferably measuring), in particular by means of a (for this purpose) current sensor, a current generated by a fuel cell system, - Determining (preferably measuring), in particular by means of a (for this purpose) pressure sensor, a total pressure (of the products or the mixture) at a cathode output of a cathode of the fuel cell system, - Determining (preferably measuring), in particular by means of an (appropriately designed) air mass flow sensor, an air mass flow entering the cathode, and / or - Determine (preferably measure), in particular by means of a (for this purpose) temperature sensor, the temperature of a coolant which is set up to cool the fuel cell system.

[0009] It may be provided that, following the (respective) determination and / or measurement, the (determined / measured) current, total pressure, air mass flow and / or temperature is transmitted to the control unit, in particular via a (respective) data connection between sensor and control unit.

[0010] The electricity can be generated by the fuel cell system, in particular by a fuel cell unit of the fuel cell system.

[0011] The air mass flow can preferably be generated by an air blower, which is particularly designed to draw in ambient air, e.g. containing oxygen and / or ambient humidity, and / or to supply it to the cathode.

[0012] The total pressure can preferably be specific to the mixture and / or the products that leave the cathode via the cathode outlet (at the cathode outlet).

[0013] The temperature can be specific to a coolant which, for example via a coolant circuit, provides cooling for the fuel cell system, in particular the fuel cell unit.

[0014] The calculation of the oxygen partial pressure at the cathode output, using a model stored in a control unit of the fuel cell system, can be performed depending on the current, total pressure, air mass flow, and / or temperature, particularly depending on which of these parameters have been determined. These parameters can be measured (by appropriate sensors). Alternatively, the parameters can be (at least partially) estimated and / or calculated from other quantities (or parameters).

[0015] Operating the system while taking the oxygen partial pressure into account can at least partially prevent reactant depletion. It can also reduce wear. Furthermore, it can prevent excessively high oxygen partial pressures, which in particular can prevent excessive compressor power consumption and / or low system efficiency.

[0016] Within the scope of the invention, it can be advantageous that the calculation is carried out depending on the ambient humidity, wherein in particular the ambient humidity is determined by a determination or measurement by an (appropriately equipped) ambient humidity sensor (which is, for example, arranged outside of and / or on the fuel cell system).

[0017] It may be provided that the ambient humidity is determined in the control unit and / or transmitted to the control unit and / or that an estimated value is used by the control unit.

[0018] Within the scope of the invention, it is conceivable that the calculation is carried out depending on the position of an exhaust gas recirculation valve, wherein in particular the position of an exhaust gas recirculation valve is set by the control unit and / or transmitted to it.

[0019] The position of the exhaust gas recirculation (EGR) valve can be determined by a sensor, particularly by the control unit. Alternatively, the control unit can set the position of the EGR valve, for example, by sending a control signal to an actuator of the EGR valve and / or the EGR valve itself. In this case, the control unit can determine the position of the EGR valve based on the control signal (essentially by assumption). The position of the EGR valve can also be used to set an EGR rate. This allows products from the cathode outlet to be (at least partially) reintroduced into the cathode. For example, the cathode outlet can be connected to the cathode inlet, particularly the air blower inlet, via the EGR valve (and corresponding lines).

[0020] Within the scope of the invention, it may be provided that the model comprises a physical model, a data-based model and / or a characteristic curve field-based model, which is determined in particular during commissioning.

[0021] The model can be implemented once for a specific type of fuel cell system. Alternatively, a specific model can be determined for each fuel cell system, particularly during commissioning. It is especially preferred that the oxygen partial pressure is not measured during (subsequent) operation of the fuel cell system. This advantageously eliminates the need for a partial pressure sensor (preferably a mass spectrometer and / or a lambda probe), particularly at the cathode output. This optimizes robustness, wear, and / or costs. It is also preferable that a model be provided, particularly during commissioning, which can then be used (later during operation) to determine the oxygen partial pressure as a function of the current, total pressure, air mass flow, and / or temperature.to calculate). Preferably, a partial pressure sensor, particularly at the cathode output, can be provided when determining the model. This sensor is preferably configured to measure the oxygen partial pressure, especially as a function of a (set) operating point (see below). The model can then be created based on this measurement. After determining the model and / or commissioning, the partial pressure sensor can be removed.

[0022] It may be necessary to provide a physical model of the fuel cell system. This model may consist (primarily or exclusively) of algebraic equations and / or systems of equations, enabling a (preferably) accurate calculation of the oxygen partial pressure, particularly including tolerances and / or errors. For example, a model can be determined based on the following equations, especially during commissioning.

[0023] For the oxygen partial pressure p O2 The following can be true and / or calculable at the cathode output (equation 1): pO2=xO2(λcath−1)(1+ψ)λcath+xO2pges

[0024] The total pressure p can be ges , the oxygen molar fraction in the supplied air x O2 (approximately 21%), the cathode stoichiometry λ cach and / or the Ψ function can be used.

[0025] The function Ψ can be and / or computable (equation 2): ψ=pH2Opin−pH2O

[0026] The partial pressure of water vapor p can be determined in this context. H2O and / or the total pressure p ges be used.

[0027] Furthermore, for cathode stoichiometry λ cach valid and / or calculable (equation 3): λcath=wO2∗m˙inI4Fncells

[0028] The mass fraction of oxygen in the supplied air can be w O2 , the current I, the Faraday constant F, the air mass flow ṁ inand / or the number of (fuel) cells of the fuel cell system or fuel cell stack can be used. By substituting equation 2 and / or 3 into equation 1, the oxygen partial pressure can be calculated and / or estimated accordingly. The aforementioned parameters or quantities can be measured, in particular, by sensors (during commissioning and / or operation).

[0029] Alternatively or additionally, a data-driven model can be provided. Machine learning algorithms can be used to determine the relationships between the parameters and the partial pressure of oxygen, particularly during a training process. Specifically, the relationships between flow rate, total pressure, air mass flow rate, and / or temperature, and the partial pressure of oxygen can be determined. During the training of a model by the control unit, based on the partial pressure of oxygen, flow rate, total pressure, air mass flow rate, and temperature, where the model is configured to calculate a specific partial pressure of oxygen based on these parameters, further parameters (see above) can also be considered.The following data can be used (see below), in particular ambient humidity, the position of the exhaust gas recirculation valve, the (on) position of the hydrogen pressure regulator, the (on) position of the air blower (e.g., speed), the (on) position of the exhaust valve, ambient pressure, and / or ambient temperature, and the like. Additional information, especially when determining the model and / or when calculating the oxygen partial pressure (during operation), can improve the accuracy of the model and / or the determination of the oxygen partial pressure. Using less information can improve the speed of determination and / or still enable (overall) improved operation (e.g., if system components and / or sensors should fail). The data-driven model can be trained using machine learning methods and / or algorithms.For example, a NARX (EN, Nonlinear autoregressive exogenous model), in particular with a Gaussian process (for modeling uncertainties) or a neural network F, can be used. A NARX can provide a data-driven model for determining the oxygen partial pressure (y as the variable of interest in the following equation), in particular: yt=F(yt−1, yt−2, yt−3,…, ut−1, ut−2, ut−3,…)+εt

[0030] The index t is specific for different and / or consecutive time series terms. Therefore, known values ​​y for the oxygen partial pressure (from calibration and / or commissioning) can be used to calculate an oxygen partial pressure (during operation). Furthermore, at least one (or more) current and / or past measured values ​​(from commissioning) for the parameters u (mentioned above) can be used, in particular flow rate, total pressure, air mass flow rate, and / or temperature. Here, ε t An error term that specifically includes uncertainty due to other influences and / or inaccuracies. Therefore, current values ​​y tThe oxygen partial pressure (for oxygen) is determined based on measured and / or past values ​​for the (measured) oxygen partial pressure (during commissioning) and / or measured and / or past values ​​for the (measured) parameter(s), in particular flow rate, total pressure, air mass flow rate, and / or temperature. A gradient descent algorithm or a Levenberg-Marquardt algorithm, especially as the objective function, can be used for training.

[0031] For example, such a model can be implemented in MATLAB. Preferably, in addition to an input layer and / or output layer, 10 hidden layers can be used. The feedback mechanism can be configured as closed, open, or non-existent (disabled). Alternatively or additionally, an NX network, specifically a NARX without output feedback, can be used. Alternatively or additionally, a recurrent neural network (RNN), specifically an LSTM (long short-term memory) and / or GRU (gated recurrent unit), can also be used.

[0032] Alternatively or additionally, a characteristic curve-based model can be provided. Accordingly, a (multidimensional) characteristic curve field can be determined during commissioning or model generation, whereby a corresponding oxygen partial pressure is measured by the partial pressure sensor depending on the respective and / or separate operating points.

[0033] A combination of models can also be used, with the control unit selecting a model and / or a combination of models, particularly during subsequent operation, based on determined and / or known data, especially its reliability. This allows for optimization of accuracy, safety, and / or efficiency.

[0034] It is also conceivable that the model is determined by: - Setting, via the control unit, a multitude of operating points, - Determining, in particular by means of a partial pressure sensor, for example a mass spectrometer and / or a lambda probe, a plurality of oxygen partial pressures, wherein each oxygen partial pressure of the plurality of oxygen partial pressures is specific for one operating point of the plurality of operating points, - Determining, by the control unit, the model depending on the multitude of oxygen partial pressures and the multitude of operating points and / or - Saving the model in the control unit.

[0035] This can be performed repeatedly, particularly during commissioning. Each operating point can have a parameter or values ​​for the valves and / or actuators of the fuel cell system. For example, a large number of different operating points can be cycled through step by step. The numerous operating points (target and / or actual parameter values) and / or (measured and / or actual) oxygen partial pressures can be stored in the control unit and / or used as a basis for determining the model.

[0036] It is also conceivable that when setting a large number of operating points, each operating point includes: - Setting a target current, the investigation includes: - Determining, in particular by means of a current sensor, an actual current, which results in particular depending on the target current and / or the (set) operating point, where the determination is carried out depending on the actual current.

[0037] Within the scope of the invention, it is optionally possible that, particularly when setting a large number of operating points, each operating point includes: - Setting a target total pressure, in particular via an exhaust valve which is controlled by the control unit, the investigation includes: - Determining, in particular by means of the pressure sensor, an actual total pressure, which depends in particular on the target total pressure. and / or the (set) operating point results in, the determination is carried out depending on the actual total pressure.

[0038] Adjusting the settings can be optional, especially since the overall pressure can also be achieved by adjusting other parameters or an operating point. The exhaust valve can be controlled by the control unit, for example, via a data connection through which the control unit transmits a control signal or positioning signal to the exhaust valve (or an actuator of the exhaust valve).

[0039] Furthermore, it may be provided within the scope of the invention that when setting a plurality of operating points, each operating point comprises: - Setting a target air mass flow, in particular via an air blower which is controlled by the control unit, the investigation includes: - Determining, in particular by means of the air mass flow sensor, an actual air mass flow, which results in particular depending on the target air mass flow and / or the (set) operating point, the determination is carried out depending on the actual air mass flow.

[0040] The air blower can be controlled by the control unit, e.g. via a data connection, through which the control unit transmits a control signal or positioning signal to the air blower (or an actuator of the air blower).

[0041] With regard to the present invention, it is conceivable that when setting a plurality of operating points, each operating point comprises: - Setting a target temperature for the coolant used to cool the fuel cell system, the investigation includes: - Determining, in particular by means of the temperature sensor, an actual temperature, which is particularly dependent on the target temperature, the determination is carried out depending on the current temperature.

[0042] Setting the temperature can be optional, especially since the actual temperature can also be determined by adjusting other parameters or an operating point. The coolant system (which is designed for circulation and / or cooling by the coolant) can be controlled by the control unit, for example, via a data connection through which the control unit transmits a control signal or positioning signal to the coolant system (or an actuator, such as a pump, within the coolant system).

[0043] Furthermore, it is conceivable that when setting a large number of operating points, each operating point includes: - Setting a target position of an exhaust gas recirculation valve, the investigation includes: - Determining, in particular by the control unit, the actual position of the exhaust gas recirculation valve, the determination is carried out depending on the actual position of the exhaust gas recirculation valve.

[0044] The exhaust gas recirculation valve can be controlled by the control unit, e.g. via a data connection, through which the control unit transmits a control signal or actuation signal to the exhaust gas recirculation valve (or an actuator of the exhaust gas recirculation valve).

[0045] The above problem is solved according to a second aspect by a fuel cell system according to the invention, comprising a control unit which is configured to implement the method according to the first aspect.

[0046] The fuel cell system can have at least one of the following features: - a current sensor designed to measure a current generated by the fuel cell system, - a pressure sensor configured to measure total pressure at a cathode output of a cathode of the fuel cell system, - an air mass flow sensor configured to measure an air mass flow entering the cathode, and / or - a temperature sensor designed to measure the temperature of a coolant used to cool the fuel cell system.

[0047] This results in the same advantages with regard to a fuel cell system according to the second aspect as have already been described with regard to a method according to the first aspect.

[0048] The above problem is solved according to a third aspect by a computer program product according to the invention, comprising instructions which, when the computer program product is executed by a computer, cause it to implement the method according to the first aspect.

[0049] This results in the same advantages with regard to a computer program product according to the invention as have already been described with regard to a method according to the first aspect and / or a fuel cell system according to the second aspect.

[0050] The above problem is further solved according to a fourth aspect by a computer-readable data carrier according to the invention, in which instructions are stored which, when executed by a computer, cause it to carry out the method according to the first aspect.

[0051] This results in the same advantages with regard to a computer-readable data carrier according to the invention as have already been described with regard to a method according to the first aspect and / or a fuel cell system according to the second aspect and / or a computer program product according to the third aspect.

[0052] The above problem is further solved according to a fifth aspect by a control unit according to the invention, comprising a computing unit and a storage unit in which instructions are stored which, when at least partially executed by the computing unit, perform a method according to the first aspect.

[0053] The control unit, particularly the processing unit, may be configured to execute and / or initiate the process steps, for example, by controlling the fuel cell system and / or its (above-mentioned) components and / or sensors. The control unit can send control signals to corresponding actuators of the fuel cell system to adjust them. The control unit can also receive sensor signals from sensors of the fuel cell system, such as temperature sensors, which are taken into account in the process, particularly during control and / or regulation. Based on this, for example, a current temperature can be determined.

[0054] This results in the same advantages with regard to a control unit according to the invention as have already been described with regard to a method according to the first aspect and / or a fuel cell system according to the second aspect and / or a computer program product according to the third aspect and / or a computer-readable data carrier according to the fourth aspect.

[0055] The above problem is further solved according to a sixth aspect by a system according to the invention comprising a fuel cell system according to the second aspect and / or a control unit according to the fifth aspect.

[0056] A system can comprise a (residential) building, industrial building, power plant, storage facility, vehicle, shipbuilding structure, aircraft, or other system with, in particular, increased energy demand. It may be especially preferred to provide for a (essentially) stationary (immobile) application of the fuel cell system.

[0057] This results in the same advantages with regard to a system according to the invention as have already been described with regard to a method according to the first aspect and / or a fuel cell system according to the second aspect and / or a computer program product according to the third aspect and / or a computer-readable data carrier according to the fourth aspect and / or a control unit according to the fifth aspect.

[0058] Further advantages, features, and details of the invention will become apparent from the following description, in which several exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination. The drawings illustrate this by way of example. Fig. 1 a procedure, Fig. 2 a fuel cell system and Fig. 3 a system.

[0059] The figures use identical reference numerals for the same technical features, even for different embodiments.

[0060] Fig. Figure 1 shows a method for operating a fuel cell system 100, wherein at least two of the following steps are performed: - Determine 110, in particular by means of a current sensor 10, a current I generated by a fuel cell system 100, - Determine, in particular by means of a pressure sensor 20, a total pressure p_ges at a cathode output 51 of a cathode 50 of the fuel cell system 100, - Determine 130, in particular by means of an air mass flow sensor 30, an air mass flow m_dot entering the cathode 50, and / or - Determine, in particular by means of a temperature sensor 40, a temperature T of a coolant which is set up to cool the fuel cell system 100, - the procedure exhibits: - Calculate 150, by means of a model which is stored in a control unit FCCU of the fuel cell system 100, an oxygen partial pressure p_O2 at the cathode output 51 as a function of the current I, the total pressure p_ges, the air mass flow m_dot and the temperature T, and - Operation 160, by the control unit FCCU, of the fuel cell system 100 depending on the calculated oxygen partial pressure p_O2.

[0061] Within the scope of the invention, it can be advantageous that the calculation 150 is carried out depending on an ambient humidity, wherein in particular the ambient humidity is determined by measurement by an ambient humidity sensor.

[0062] Within the scope of the invention, it is conceivable that the calculation 150 is carried out depending on a position of an exhaust gas recirculation valve 60, wherein in particular the position of an exhaust gas recirculation valve 60 is set by the control unit FCCU and / or transmitted to it.

[0063] Within the scope of the invention, it may be provided that the model comprises a physical model, a data-based model and / or a characteristic curve field-based model, which is determined in particular during commissioning.

[0064] It is also conceivable that the model is determined by: - Setting 105, via the FCCU control unit, a multitude of operating points, - Determine 106, in particular by means of a partial pressure sensor 70, for example a mass spectrometer and / or a lambda probe, a plurality of oxygen partial pressures, wherein each oxygen partial pressure of the plurality of oxygen partial pressures is specific for an operating point of the plurality of operating points, - Determine 107, by the FCCU control unit, of the model depending on the multitude of oxygen partial pressures and the multitude of operating points and / or - Save 108 of the model in the FCCU control unit.

[0065] It is also conceivable that when setting 105, a large number of operating points are included, each operating point encompasses: - Setting a target current, where the determination includes 106: - Determine, in particular by means of a current sensor 10, an actual current, which results in particular depending on the target current, where the determination 107 is carried out depending on the actual current.

[0066] Within the scope of the invention, it is optionally possible that, particularly when setting 105 a plurality of operating points, each operating point comprises: - Setting a target total pressure, in particular via an exhaust valve 55, which is controlled by the FCCU control unit, where the determination includes 106: - Determine, in particular by means of the pressure sensor 20, an actual total pressure, which results in particular depending on the target total pressure, where the determination 107 is carried out depending on the actual total pressure.

[0067] Furthermore, it may be provided within the scope of the invention that when setting 105 a plurality of operating points, each operating point comprises: - Setting a target air mass flow, in particular via an air blower 31, which is controlled by the FCCU control unit, where the determination includes 106: - Determine, in particular by means of the air mass flow sensor 30, an actual air mass flow, which results in particular depending on the target air mass flow, where the determination 107 is carried out depending on the actual air mass flow.

[0068] With regard to the present invention, it is conceivable that when setting 105 a plurality of operating points, each operating point comprises: - Setting a target temperature for the coolant used to cool the fuel cell system, where the determination includes 106: - Determine, in particular by means of the temperature sensor 40, an actual temperature, which results in particular depending on the target temperature, where the determination 107 is carried out depending on the actual temperature.

[0069] Furthermore, it is conceivable that when setting 105 a large number of operating points, each operating point includes: - Setting a target position of an exhaust gas recirculation valve 60, where the determination includes 106: - Determine, in particular by the FCCU control unit, the actual position of the exhaust gas recirculation valve 60, where the determination 107 is carried out depending on the actual position of the exhaust gas recirculation valve 60.

[0070] Fig. Figure 2 shows a fuel cell system 100 comprising a control unit FCCU, a computing unit CU and a storage unit MU, in which instructions are stored which, when at least partially executed by the computing unit CU, perform a procedure according to the first aspect and / or Fig. 1. Hydrogen can be introduced via a hydrogen tank 1. The amount of hydrogen and / or a hydrogen mass flow rate can be set via a hydrogen pressure regulator 2, which is fed, in particular, into a fuel cell unit 101 (or a fuel cell stack) of the fuel cell system 100. The control unit FCCU can transmit a control signal to the hydrogen pressure regulator, preferably via a data connection (shown with a dashed line), depending on which a hydrogen mass flow rate is set. In addition, air can be introduced into the fuel cell system 100 (see below the hydrogen tank 1), which in particular has a proportion of oxygen (e.g., ~21%). An air mass flow rate m_dot can be set by an air blower 31.For this purpose, the air blower 31 can receive a control signal from the control unit FCCU, in particular via a data connection (shown with dashed lines). An air mass flow sensor 30 can be provided, which is arranged in particular in front of or behind the air blower 31. The air mass flow sensor 30 can be configured to determine 130, in particular to measure, the air mass flow m_dot. The air mass flow sensor 30 can transmit the air mass flow m_dot (or a corresponding measured value) to the control unit FCCU, in particular via a data connection (shown with dashed lines). In addition, a heat exchanger 32 can be provided, which can advantageously improve the efficiency. The air mass flow m_dot can be fed into the cathode 50, in particular of the fuel cell unit 101. The fuel cell unit 101 (orThe fuel cell stack can have an electrolyte (indicated only above the cathode 50) and an anode arranged above it for supplying hydrogen. Hydrogen and oxygen (from the air) can react within the fuel cell unit 101. This can, in particular, provide a current I. The products of the reaction can be (partially) discharged within the fuel cell unit 101 via a cathode output 51 of the cathode 50. In particular, oxygen can be discharged from the cathode output 51. An oxygen partial pressure p_O2 can be present, especially at and / or near the cathode output 51. The oxygen partial pressure p_O2 can be measured at and / or in the cathode output 51 by a partial pressure sensor 70, in particular a mass spectrometer and / or a lambda probe, especially during commissioning and / or when providing or generating the model.In a (later) operation of the fuel cell system 100, it is preferably provided that the oxygen partial pressure p_O2 is not determined by a partial pressure sensor 70, particularly since this is no longer provided (removed). The oxygen partial pressure p_O2 can then be determined via a model as a function of the current I, the total pressure p_ges, the air mass flow m_dot, and / or the temperature T. The temperature T can be specific to a coolant that cools, in particular, the fuel cell system 100, especially the fuel cell unit 101, and / or the electrolyte (exemplarily represented by a cooling circuit). A temperature sensor 40 can be provided, which is configured for determining 140, in particular measuring, the temperature T and / or is arranged in or on the coolant circuit (preferably outside the fuel cell unit 101).The temperature sensor 40 can be connected to the control unit FCCU, in particular via a data connection (shown with dashed lines), especially to transmit the temperature T to it. A current sensor 10 can be provided, which is configured for determining 110, in particular measuring, the current I generated by the fuel cell system 100. The current sensor 10 can also be connected to the control unit FCCU, in particular via a data connection (shown with dashed lines), especially to transmit the current I to it. A pressure sensor 20 can be provided, which is configured for determining 120, in particular measuring, the total pressure p_ges, which is present in the fuel cell system 100 or at the cathode output 51.The pressure sensor 20 can be connected to the control unit FCCU, particularly via a data connection (shown with a dashed line), especially to transmit the total pressure p_ges to it. An exhaust valve 55 can be provided, which can be connected, in particular, to the cathode output 51. The exhaust valve 55 can be configured to regulate and / or adjust the total pressure p_ges in the fuel cell system 100, particularly at and / or in the cathode output 51. The total pressure p_ges can be adjusted by the exhaust valve 55. For this purpose, the exhaust valve 55 can receive a control signal from the control unit FCCU, particularly via a data connection (shown with a dashed line). An exhaust gas recirculation valve 60 can be provided, which can be connected, in particular, to the cathode output 51 and / or an inlet of the air blower 31.This allows a portion of the products exiting the cathode output 51 to be recirculated, particularly for reinjection into the cathode. The exhaust gas recirculation valve 60 can be configured to regulate and / or adjust the exhaust gas recirculation rate in the fuel cell system 100. The exhaust gas recirculation valve 60 can adjust this rate. For this purpose, the exhaust gas recirculation valve 60 can receive a control signal from the control unit FCCU, particularly via a data connection (shown with a dashed line).

[0071] Fig. Figure 3 shows a system 200, in particular a vehicle 200, comprising a fuel cell system 100 according to the second aspect and / or according to Fig. 2. The System 200 and / or Fuel Cell System 100 may include a control unit FCCU, comprising a computing unit CU and a storage unit MU, in which instructions are stored which, when at least partially executed by the computing unit CU, perform a procedure according to the first aspect and / or Fig. 1.

Claims

[1] Method for operating a fuel cell system (100) wherein at least two [three, all] of the following steps are carried out: - Determine (110), in particular by means of a current sensor (10), a current (I) generated by a fuel cell system (100), - Determine (120), in particular by means of a pressure sensor (20), a total pressure (p_ges) at a cathode output (51) of a cathode (50) of the fuel cell system (100), - Determine (130), in particular by means of an air mass flow sensor (30), an air mass flow (m_dot) entering the cathode (50), and / or - Determine (140), in particular by means of a temperature sensor (40), a temperature (T) of a coolant which is set up to cool the fuel cell system (100), the procedure exhibits: - Calculate (150), by means of a model which is stored in a control unit (FCCU) of the fuel cell system (100), an oxygen partial pressure (p_O2) at the cathode output (51) as a function of the current (I), the total pressure (p_ges), the air mass flow rate (m_dot) and the temperature (T), and - Operation (160) of the fuel cell system (100) by the control unit (FCCU) depending on the calculated oxygen partial pressure (p_O2). [2] Method according to claim 1, characterized by , that the calculation (150) is carried out depending on an ambient humidity, wherein in particular the ambient humidity is determined by measurement by an ambient humidity sensor. [3] Method according to claim 1 or 2, characterized by, that the calculation (150) is performed depending on the position of an exhaust gas recirculation valve (60), wherein in particular the position of an exhaust gas recirculation valve (60) is set by the control unit (FCCU) and / or transmitted to it. [4] Method according to any one of the preceding claims, characterized by that the model comprises a physical model, a data-based model and / or a characteristic curve field-based model, which is determined particularly during commissioning. [5] Method according to any one of the preceding claims, characterized by , that the model is determined by: - Setting (105), by the control unit (FCCU), a multitude of operating points, - Determine (106), in particular by means of a partial pressure sensor (70), for example a mass spectrometer and / or a lambda probe, a plurality of oxygen partial pressures, wherein each oxygen partial pressure of the plurality of oxygen partial pressures is specific for an operating point of the plurality of operating points, - Determining (107), by the control unit (FCCU), the model depending on the multitude of oxygen partial pressures and the multitude of operating points and - Saving (108) the model in the control unit (FCCU). [6] Method according to the preceding claim 5, characterized by , that when setting (105) a large number of operating points, each operating point includes: - Setting a target current, where determining (106) includes: - Determine, in particular by means of a current sensor (10), an actual current, which results in particular depending on the target current, whereby the determination (107) is carried out depending on the actual current. [7] Method according to any one of the preceding claims 5 to 6, characterized by , that, in particular, when setting (105) a large number of operating points, each operating point includes: - Setting a target total pressure, in particular via an exhaust valve (55) which is controlled by the control unit (FCCU), where determining (106) includes: - Determine, in particular by means of the pressure sensor (20), an actual total pressure, which results in particular depending on the target total pressure, where the determination (107) is carried out depending on the actual total pressure. [8] Method according to one of the preceding claims 5 or 7, characterized by , that when setting (105) a large number of operating points, each operating point includes: - Setting a target air mass flow, in particular via an air blower (31) which is controlled by the control unit (FCCU), where determining (106) includes: - Determine, in particular by means of the air mass flow sensor (30), an actual air mass flow, which results in particular depending on the target air mass flow, where the determination (107) is carried out depending on the actual air mass flow. [9] Method according to any one of the preceding claims 5 to 8, characterized by , that when setting (105) a large number of operating points, each operating point includes: - Setting a target temperature for the coolant used to cool the fuel cell system, where determining (106) includes: - Determine, in particular by means of the temperature sensor (40), an actual temperature, which is particularly dependent on the target temperature, where the determination (107) is carried out depending on the actual temperature. [10] Method according to any one of the preceding claims 5 to 9, characterized by , that when setting (105) a large number of operating points, each operating point includes: - Setting a target position of an exhaust gas recirculation valve (60), wherein determining (106) includes: - Determine, in particular by the control unit (FCCU), an actual position of the exhaust gas recirculation valve (60), where the determination (107) is carried out depending on the actual position of the exhaust gas recirculation valve (60). [11] Fuel cell system (100) comprising a control unit (FCCU) configured to implement the method according to any one of the preceding claims 1 to 10. [12] Computer program product comprising instructions which, when the computer program product is executed by a computer, cause it to implement the method according to any one of the preceding claims 1 to 10. [13] Computer-readable data carrier in which instructions are stored which, when executed by a computer, cause it to carry out the method according to any one of the preceding claims 1 to 10. [14] Control unit (FCCU) comprising a computing unit (CU) and a storage unit (MU) in which instructions are stored which, when at least partially executed by the computing unit (CU), perform a method according to any one of the preceding claims 1 to 10. [15] System (200), in particular vehicle (200), comprising a fuel cell system (100) according to claim 11 and / or a control unit (FCCU) according to claim 14.

Images