FUEL CELL CONTROL METHOD

Description

State of the art

[0001] A fuel cell control method for controlling an operating parameter, in particular fuel utilization, of a fuel cell device, in particular a solid oxide fuel cell device, has already been proposed.

[0002] For example, EP 1 139 473 A2 discloses a fuel cell system and a method for operating a fuel cell system. DE 196 20 501 C1 also discloses a method for operating a fuel cell arrangement. DE 10 2004 025229 A1 discloses a fuel cell system with a cathode material stream. Disclosure of the invention

[0003] The invention is based on a fuel cell control method for controlling an operating parameter, in particular a fuel utilization, of a fuel cell device, in particular a solid oxide fuel cell device.

[0004] It is proposed that the fuel cell device comprises a measuring unit for detecting compositions of fluids exiting from at least two fuel cell units connected in parallel, in particular anode outlet gases.

[0005] Furthermore, it is proposed that the measuring unit for at least two parallel-connected fuel cell units of the fuel cell device comprises at least one lambda probe each, in particular one broadband lambda probe each.

[0006] It is proposed that in at least one method step the operating parameter is controlled as a function of compositions of fluids exiting from at least two fuel cell units connected in parallel, in particular anode outlet gas.

[0007] A "fuel cell device" is understood, in particular, to be a device comprising at least one fuel cell with a cathode and an anode. The fuel cell device preferably has at least one fluid supply line each to the cathode and to the anode of the fuel cell, as well as at least one fluid discharge line. Preferably, at least one fluid supply line is provided for conducting a fluid fuel, for example, a hydrogen and / or hydrocarbon mixture, in particular to the anode. Preferably, at least one, in particular further, fluid supply line is provided for conducting a fluid oxidant, for example, an oxygen mixture, in particular to the cathode. The fluid discharge line is preferably provided for discharging a fluid emerging from the anode, in particular an at least partially oxidized fuel.An "operating parameter" is to be understood in particular as a variable that characterizes the operation of the fuel cell device, in particular the combustion process in the at least one fuel cell. The operating parameter preferably characterizes the efficiency of the operation, in particular the consumption of resources. Particularly preferably, the operating parameter is embodied as fuel utilization. "Fuel utilization" is to be understood in particular as a proportion of the fuel oxidized by the fuel cell in relation to an oxidizable proportion of the fuel before passing through the fuel cell. In an alternative embodiment, the operating parameter could also be embodied analogously as oxidant utilization.The operating parameter can preferably be determined based on supply parameters, for example a quantity of fuel supplied, in particular per unit of time, and / or a quantity of oxidant supplied, and / or process parameters, for example a temperature and / or a pressure within the fuel cell. In particular, to determine the operating parameter, the fuel that is at least partially oxidized in the fuel cell is examined with regard to its chemical composition upon exiting the fuel cell device, in particular upon exiting the fuel cell. In particular, to determine the operating parameter, a relative and / or absolute proportion of at least one substance in the exiting fluid is recorded. Preferably, the operating parameter is kept essentially constant at all times in at least one method step by means of a control system."Essentially always constant" is understood in particular to mean that the operating parameter deviates from a target value by less than 5%, preferably less than 1%, for at least 90% of the duration of the process step. In an alternative embodiment, periodic control is also conceivable. In particular, the operating parameter is controlled based on a measurement and / or adjustment of supply parameters and / or process parameters. Preferably, the composition of the exiting fluid serves as a controlled variable for controlling the operating parameter.

[0008] "Intended" should be understood in particular to mean specifically programmed, designed, and / or equipped. The fact that an object is intended for a specific function should be understood in particular to mean that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0009] The inventive design of the fuel cell control method advantageously ensures that an operating parameter, in particular fuel utilization, is maintained at a design-dependent permissible extreme value despite fluctuating supply parameters, in particular fluctuations in fuel composition. In particular, a fuel cell device can be operated safely at maximum efficiency despite fluctuating supply parameters.

[0010] It is further proposed that, in at least one method step, the exiting fluid be evaluated for a relative oxidant content, in particular oxygen content. In particular, an "oxidant content" can be understood as a concentration of an oxidant and / or a concentration of a substance that combines with an oxidant, in particular unreacted fuel. A relative oxidant content preferably describes an oxidant deficiency and / or an oxidant excess of the exiting fluid compared to a stoichiometric mixing ratio of fuel and oxidant. In particular, the oxidant content of the exiting fluid is compared with a reference sample. The reference sample is preferably a fluid with a known oxidant content. An oxidation ratio of the exiting fluid, in particular a combustion air ratio, is preferably determined from a difference in the oxidant content.In particular, the oxidation ratio describes a ratio of an oxidized portion of the exiting fluid to the oxidized and still oxidizable portion. In particular, the oxidized portion of the exiting fluid can be composed of a portion oxidized by the fuel cell and a portion already previously oxidized. Preferably, the operating parameters are determined based on the oxidation ratio, particularly taking into account other supply parameters and / or process parameters. The inventive design of the fuel cell control method advantageously allows the operating parameters to be determined easily. Advantageously, the operating parameters can already be determined by partially detecting the composition of the exiting fluid.

[0011] It is further proposed that, in at least one method step for regulating the operating parameter, the supplied amount of an oxidant carrier, in particular water, is detected. An "oxidant carrier" is to be understood, in particular, as a chemical compound from which an oxidant can be split off. Preferably, the amount of an oxidant carrier and / or oxidant supplied to the fuel before the fuel cell is detected, in particular measured. Preferably, the supplied amount of an oxidant carrier and / or oxidant is detected before being added to the fuel. Preferably, a fuel is enriched with water before reaching the fuel cell. Alternatively, the fuel is enriched with oxygen before reaching the fuel cell. Preferably, the proportion of an oxidant in the fuel, in free or bound form, before reaching the fuel cell is determined from the supplied amount of the oxidant carrier and / or oxidant.The inventive design of the fuel cell control method advantageously allows the operating parameter, in particular the oxidation ratio, to be determined even when an oxidant carrier and / or an oxidant is admixed to the fuel upstream of the fuel cell. Advantageously, an oxidant and / or oxidant carrier can be supplied from an external source and / or a storage device to reform the fuel gas upstream of the fuel cell.

[0012] Furthermore, it is proposed that, in at least one method step, the composition of the fluid exiting the fuel cell device, in particular anode outlet gas, is used to adjust at least one supply parameter of the fuel cell device, in particular a fuel quantity and / or an oxygen quantity. In particular, a "supply parameter" is to be understood as a variable that describes a quantity of a resource available to the fuel cell for a combustion process. In particular, the resource can be material, for example, the fuel quantity, or energetic, for example, a heat quantity. A quantity can be recorded, for example, as mass, volume, and / or number. In particular, a supply parameter can also be configured as a quantity per unit of time, for example, as a material flow.Preferably, the fuel cell device is provided to supply the resource to the fuel cell, in particular the anode, in particular from an external source and / or a reservoir. Preferably, an adjustment of a supply parameter for regulating the operating parameter is determined from the composition of the fluid exiting the fuel cell device, in particular from the anode. In particular, it is determined from the composition of the fluid exiting the fuel cell device, upon reaching a specified value of the operating parameter, whether there is a fuel deficiency or an oxidant deficiency, in particular in the anode. Preferably, depending on the composition of the fluid exiting the fuel cell device, a fuel quantity is adjusted upstream of the fuel cell by means of a fluid control unit, in particular a valve, a compressor and / or a pump.Preferably, an oxidant quantity, formed as an ion current diffusing in particular through an electrolyte between the anode and cathode, is regulated depending on the composition of the fluid exiting the fuel cell device. In particular, the oxidant quantity is adjusted by limiting the electrical current flowing between the cathode and the anode. Preferably, a relationship to a further supply parameter is changed by adjusting at least one supply parameter. In particular, a ratio of the fuel quantity to the electrical current flowing between the cathode and the anode is adjusted depending on the composition of the fluid exiting the fuel cell device. In a further embodiment, it is also conceivable for the supply parameters to be recorded.In particular, the adjustment of a supply parameter for controlling the operating parameter can itself be controlled by detecting the supply parameter. The inventive design of the fuel cell control method advantageously allows for compensation of a fluctuation in a supply parameter, in particular a fluctuation in the composition of a fuel.

[0013] It is further proposed that, in at least one method step, a safety function changes an operating mode of the fuel cell device depending on a composition of the fluid exiting the fuel cell device. In particular, the safety function is provided to intervene in the control of the operating parameter, in particular to stop the control and / or operation of the fuel cell device. Preferably, the safety function detects, based on at least one termination criterion, whether the fuel cell device is operating within a specified operating range. In particular, at least one termination criterion depends on a composition of the fluid exiting the fuel cell device. For example, exceeding or falling below a permissible extreme value of the operating parameter is a termination criterion.For example, a termination criterion could be the exceeding of a maximum tolerance time within which the operating parameter may deviate from a target value. For example, reaching a limit value of a supply parameter is a termination criterion. The safety function preferably distinguishes between hard termination criteria, where operation is stopped immediately, and soft termination criteria, where operation is reduced and / or at least one further termination criterion must be met before the safety function intervenes in operation. The safety function preferably issues a warning when a termination criterion is reached. The safety function preferably intervenes in the operation of the fuel cell device via additional safety units, for example safety valves. Alternatively, the safety function takes over control of the supply parameters.The inventive design of the fuel cell control method advantageously allows for the detection of a leak within the fuel cell device. Damage to the fuel cell device can advantageously be avoided.

[0014] Furthermore, the invention is based on a fuel cell device, in particular a solid oxide fuel cell device, with at least one control device for controlling an operating parameter, in particular fuel utilization, in particular by means of a fuel cell control method according to the invention. It is proposed that the fuel cell device has a measuring unit for detecting a composition of a fluid exiting the fuel cell device, in particular anode outlet gas. Preferably, the fuel cell device comprises at least one fuel cell. Particularly preferably, the fuel cell device comprises at least one fuel cell unit. In particular, a fuel cell unit comprises at least one, preferably several, fuel cells with common inlet and outlet openings. Preferably, the control device comprises at least one computing unit.A "computing unit" is understood, in particular, to be a unit with an information input, an information processing unit, and an information output. The computing unit preferably has at least one processor, a memory, input and output means, further electrical components, an operating program, control routines, control routines, and / or calculation routines. The components of the computing unit are preferably arranged on a common circuit board and / or advantageously arranged in a common housing. The computing unit is preferably designed to process data originating from the measuring unit, in particular to determine an operating parameter. The control device preferably comprises at least one fluid control unit, in particular a pump, a compressor, and / or a valve, arranged on the fluid supply lines transporting the fuel, for controlling the fuel quantity.The control device preferably comprises a current control unit for controlling the electrical current flowing between the anode and cathode. The control device preferably comprises at least one further measuring unit for detecting a supply parameter. The inventive design of the fuel cell device advantageously ensures that an operating parameter, in particular fuel utilization, is maintained at a design-dependent permissible extreme value despite fluctuating supply parameters, in particular fluctuations in the fuel composition. In particular, a fuel cell device can be operated safely at maximum efficiency despite fluctuating supply parameters.

[0015] Furthermore, it is proposed that the measuring unit for at least two fuel cell units of the fuel cell device connected in parallel comprise at least one lambda probe each, in particular one broadband lambda probe each. In particular, the lambda probe is provided to detect an oxygen content of the fluid exiting the fuel cell device. Preferably, the lambda probe determines the oxidation ratio of the fluid exiting the fuel cell device, in particular of the fluid exiting at the anode outlet of the fuel unit. In an alternative embodiment, the measuring unit could also comprise a mass spectrometer, an infrared spectrometer and / or another analysis unit deemed appropriate by a person skilled in the art to detect the composition of the fluid exiting the fuel cell device.Due to the design of the fuel cell device according to the invention, an oxygen content of the fluid exiting the fuel cell device can advantageously be detected in a simple and cost-effective manner in order to determine and / or control the operating parameter.

[0016] "Connected in parallel" is understood, in particular, to mean that the fluid supply line transporting the fuel has a line branch, with a fuel cell unit being arranged on at least two branches of the line branch. The fluid supply line transporting the oxidant can supply the fuel cell unit in parallel, serially, or independently for each fuel cell unit. In particular, the lambda sensors are provided to enable the determination of a fuel cell unit-specific operating parameter. Preferably, a fuel cell unit-specific operating parameter is controlled via a fuel cell unit-specific flow control unit. Alternatively, each branch of the line branch has a fluid control unit for fuel cell unit-specific control of the fuel quantity.It is also conceivable that a lambda probe is arranged after at least two series-connected fuel cell units to determine a fuel cell unit-specific operating parameter. Due to the inventive design of the fuel cell device, inequalities in a fuel supply can advantageously be detected via the composition of the fluid exiting the respective fuel cell unit and compensated for by the control device.

[0017] Furthermore, it is proposed that the measuring unit be arranged in the flow direction of the exiting fluid immediately after an anode of a fuel cell unit of the fuel cell device. In this context, the term "immediately after" an object is understood to mean, in particular, that only fluid lines are arranged between the unit and the object. In particular, the composition of the fluid exiting the fuel cell device is maintained between the unit and the object. The inventive design of the fuel cell device advantageously allows the oxidation ratio of the fluid exiting the fuel cell device to be determined particularly reliably for determining the operating parameter.

[0018] It is further proposed that the measuring unit comprise at least one, in particular additional, lambda probe, in particular a broadband lambda probe, for detecting a recirculation flow. In particular, the measuring unit has at least two lambda probes. Preferably, a lambda probe is arranged in a flow direction of the fluid exiting the fuel cell device upstream of a line branch for recirculation. "Recirculation" is to be understood, in particular, as a merging of at least a portion of the fluid exiting a fuel cell unit with the fuel flowing to the fuel cell at a point upstream of the fuel cell. Preferably, the line branch has an adjustment unit, in particular a three-way valve, for adjusting the branching ratio of the fluid exiting the fuel cell unit at the line branch.In particular, the "recirculation flow" refers to the portion of the fluid exiting the fuel cell unit that is returned per unit of time. A lambda probe is preferably arranged downstream of the line branch for recirculating a portion of the fluid on a branch of the line branch, which branch is intended to discharge the fluid from the fuel cell device. In particular, the control device evaluates a measured value from the lambda probe arranged downstream of the line branch to control the operating parameter. The control device preferably determines the recirculation flow from a comparison of the oxidation ratios determined by the two lambda probes. The inventive design of the fuel cell device advantageously allows a recirculation flow to be detected. In particular, an operating parameter can advantageously be adjusted taking the recirculation flow into account.

[0019] The fuel cell control method according to the invention and / or the fuel cell device according to the invention should not be limited to the application and embodiment described above. In particular, the fuel cell control method according to the invention and / or the fuel cell device according to the invention can have a number of individual elements, components, units, and method steps that differs from the number stated herein in order to fulfill a functionality described herein. Furthermore, in the value ranges specified in this disclosure, values within the stated limits are also to be considered disclosed and can be used as desired. Drawings

[0020] Further advantages will become apparent from the following description of the drawings. The drawings illustrate three exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into further meaningful combinations.

[0021] They show: Fig. 1 is a schematic representation of a fuel cell device, Fig. 2 is a flow chart of a fuel cell control method according to the invention for the fuel cell device according to the invention, Fig. 3 is a schematic representation of a fuel cell device with recirculation of an anode outlet gas and Fig. 4 is a schematic representation of a fuel cell device according to the invention with fuel cell units connected in parallel. Description of the embodiments

[0022] Figure 1shows a fuel cell device 12a with at least one control device 18a for controlling an operating parameter, in particular fuel utilization. The fuel cell device 12a is preferably designed as a solid oxide fuel cell device. However, it is also conceivable for the fuel cell device 12a to have another configuration that would appear expedient to a person skilled in the art. The fuel cell device 12a preferably comprises a fuel cell unit 24a. The fuel cell unit 24a preferably comprises at least one fuel cell 30a with an anode 32a and a cathode 34a. The fuel cell unit 24a preferably comprises an anode inlet opening 36a and an anode outlet opening 38a for a fluid, in particular a fuel 40a. A fluid supply line 42a for transporting the fuel 40a into the anode 32a is preferably arranged at the anode inlet opening 36a.Preferably, a fluid discharge line 44a is arranged at the anode outlet opening 38a for transporting the fluid 14a produced in the anode 32a, in particular the at least partially oxidized fuel 40a, out of the anode 32a. Preferably, the fuel cell unit 24a comprises a cathode inlet opening 46a and a cathode outlet opening 48a for a fluid, in particular an oxidant 50a. Preferably, a fluid supply line 52a is arranged at the cathode inlet opening 46a for transporting the oxidant 50a into the cathode 34a. Preferably, a fluid discharge line 54a is arranged at the cathode outlet opening 48a for transporting the unused oxidant 50a out of the cathode 34a. The fuel cell device 12a preferably comprises a conversion unit 56a, in particular a reformer, for chemically converting a supplied fuel 40a. The conversion unit 56a is preferably arranged on the fluid supply line 42a to the anode 32a.Preferably, a fuel 40a is enriched with an oxidant and / or an oxidant carrier 16a prior to conversion by means of the conversion unit 56a. In particular, the fuel cell unit 24a has an oxidant carrier supply line 58a. Preferably, a fuel 40a is enriched with water. The oxidant carrier supply line 58a preferably has an evaporator 60a for generating water vapor.

[0023] The fuel cell device 12a comprises a measuring unit 20a for detecting a composition of a fluid 14a exiting the fuel cell device 12a, in particular anode outlet gas. The measuring unit 20a comprises at least one lambda probe 22a, in particular a broadband lambda probe. The measuring unit 20a is arranged in the flow direction of the exiting fluid 14a immediately downstream of an anode 32a of a fuel cell unit 24a of the fuel cell device 12a. The lambda probe 22a preferably has an internally sealed reference sample. However, it is also conceivable for the lambda probe 22a to compare an oxygen content of the fluid 14a exiting the anode outlet opening 38a with the oxygen content of the fluid located in the cathode-side fluid supply line 52a and / or fluid discharge line 54a. Alternatively, a fluid, in particular ambient air, supplied to the lambda probe 22a via a separate supply line is used as a reference sample.

[0024] The control device 18a preferably comprises a fluid control unit 62a, in particular a pump, a compressor and / or a valve, arranged on the anode-side fluid supply line 42a for adjusting and / or conveying a fuel quantity. The control device 18a preferably comprises a fluid control unit 64a, in particular a pump, a compressor and / or a valve, arranged on the cathode-side fluid supply line 52a for adjusting and / or conveying an oxidant quantity. The control device 18a preferably comprises, downstream of the cathode-side fluid control unit 64a, a measuring unit 66a for detecting the oxidant quantity flowing into the cathode 34a. The control device 18a preferably comprises a measuring unit 68a arranged on the oxidant carrier supply line 58a for detecting the oxidant carrier quantity.The control device 18a preferably comprises a current control unit 70a for adjusting and / or regulating the electrical current 74a flowing between the cathode 34a and the anode 32a. In particular, the current control unit 70a comprises a measuring unit 72a for detecting the electrical current 74a flowing between the cathode 34a and the anode 32a. The control device 18a preferably comprises a computing unit, in particular a central computing unit, for processing data detected by the measuring units 20a, 66a, 68a, 72a.

[0025] The fuel cell device 12a preferably has at least one connection unit 76a for tapping the electrical current 74a produced by the fuel cell unit 24a. Optionally, the fuel cell device 12a has a utilization unit 78a. The utilization unit 78a is preferably provided to utilize, in particular to oxidize, residues of oxidizable fuel 40a in the fluid 14a exiting the fuel cell device 12a. In particular, the utilization unit 78a has a burner unit 80a, which is fed by the cathode-side fluid discharge line 54a and the anode-side fluid discharge line 44a. The utilization unit 78a preferably has a heat exchanger 82a. The heat exchanger 82a is preferably provided to transfer heat generated by the burner unit 80a to a heat circuit 84a.Preferably, the heat circuit 84a is used to increase the temperature of the fluids located in the fluid supply lines 42a, 52a. Alternatively or additionally, the heat circuit 84a may have a circuit connection unit for dissipating the heat from the fuel cell device 12a, in particular for external reuse.

[0026] Figure 2shows a flowchart of a fuel cell control method 10a for controlling an operating parameter, in particular fuel utilization, of the fuel cell device 12a. In at least one method step, the operating parameter is controlled as a function of the composition of a fluid 14a exiting the fuel cell device 12a, in particular an anode outlet gas. Preferably, in at least one method step, measurement data collection and processing 86a takes place. In at least one method step, the exiting fluid 14a is evaluated with regard to a relative oxidant content, in particular oxygen content. In particular, an oxidation ratio of the fluid 14a exiting the fuel cell device 12a is recorded. In at least one method step, the supplied amount of an oxidant carrier 16a, in particular water, is recorded for controlling the operating parameter.Preferably, the amount of oxidant carrier supplied to the fuel 40a is detected. Preferably, an electric current 74a flowing between the cathode 34a and the anode 32a is detected. Preferably, the operating parameter, particularly fuel utilization, is deduced from at least the oxidation ratio, particularly by means of the computing unit. In particular, the operating parameter is determined taking into account the amount of oxidant carrier and the electric current 74a.

[0027] Preferably, in a further processing step 88a, a deviation of the operating parameter from a target value is detected. Preferably, in a further method step, a safety function is executed if a deviation of the operating parameter from a target value is detected. Preferably, the safety function checks termination criteria in the method step. In at least one method step, the safety function changes an operating mode of the fuel cell device 12a depending on a composition of the fluid 14a exiting the fuel cell device 12a. In particular, if a termination criterion is met, a shutdown 92a of the fuel cell device 12a, in particular of an individual fuel cell unit 24a, takes place.The safety function preferably checks at least whether the operating parameter exceeds a maximum permissible value and / or whether a manipulated variable for regulating the operating parameter has reached a limit of a provided value range. A check 90a by the safety function is preferably followed by a further method step in which an adjustment 94a of the supply parameters is carried out, in particular in a function as manipulated variables. In at least one method step, the composition of the fluid 14a exiting the fuel cell device 12a, in particular anode outlet gas, is used to adjust at least one supply parameter of the fuel cell device 12a, in particular a fuel quantity and / or an oxygen quantity. In particular, the deviation of the operating parameter from a target value is used to adjust the supply parameters.In particular, adjusting the supply parameters is intended to regulate the operating parameter, in particular to keep it constant. Preferably, the operating parameter is determined again after a change in at least one supply parameter.

[0028] In the Figures 3 and 4 Further embodiments are shown. The following descriptions and the drawings are essentially limited to the differences between the embodiments, whereby with regard to components with the same designation, in particular with regard to components with the same reference numerals, reference is also made to the drawings and / or the description of the other embodiments, in particular to the Figures 1 and 2 To distinguish the embodiments, the letter a is added to the reference numerals of the embodiment in the Figures 1 and 2 In the examples of the Figures 3 to 4the letter a is replaced by the letters b and c.

[0029] Figure 3 shows a fuel cell device 12b, in particular a solid oxide fuel cell device, with at least one control device 18b for controlling an operating parameter, in particular fuel utilization. The fuel cell device 12b comprises a measuring unit 20b for detecting a composition of a fluid 14b exiting the fuel cell device 12b, in particular anode outlet gas. The fuel cell device 12b preferably comprises a recirculation line 96b, in particular instead of the oxidant carrier supply line (cf. Fig.1, 58a). The measuring unit 20b comprises at least one, in particular additional, lambda probe 26b, in particular a broadband lambda probe, for detecting a recirculation flow 28b. A fluid control unit 98b, in particular a valve, a pump, or a compressor, is preferably arranged in the recirculation line 96b for adjusting the recirculation flow 28b. The recirculation line 96b preferably guides a portion of the fluid 14b' exiting the fuel cell unit 24b back into the anode-side fluid supply line 42b. In particular, the fluid discharge line 44b has a branch 100b at which the recirculation line 96b is closed. The returned portion is preferably combined with the fuel 40b at a point in the flow direction of the fuel 40b located in the fluid supply line 42b upstream of the conversion unit 56b. The lambda probe 22b is preferably arranged on a further branch of the branch 100b.In particular, the operating parameter is controlled by means of a measured value of the lambda probe 22b, which is arranged downstream of the branch 100b of the fluid discharge line 44b. For a description of a fuel cell control method 10b for the fuel cell control device 12b, please refer to the above description. Figure 2 of the analog fuel cell control method 10a. Preferably, during the measurement data acquisition and processing 86b of the fuel cell control method 10b, the supplied quantity of the oxidant carrier is not recorded.

[0030] Figure 4shows an embodiment of a fuel cell device 12c according to the invention, in particular a solid oxide fuel cell device, with at least one control device 18c for controlling an operating parameter, in particular fuel utilization. The fuel cell device 12c comprises a measuring unit 20c for detecting a composition of a fluid 14c, 14c' exiting the fuel cell device 12c, in particular anode outlet gas. The fuel cell device 12c comprises two fuel cell units 24c, 24c' connected in parallel. The fuel cell units 24c, 24c' are preferably connected in parallel with respect to a fuel supply to the anode 32c, 32c'. The fuel cell units 24c, 24c' are preferably connected in parallel with respect to an oxidant supply to the cathodes 34c, 34c'. The anodes 32c, 32c' are preferably fed by a common conversion unit 56c.Preferably, the fluids 14c, 14c' exiting the fuel cell units 24c, 24c' are combined in a common utilization unit 78c. It is also conceivable that a fuel cell unit-specific conversion unit and / or utilization unit is arranged in different branches of the fluid lines 42c', 42c", 44c', 44c". The measuring unit 20c comprises at least one lambda probe 22c, 22c', in particular one broadband lambda probe, for at least two parallel-connected fuel cell units 24c, 24c' of the fuel cell device 12c'. In particular, a fuel cell unit-specific operating parameter can be detected. With regard to a description of a fuel cell control method 10c for the fuel cell control device 12c, reference is made to the above description. Figure 2 of the analog fuel cell control method 10a.

Claims

1. Fuel cell control method for controlling an operating parameter, in particular fuel use, of a fuel cell device, in particular a solid oxide fuel cell device, characterized in that the fuel cell device comprises a measuring unit (20c) for detecting compositions of fluids (14c, 14c') exiting at least two fuel cell units (24c, 24c') connected in parallel, in particular anode discharge gases, wherein the measuring unit (20c) comprises in each case at least one lambda probe (22c, 22c'), in particular in each case one broadband lambda probe, for the at least two fuel cell units (24c, 24c') connected in parallel of the fuel cell device, wherein, in at least one method step, the operating parameter is controlled in a manner dependent on compositions of fluids (14c, 14c'), in particular anode discharge gases, exiting at least two fuel cell units (24c, 24c') connected in parallel.

2. Fuel cell control method according to Claim 1, <b>characterized in that, in at least one method step, the exiting fluid (14a; 14b; 14c) is evaluated with respect to a relative oxide content, in particular oxygen content.

3. Fuel cell control method according to Claim 1 or 2, <b>characterized in that, in at least one method step, the amount of an oxidizing agent carrier (16a; 16c), in particular water, which is fed in is detected in order to control the operating parameter.

4. Fuel cell control method according to one of the preceding claims, <b>characterized in that, in at least one method step, the composition of the fluid (14a; 14b; 14c) exiting the fuel cell device, in particular anode discharge gas, is used in order to set at least one supply parameter of the fuel cell device, in particular a fuel quantity and / or an oxygen quantity.

5. Fuel cell control method according to one of the preceding claims, <b>characterized in that, in at least one method step, an operating mode of the fuel cell device changes a safety function in a manner dependent on a composition of the fluid (14a; 14b; 14c) exiting the fuel cell device.

6. Fuel cell device, in particular solid oxide fuel cell device, with at least one control device (18a; 18b; 18c) for controlling an operating parameter, in particular fuel use, in particular by means of a fuel cell control method according to one of Claims 1 to 5, characterized by a measuring unit (20c) for detecting compositions of fluids (14c, 14c'), in particular anode discharge gases, exiting at least two fuel cell units (24c, 24c') connected in parallel, wherein the measuring unit (20c) comprises at least in each case one lambda probe (22c, 22c'), in particular in each case one broadband lambda probe, for the at least two fuel cell units (24c, 24c') connected in parallel of the fuel cell device.

7. Fuel cell device according to Claim 6, characterized in that the measuring unit (20a; 20b; 20c) is arranged immediately downstream of an anode (32a; 32b; 32c, 32c') of a fuel cell unit (24a; 24b; 24c, 24c') of the fuel cell device in the flow direction of the exiting fluid (14a; 14b; 14c).

8. Fuel cell device according to either of Claims 6 or 7, characterized in that the measuring unit (20b) comprises at least one, in particular additional, lambda probe (26b), in particular one broadband lambda probe, for detecting a recirculation current (28b).