Method for determining a gas composition in an anode section of a fuel cell stack with anode gas circulation

Abstract

The present invention relates to a method for determining a gas composition (GZ) in an anode section (120) of a fuel cell stack (110) of a fuel cell system (100), comprising the following steps: - detecting an anode pressure (AD) for the anode section (120) of the fuel cell stack (110); - detecting an actual electrical power (IL) of a recirculation device (140) for a recirculation of an anode exhaust gas (AAG) from an anode discharge section (124) via a recirculation section (140) into an anode supply section (122) of the anode section (120) of the fuel cell stack (110); and, - determining a current gas composition (GZ) of the anode exhaust gas (AAG) based on the detected anode pressure (AD) and the detected actual electrical power (IL).

Description

[0001] METHOD FOR DETERMINING A GAS COMPOSITION IN AN ANODE SECTION OF A FUEL CELL STACK WITH ANODE GAS CIRCULATION

[0002] The present invention relates to a determination method for determining a gas composition in an anode section of a fuel cell stack of a fuel cell system, a computer program product for carrying out such a determination method, a control device for carrying out such a determination method, a fuel cell system with such a control device, and a calibration method for calibrating a determination step of a determination method.

[0003] It is known that when operating fuel cell systems, the most accurate possible knowledge of the gas composition, particularly on the anode side of a fuel cell stack, is advantageous. This value is especially useful for increasing the efficiency of the fuel cell system and / or for diagnosing the current wear level of individual fuel cells within the stack. Known solutions therefore involve an assumption or estimation of this gas composition; however, a direct measurement of this value integrated into a fuel cell system is not yet possible. This assumption is therefore solely an estimation and thus subject to the corresponding estimation errors.

[0004] Due to the reliance on estimating gas composition, current control methods for fuel cell systems lack the necessary accuracy. Therefore, during operation, it is currently necessary to ensure that the desired limits for gas composition are maintained, using a safety factor. While this achieves the desired and required operational safety, it results in a loss of efficiency.

[0005] The object of the present invention is to at least partially overcome the disadvantages described above. In particular, it is an object of the present invention to obtain, in a cost-effective and simple manner, the most accurate possible information about the gas concentration on the anode side of a fuel cell stack. The above object is achieved by a determination method with the features of claim 1, a computer program product with the features of claim 12, a control device with the features of claim 13, a fuel cell system with the features of claim 14, and a calibration method with the features of claim 15. 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 determination method according to the invention naturally also apply in connection with the computer program product according to the invention, the control device according to the invention, the fuel cell system according to the invention and the calibration method according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, mutual reference is always made or can be made.

[0006] A determination method according to the invention serves to determine a gas composition in an anode section of a fuel cell stack of a fuel cell system. Such a determination method is characterized by the following steps:

[0007] - Measuring the anode pressure for the anode section of the fuel cell stack,

[0008] - Recording the actual electrical power of a recirculation device for recirculating an anode exhaust gas from an anode discharge section via a recirculation section into an anode supply section of the anode section of the fuel cell stack,

[0009] - Determining the current gas composition of the anode exhaust gas based on the measured anode pressure and the measured actual electrical power.

[0010] The core concept of the invention is based on the use of a virtual sensor for the direct determination of gas composition. Instead of a physical gas sensor, the determination is carried out by utilizing the measurement of other operating parameters. This is significantly simpler than explicitly measuring gas compositions. Accurate analysis of gas composition typically requires complex measurement methods. For example, gas chromatography is a known technique, which requires passing the respective gas stream through a specialized device. While such complex measurement methods are suitable for use on a test bench, they are inefficient and impractical for daily operation at the point of use with a fuel cell system.

[0011] The corresponding fuel cell system is specifically designed as a PEM fuel cell system.

[0012] The anode pressure for the anode section of the fuel cell stack and / or the actual electrical power of a recirculation device are measured, in particular physically.

[0013] Within the scope of the present invention, operating parameters that can be determined much more easily are now recorded. One of these is a pressure value, namely the pressure in the anode section of the fuel cell stack. Since information about the pressure is necessary for the usual operation of a fuel cell system, known fuel cell stacks already have corresponding pressure sensors. In other words, a determination method according to the invention can thus utilize existing sensor elements. As will be explained later, this makes the use of such a determination method considerably simpler and, above all, fundamentally possible to retrofit into existing fuel cell systems.

[0014] As a further operating parameter, the current electrical power drawn from a recirculation device is determined here. It is known that in fuel cell systems, at least a portion of the resulting anode exhaust gas is recirculated back into the anode feed section to achieve the most precise possible stoichiometry in the anode section. This recirculation is called recirculation. Since this recirculation is usually performed actively, recirculation devices are used, for example, in the form of recirculation fans. The energy requirement for active recirculation can be determined, which can be defined as the electrical power of the respective recirculation device. Similar to the well-known and very simple pressure determination for the first operating parameter, a very simple and cost-effective determination of this electrical power requirement in the form of the actual electrical power of the recirculation device is also possible.

[0015] As can be seen from the two preceding paragraphs, two operating parameters can now be recorded as input values ​​in a determination method according to the invention, which can be recorded based on existing sensor elements. Therefore, no new or additional sensor elements are necessary for these two recording steps.

[0016] In the final step of a determination method according to the invention, the current gas composition is determined. For this determination, the measured anode pressure and the measured actual electrical power of the recirculation device are used as the basis. For this determination step, a determination relationship is used, which will be explained in more detail later with regard to various embodiments. This determination relationship, or other determination methods for this step, are based in particular on information from tests on a test bench. For example, a fuel cell system can be operated on a test bench that has a capability for analyzing the gas composition. Gas chromatography, for instance, can be used here.In addition to the actual gas composition recorded on the test bench, the corresponding operating parameters, in the form of anode pressure and the actual power output of the recirculation device, are also recorded for each operating time. This creates a unified picture of the relationship between these three data sets. This relationship can then be incorporated into the aforementioned determination process. Alternatively, the determination step can also be carried out based on simulations and / or on physically based relationships.

[0017] Based on the known relationships between the input values—now easily and cost-effectively obtainable in the form of anode pressure and actual electrical power—the current gas composition can now be determined simply, accurately, and, above all, with minimal computational effort. By utilizing the relationships identified in the test bench experiments, a significantly more precise determination of the gas composition is possible than with previous methods and estimations. All subsequent control interventions, such as those of a control system for the operation of the fuel cell system, can thus rely on more accurate and meaningful gas composition values.

[0018] In addition to its use for operational monitoring of the fuel cell system, it can also be used for diagnostics. Information about the gas composition is essential for the operation and, above all, for detecting potential damage mechanisms in fuel cell systems. For example, based on specific gas concentrations, one or more different damage situations can be precisely identified. It is also possible to record the duration of these respective damage situations and use this data as the basis for a damage diagnosis. This not only makes the current operation of the fuel cell system more efficient but also allows for more precise monitoring of the current damage status of individual fuel cells.

[0019] When determining the gas composition in the anode exhaust gas, the three expected main components are specifically identified: hydrogen, nitrogen, and water. If the fuel cell system has a controllable and therefore variable recirculation rate, the correspondingly set recirculation rate can be used as an additional operating parameter for the determination.

[0020] A determination method according to the invention makes it possible, in a first step, to optimize the operational control of the fuel cell system. This optimization aims in particular at increasing efficiency and / or reducing undesirable damage mechanisms. A further advantage is its applicability in the aforementioned diagnostic procedures. More precise information and diagnosis of the damage rate can lead to the timely replacement of components and / or a longer operating life for the fuel cell system. Ultimately, this results in an increased service life for the individual components as well as the entire fuel cell system.

[0021] Furthermore, monitoring the gas composition allows for the identification of component failures. In particular, components used by the fuel cell system's operational control to adjust the gas composition can be monitored and tested for functionality.

[0022] A further advantage is that regeneration processes in the fuel cell system, such as purging, can be adapted to the actual situation. This applies in particular to the described diagnostic options and the described damage rate of the fuel cells. Since such regeneration processes are associated with a reduction in operating efficiency and, in the case of purging, also with a loss of fuel gas, a targeted and therefore reduced number of such processes is advantageous. Within the scope of the inventions, purging refers specifically to the draining of water from the anode circuit. Purging can also advantageously be described as a flushing process.

[0023] Advantages can arise if, in a determination method according to the invention, the steps of measuring the anode pressure, measuring the actual electrical power, and determining the current gas composition are repeated multiple times, particularly continuously. This can especially serve as ongoing monitoring of the fuel cell system's operation. The output, in the form of the determined gas composition, can be integrated into the fuel cell system's operational control. This makes it possible not only to perform the aforementioned diagnostic steps but also to establish a control signal and / or a control loop that allows monitoring of the gas composition in the anode section of the fuel cell system. In other words, the virtual sensor technology of the determination method makes it possible to actively integrate the gas composition into the operational control of the fuel cell system.

[0024] It can be further advantageous if, in a determination method according to the invention, a rate of change is determined for the anode pressure, the actual electrical power, and / or the current gas composition. This refers in particular to the change in the gas composition or the two measured operating parameters over time. This makes it possible for operational monitoring to determine the monitoring rate and thus the rate of influence of a control change. With regard to damage diagnosis, the rate of change can also provide additional information to track the damage rate and / or an aging rate as accurately as possible. Furthermore, this makes it possible to precisely identify emergency situations and to shut down the fuel cell system in a timely manner to prevent the destruction and / or irreversible damage of individual components.

[0025] It can also be advantageous if, in a determination method according to the invention, the current gas composition is determined using a determination relationship established on a test bench, particularly in the form of a characteristic map, which contains a correlation between the anode pressure, the actual electrical power, and the gas composition. As already explained with regard to claim 1, significantly more sophisticated sensors can be used on a test bench. These allow, in particular through actual measurement, the gas composition to be recorded in temporal relation to the operating parameters in the form of the anode pressure and the actual power of the recirculation device. Thus, the corresponding relationships of these three parameters are known on the test bench for different operating conditions of the fuel cell system and can be stored in the determination relationship.A particularly simple implementation of such a determination relationship is a characteristic map for the aforementioned parameters. Such a characteristic map can also be referred to as a look-up table. With regard to its use for determining gas composition, such a characteristic map can offer a very computationally efficient approach. Alternatively or additionally, algorithmic relationships can also be determined as a determination relationship on the test bench or separately. It is also possible to incorporate physical relationships into the determination relationship.

[0026] Furthermore, advantages can arise if, in a determination method according to the invention, the current operating situation of the fuel cell system is additionally recorded and taken into account when determining the current gas composition. In particular, static operating situations can be distinguished from dynamic operating situations. Dynamic operating situations include, for example, load changes on the fuel cell system, start-up processes, or shutdown processes. In such dynamic operating situations, correspondingly different relationships between the aforementioned operating parameters and the gas composition may be relevant, so that, in particular, different determination relationships can be determined on the test bench and used in the determination method for different operating situations.Alternatively or in addition to different determination relationships, correction factors relating to the identified operational situation can also be used for a single determination relationship.

[0027] Furthermore, advantages can be gained if, in a determination method according to the invention, the actual electrical power is measured by means of a power control of the recirculation device itself and / or by means of an operational control of the fuel cell system. A combination of these two measurement methods is also conceivable within the scope of the present invention. In both cases, existing power sensors can be used, namely those of the operational control of the fuel cell system and / or the power control of the recirculation device. Thus, existing components can be used, so that the determination method according to the invention can also be used with existing fuel cell systems and can even be retrofitted via a software update.

[0028] Further advantages arise when, in a determination method according to the invention, the anode pressure is measured in the anode supply section of the anode section of the fuel cell stack. Because a substantially constant pressure prevails in the anode section of the fuel cell stack, the anode pressure can be measured at various possible locations. In this embodiment, a position is chosen where a pressure sensor is typically already present in existing fuel cell systems. This allows the use of an existing component for pressure measurement, thereby reducing the effort required to implement the determination method in existing fuel cell systems. This applies to both fuel cell systems in regular operation and those on the test bench.

[0029] Furthermore, it is advantageous if an active recalibration for determining the current gas composition is performed in a determination method according to the invention, in particular by actively increasing the fuel gas concentration in the anode exhaust. Over a longer operating period of the fuel cell system, the actual behavior of the two operating parameters for measurement may deviate from the test bench trials. To compensate for this deviation, recalibration can be performed. For example, one or more purging processes are conceivable. Alternatively or additionally, increasing the fuel gas supply is also possible as part of such recalibration. Both steps serve in particular to maximize the concentration of fuel gas, for example, in the form of hydrogen. This maximized concentration state can also be referred to as the standardized concentration state or recalibration state.The result of this calibration can be used directly in a relationship to adjust it, or applied as a correction factor to the result from a relationship.

[0030] Further advantages can be achieved if, in a determination method according to the invention as described in the preceding paragraph, active recalibration is performed at regular intervals and / or based on a trigger signal. For example, it may be known from test bench trials after which recalibration is necessary. This knowledge can be used for this embodiment so that recalibration is carried out in good time. Alternatively or additionally, recorded operating parameters, in particular based on detected deviations from expected behavior, can provide a trigger signal for performing the recalibration. In particular, it is possible to perform a plausibility check on the recorded operating parameters and to use a negative result of this check as a trigger signal.

[0031] Furthermore, it can be advantageous if, in a determination method according to the invention, at least one of the following parameters is determined based on the current gas composition, in particular based on a gradient of the current gas composition:

[0032] - Diffusion rate between anode section and a cathode section of the fuel cell stack,

[0033] Leakage rate in the anode section. The preceding list is not exhaustive. Other measured values ​​can also be used. As a result of this additional determination, an alarm signal can be issued, for example. This applies in particular if a predefined limit is exceeded for the diffusion rate and / or the leakage rate. The additional determination of these two rates is particularly advantageous for the diagnostic system explained several times. For example, the diffusion rate between the two sections of the fuel cell stack can depend, in particular, on the wear of the membrane in the fuel cells. Thus, the degree of wear and therefore the aging state of the membrane in the fuel cells can be inferred indirectly from the diffusion rate.

[0034] In the context of the invention, a leakage rate is to be understood in particular as a rate for hydrogen escaping from the system or the line.

[0035] Further advantages can arise if, in a determination method according to the invention, at least one of the following control interventions for the operation of the fuel cell system is determined based on the current gas composition:

[0036] - Purging process

[0037] - Supply of fuel gas to the anode section

[0038] - Recirculation rate through the recirculation section

[0039] The preceding list is also non-exhaustive. In addition to its use for diagnosing the fuel cell system, the specific control interventions mentioned for this embodiment are particularly advantageous for direct operational monitoring. One or more control interventions can be defined to achieve various objectives, such as reducing wear, increasing operational efficiency, or other optimization goals. Compared to known solutions, these interventions allow for consideration of the actual gas composition and corresponding adjustments. This enables more precise and improved control compared to existing solutions, leading to more efficient operation and reduced wear of the fuel cells.Another object of the present invention is a computer program product comprising instructions which, when executed by a computer, cause it to perform the steps of a determination method according to the invention. Thus, a computer program product according to the invention also offers the same advantages as those explained in detail with reference to a determination method according to the invention.

[0040] Furthermore, the present invention relates to a control device for determining the gas composition in an anode section of a fuel cell stack of a fuel cell system. Such a control device is characterized by a pressure sensing module for detecting the anode pressure of the anode section of the fuel cell stack. A power sensing module is also provided for detecting the actual electrical power of a recirculation device for recirculating anode exhaust gas from an anode discharge section, via a recirculation section, into an anode supply section of the anode section of the fuel cell stack. Finally, a determination module is provided for determining the current gas composition of the anode exhaust gas based on the detected anode pressure and the detected actual electrical power.The pressure detection module, the power detection module, and / or the determination module are configured for an embodiment of a determination method according to the invention. A control device according to the invention thus offers the same advantages as those explained in detail with reference to the determination method according to the invention.

[0041] Another object of the present invention is a fuel cell system with at least one fuel cell stack, comprising an anode section and a cathode section. The anode section has an anode supply section for supplying anode supply gas and an anode discharge section for removing anode exhaust gas. Furthermore, the cathode section has a cathode supply section for supplying cathode supply gas and a cathode discharge section for removing cathode exhaust gas. A recirculation section is also provided, which fluidly connects the anode discharge section to the anode supply section for recirculating at least a portion of the anode exhaust gas into the anode supply section by means of a recirculation device.A fuel cell system according to the invention is characterized in that a control device according to the present invention is provided for determining the gas composition in the anode section and for carrying out a determination method according to the present invention. A fuel cell system according to the invention also offers the same advantages as those explained in detail with reference to a determination method according to the invention. The fuel cell system according to the invention is particularly well-designed as a PEM fuel cell system.

[0042] Furthermore, another object of the present invention is a calibration method for calibrating a determination step for a current gas composition in a determination method according to the present invention. This calibration method is characterized by the following steps:

[0043] - Operating a fuel cell system, in particular according to the present invention, on a test bench,

[0044] - Direct measurement of the gas composition in the anode section, the anode pressure, and the actual electrical power of the recirculation device,

[0045] - Establishing a relationship between the directly measured gas composition in the anode section, the anode pressure, and the actual electrical power.

[0046] A calibration method according to the invention also offers the same advantages as those explained in detail with reference to a determination method according to the invention. The determination relationship can, for example, be designed as a characteristic map. Additionally or alternatively, an algorithmic relationship is also possible. The detailed data measured on the test bench for both input operating parameters, as well as the gas composition to be determined, allow for the calibration of this determination relationship. In other words, calibration is achieved by generating one or even several different determination relationships, which can then be used in the operation of the fuel cell system for the determination method.

[0047] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The drawings schematically show:

[0048] Fig. 1 shows a possible embodiment of a fuel cell system according to the invention,

[0049] Fig. 2 shows a possible embodiment of a control device according to the invention,

[0050] Fig. 3 shows another possible embodiment of a control device according to the invention, and

[0051] Fig. 4 shows another possible embodiment of a control device according to the invention,

[0052] Figure 1 shows a fuel cell system 100 of the present invention. This system is equipped with a fuel cell stack 110. The fuel cell stack 110 has an anode section 120 and a cathode section 130. An anode supply section 122 is provided for supplying anode supply gas AZG to the anode section 120. An anode discharge section 124 is provided for removing the anode exhaust gas AAG generated in the fuel cell stack 110. Similarly, the cathode section 130 is equipped with a cathode supply section 132 for supplying cathode supply gas KZG and a cathode discharge section 134 for removing cathode exhaust gas KAG.

[0053] Depending on the operating state, a portion of the anode exhaust gas AAG can be recirculated into the anode section 122 via a recirculation section 140 to define the gas composition GZ in the fuel cell stack 110. A recirculation device 142, for example in the form of a recirculation fan, is provided for precise control of this recirculation and active intervention in the recirculation rate.

[0054] According to the present invention, a control device 10 is provided to carry out the determination method according to the present invention. As can be seen in Figure 1, the control device 10 therefore detects the anode pressure AD and the actual electrical power IL. The further course of the determination method is explained in more detail with reference to the following figures. As can also be clearly seen in Figure 1, the measurement of the anode pressure AD is carried out on the inlet side of the anode section 120 of the fuel cell stack 110. This allows the use of a pressure sensor, which is already part of the existing operational control of the fuel cell system 100.

[0055] Figure 2 shows a particularly simple embodiment of a control device 10 according to the present invention. Here, two parallel detection modules are provided, in the form of the pressure detection module 20 and the power detection module 30. These two detection modules can communicate with sensor elements of the fuel cell system 100 or themselves contain such sensor elements. They are thus able to detect the two operating parameters, namely the anode pressure AD and the actual power IL, as input values ​​for the determination method of the present invention. The two detected operating parameters are then transferred to the determination module 40. In the determination module 40, the gas composition GZ is determined and this value is output. The method of this determination is explained in more detail with reference to the following figures.

[0056] Figure 3 illustrates one possibility that utilizes a BB determination relationship. Schematically, this figure represents the BB determination relationship as a characteristic curve or map. Using the two input values—the anode pressure AD on the X-axis and the actual electrical power IL on the Y-axis—a corresponding value for the gas composition GZ, determined by the test bench, can be read. Alternatively or additionally to such a map, the BB determination relationship can also exhibit an algorithmic relationship.

[0057] Figure 4 also shows a similar solution, which, however, takes an additional input value into account. This is the current operating situation BS. This operating situation BS distinguishes, in particular, between a dynamic and a static operating situation BS. As Figure 4 shows, specific determination relationships BB are available for each of the different operating situations BS. In this case, for example, there are two different determination relationships BB. Depending on the currently recorded operating situation BS, the appropriate determination relationship BB, which is calibrated accordingly on the test bench for this operating situation BS, is used. As an alternative to different operating relationships BB, correction factors are also conceivable, which are multiplied by the read value of the gas composition GZ from a single operating relationship BB.

[0058] The preceding explanation of the embodiments describes the present invention exclusively by way of examples.

[0059] Reference symbol list

[0060] 10 Control device

[0061] 20 Print Capture Module

[0062] 30 Performance Recording Module

[0063] 40 Determination module

[0064] 100 fuel cell systems

[0065] 110 fuel cell stacks

[0066] 120 anode section

[0067] 122 Anode feed section

[0068] 124 Anode discharge section

[0069] 130 Cathode section

[0070] 132 Cathode feed section

[0071] 134 Cathode discharge section

[0072] 140 Recirculation section

[0073] 142 Recirculation device

[0074] AD anode pressure

[0075] IL Actual Performance

[0076] GZ Gas composition

[0077] BS operational situation

[0078] BB Determination relationship

[0079] AZG anode supply gas

[0080] AAG anode exhaust

[0081] KZG cathode supply gas

[0082] KAG cathode exhaust

Claims

Patent claims 1. Method for determining a gas composition (GZ) in an anode section (120) of a fuel cell stack (110) of a fuel cell system (100), comprising the following steps: - Measuring an anode pressure (AD) for the anode section (120) of the fuel cell stack (110), - Recording an actual electrical power (IL) of a recirculation device (140) for recirculating an anode exhaust gas (AEG) from an anode discharge section (124) via a recirculation section (140) into an anode supply section (122) of the anode section (120) of the fuel cell stack (110), - Determining the current gas composition (GZ) of the anode exhaust gas (AAG) based on the measured anode pressure (AD) and the measured actual electrical power (IL).

2. Determination method according to claim 1, characterized in that the steps of detecting the anode pressure (AD), detecting the actual electrical power (IL) and determining the current gas composition (GZ) are repeated several times, in particular continuously.

3. Determination method according to one of the preceding claims, characterized in that a change gradient is determined for the anode pressure (AD), the actual electrical power (IL) and / or the current gas composition (GZ).

4. Determination method according to one of the preceding claims, characterized in that the determination of the current gas composition (GZ) is carried out using a determination relationship (BB) created on a test bench, in particular in the form of a characteristic map which contains a correlation between the anode pressure (AD), the actual electrical power (IL) and the gas composition (GZ).

5. Determination method according to one of the preceding claims, characterized in that an additional current operating situation (BS) of the fuel cell system (100) is recorded and taken into account when determining the current gas composition (GZ).

6. Determination method according to one of the preceding claims, characterized in that the actual electrical power (IL) is determined by means of a power control of the recirculation device (142) itself and / or by means of an operational control of the fuel cell system (100).

7. Determination method according to one of the preceding claims, characterized in that the anode pressure (AD) is detected in the anode supply section (122) of the anode section (120) of the fuel cell stack (110).

8. Determination method according to one of the preceding claims, characterized in that an active recalibration is carried out for the determination of the current gas composition (GZ), in particular by actively increasing a fuel gas concentration in the anode exhaust gas (AAG).

9. Determination method according to claim 8, characterized in that the active recalibration is carried out at regular intervals and / or on the basis of a trigger signal.

10. Determination method according to one of the preceding claims, characterized in that at least one of the following parameters is determined on the basis of the current gas composition (GZ), in particular on the basis of a gradient of the current gas composition (GZ): - Diffusion rate between anode section (120) and a cathode section (130) of the fuel cell stack (110), - Leakage rate in the anode section (120).

11. Determination method according to one of the preceding claims, characterized in that it is based on the current gas composition (GZ) at least one of the following control interventions is determined for the operation of the fuel cell system (110): - Purging process - Supply of fuel gas to the anode section (120) - Recirculation rate through the recirculation section (140) 12. Computer program product comprising instructions which, when executed by a computer, cause it to perform the steps of a determination method having the features of any one of claims 1 to 11.

13. Control device (10) for determining a gas composition (GZ) in an anode section (120) of a fuel cell stack (110) of a fuel cell system (100), characterized by a pressure sensing module (20) for sensing an anode pressure (AD) for the anode section (120) of the fuel cell stack (110), a power sensing module (30) for sensing an actual electrical power (IL) of a recirculation device (142) for recirculating an anode exhaust gas (AEG) from an anode discharge section (124) via a recirculation section (140) into an anode supply section (122) of the anode section (120) of the fuel cell stack (110), and a determination module (40) for determining a current gas composition (GZ) of the anode exhaust gas (AEG) based on the detected anode pressure (AD) and the measured actual electrical power (IL), wherein the pressure sensing module (20),the power acquisition module (30) and / or the determination module (40) are configured for an embodiment of a determination method having the features of one of claims 1 to 11.

14. Fuel cell system (100) with at least one fuel cell stack (110), comprising an anode section (120) and a cathode section (130), the anode section (120) comprising an anode supply section (122) for supplying anode supply gas (AZG) and an anode discharge section (124) for removing anode exhaust gas (AAG), the cathode section (130) comprising a cathode supply section (132) for supplying cathode supply gas (CSG) and a cathode discharge section (134) for the discharge of cathode exhaust gas (CEG), wherein a recirculation section (140) further connects the anode discharge section (124) with the anode supply section (122) in a fluid-communicating manner for the recirculation of at least a part of the anode exhaust gas (AEG) into the anode supply section (122) by means of a recirculation device (142), characterized in that a control device (10) with the features of claim 13 for carrying out a determination method with the features of one of claims 1 to 11 is provided for determining the gas composition (GZ) in the anode section (120).

15. Calibration method for calibrating a determination step for a current gas composition (GZ) in a determination method having the features of one of claims 1 to 11, characterized by the following steps: - Operating a fuel cell system (100), in particular with the features of claim 14, on a test bench, - Direct measurement of the gas composition (GZ) in the anode section (120), the anode pressure (AD) and the actual electrical power (IL) of the recirculation device (142), Establishing a relationship (BB) between the directly measured gas composition (GZ) in the anode section (120), the anode pressure (AD) and the actual electrical power (IL).

Images