Method for operating a fuel cell system

Abstract

The present invention relates to a method for operating, in particular for controlling and / or regulating a fuel cell system (100), in particular a solid oxide fuel cell system, comprising - having an anode path (10) ◯ an anode input (18) for receiving an anode input current (A in ) and ◯ an anode output (19) for outputting an anode output current (A out ), and ◯ a recirculation unit (19.1) for at least partially recirculating the anode output current (A out ) into the anode input current (A in ), comprising the method - receiving (110), by a control unit (FCCU), at least one controlled variable (CV), wherein the at least one controlled variable (CV) is specific for the anode path (10), - calculating (120), by the control unit (FCCU), at least one manipulated variable (MV) as a function of the at least one controlled variable (CV), - controlling (130), by the control unit (FCCU), the fuel cell system (100) as a function of the at least one manipulated variable (MV), whereupon the fuel cell system (100) is adjusted in order in particular to prevent fuel depletion of the fuel cell system (100).

Description

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

[0002] Fuel cell systems, in particular solid oxide fuel cells, are known, comprising at least one fuel cell unit having an anode and a cathode and an electrolyte located therebetween. A fuel gas, for example hydrogen or one comprising hydrogen (e.g. ammonia), can be supplied from the anode, and a further substance comprising oxygen, e.g. air, can be supplied from the cathode. The anode and cathode can be gas-permeable. The electrolyte represents an interface at which (separate) a reduction and an oxidation of a redox reaction take place. The redox reaction can comprise a reaction of oxygen with the fuel gas, e.g. hydrogen. There may be an excess of oxygen on the cathode side, while there may be a deficiency of oxygen on the anode side, since the oxygen reacts directly with hydrogen there. Due to electrical forces, oxygen diffuses from the cathode to the anode.Since the electrolyte in between is only permeable to oxygen ions, the oxygen absorbs electrons there. The resulting oxygen ions react with hydrogen ions on the anode side, which release electrons. During the exothermic reaction, an electron flow between the anode and cathode can be used externally as electrical power (current and / or voltage). Furthermore, fuel cell systems can comprise a stack of the fuel cell units described above.

[0003] However, devices and methods known from the prior art have disadvantages. For example, the electrical and / or thermal output as well as the efficiency can be optimized. In particular, the fuel utilization of the fuel cell system (e.g., relative to the overall system) and / or the fuel utilization of a fuel cell unit (of the fuel cell system, in particular relative to just the fuel cell unit, e.g., stack) may be inadequate. Furthermore, fuel depletion may occur at the anode, in particular, there may be too little fuel, for example, natural gas, and thus in particular hydrogen, to enable a (degradation-free and / or efficient) reaction. This may also be due to inadequate control and / or regulation of the fuel cell system.Deposits, particularly carbon deposits, resulting from the fuel can impact performance, longevity, and / or trouble-free operation. Furthermore, diffusion losses and / or polarization losses can impact performance, efficiency, costs, longevity, and / or trouble-free operation. The cell voltage, particularly the Nernst voltage, may be insufficient, which can particularly reduce the performance of a cell or stack. The control and / or regulation of known devices may be insufficient. The control and / or regulation of the fuel cell system may be (correspondingly) optimizable. In particular, it may be the case that during control and / or regulation, the fuel cell system calculates and / or sets, in particular, manipulated variables that are not adjustable and / or that may damage the fuel cell system.This can cause damage to a (post-)burner, for example at the anode outlet, especially if changes are made too quickly.

[0004] It is therefore an object of the present invention to at least partially overcome at least one of the disadvantages described above. In particular, it is an object of the invention to provide an optimized fuel cell system and a method which optimize performance, efficiency, longevity, freedom from faults and / or costs. In particular, it can be an object to prevent fuel depletion, in particular at the anode, and / or to reduce the likelihood of this occurring. In particular, it can be an object to improve the fuel utilization of the fuel cell unit, to save fuel and / or (in particular thereby) to prevent and / or reduce damage to the fuel cell system, e.g. to the burner.

[0005] The above object is achieved by a method having the features of the independent method claim, a fuel cell system having the features of the independent device claim, a computer program product having the features of the independent patent claim relating to a computer program product, a computer-readable data carrier having the features of the independent patent claim relating to a computer-readable data carrier, a control unit having the features of the independent patent claim relating to a control unit, and a system having the features of the independent patent claim relating to a system. Further features and details of the invention emerge from the subclaims, 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 with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other. In particular, advantages described in the context of the first, second, third, fourth, fifth and / or sixth aspect also apply to the first, second, third, fourth, fifth and / or sixth aspect.

[0006] The above object is achieved according to a first aspect by a method for operating, in particular for controlling and / or regulating a fuel cell system, in particular a solid oxide fuel cell system, comprising - having an anode path ◯ an anode input for receiving an anode input current and ◯ an anode output for outputting an anode output current, and ◯ a recirculation unit for at least partially returning the anode output stream to the anode input stream, in particular a recirculating volume flow, the method comprising - receiving, by a control unit, at least one controlled variable, wherein the at least one controlled variable is specific to the anode path, - Calculating, by the control unit, at least one manipulated variable as a function of the at least one controlled variable, - Controlling, by the control unit, the fuel cell system as a function of the at least one manipulated variable, whereupon the fuel cell system is adjusted in order in particular to prevent fuel depletion of the fuel cell system.

[0007] In this case, operation can in particular comprise controlling and / or regulating, wherein preferably a control unit (see below) is used. The described actions or features of the method can be carried out in the order shown and in particular can be carried out repeatedly. Preferably, the method can be used to control and / or regulate a fuel cell system according to the second aspect. In this case, a control unit according to the fifth aspect can particularly preferably be used for controlling and / or regulating. In this case, the control unit can carry out the corresponding actions or features and / or carry out a control, in particular where technically expedient, in order to preferably implement the actions.

[0008] The receipt of at least one controlled variable (CV) can be performed or carried out by the control unit, in particular by loading from a memory, a specification of a system connected to the fuel cell system, and / or a user input from a user of the fuel cell system. The at least one controlled variable can be specific to the anode path, the anode input current (e.g., before or near the anode input), and / or the anode output current (e.g., after or near the anode output).

[0009] Within the scope of the invention, it may be advantageous for the at least one controlled variable to have an (actual) oxygen-carbon ratio at the anode inlet and / or an (actual) proportion of hydrogen at the anode outlet.

[0010] Preferably, a (target) oxygen-carbon ratio and / or a (target) proportion of hydrogen at the anode outlet can be specified (as or for the controlled variable and / or), for example by corresponding setpoints. In other words, the control unit can set and / or change the at least one controlled variable, preferably by controlling it with the at least one manipulated variable. Advantageously, fuel depletion of the fuel cell system, in particular in the fuel unit, preferably at the anode, can be prevented and / or reduced. Furthermore, this can advantageously be used to improve the efficiency and / or performance of the fuel cell unit and / or the fuel cell system. Alternatively or additionally, FU Sys be used as a controlled variable. FU Sysand the proportion of hydrogen at the anode outlet (as control variables) achieve similar results. If pure hydrogen is used as fuel and / or no condensation is present, the following applies: FUSys=1−xH2,An,Out

[0011] The at least one manipulated variable can preferably be configured such that it is adjustable and / or does not lie in a (calculated) range that cannot be adjusted by the fuel cell system and / or could damage the fuel cell system.

[0012] The control can comprise controlling the anode path, in particular a fuel mass flow controller, a recirculation unit, a burner, and / or a recirculation fan of the anode path. Preferably, a (specific) operating point or (set) point of the fuel cell system can be set by the control, for example by adjusting parameters or manipulated variables, such as the recirculating volume flow and / or the fuel volume flow.

[0013] Within the scope of the invention, it is conceivable that the at least one manipulated variable comprises a volume flow of fuel, for example natural gas, and / or a recirculating volume flow, wherein in particular the recirculating volume flow is designed to adjust the at least partial return of the anode output flow into the anode input flow, in particular a recirculating volume flow, via the recirculation unit, wherein preferably the recirculating volume flow is calculated as a function of the volume flow of fuel.

[0014] Within the scope of the invention, volume flow and volumetric flow can be used interchangeably. These can, in particular, refer to a volume or a quantity per unit of time.

[0015] The at least one control variable can alternatively or additionally comprise a (temporal) rate of change of the recirculating volume flow and / or a (temporal) rate of change of the volume flow of fuel. Within the scope of the invention, a rate of change can (in principle) be a time derivative (ddt) of the corresponding size. Within the scope of the invention, a size indexed with #1 or #2 can (in principle) have a (more precisely) specified and / or a readjusted size, for example, the rate limiter (see below) can be set up to determine a first size, e.g., a minimum / maximum rate of change of the volume flow of fuel ddtV˙NG,Min / Max, by specifying a second quantity, e.g., a first rate of change of the volume flow of fuel ddtV˙NG,Min / Max,#1 is provided. This can be provided analogously for other variables. Preferably, within the scope of the invention, "Min / Max" can (in principle) have the minimum / maximum, i.e., in particular, the minimum and maximum value. Alternatively, this can also include a range between (and including) the minimum and maximum value. Preferably, within the scope of the invention, minimum / maximum values ​​can (in principle) be used by the control unit to limit the value, in particular by (improved) control, for example, ddtV˙NG,Min / Max, i.e. the minimum and / or maximum rate of change of the volume flow of fuel, can be used to determine the rate of change ddtV˙NG of the volume flow of fuel if the minimum rate of change is undershot and / or the maximum rate of change is exceeded.

[0016] The fuel flow rate can be adjusted by a fuel mass flow controller, which is controlled in particular by the control unit (e.g., via a data connection), thereby adjusting the fuel mass flow controller or an actuator of the fuel mass flow controller. This allows the fuel flow rate to be manipulated and / or adjusted as a manipulated value (MV).

[0017] The recirculating volume flow can be adjusted by a recirculation fan, which is controlled in particular by the control unit (e.g. via a data connection), whereby the recirculation fan or an actuator of the recirculation fan is adjusted. As a result, the recirculating volume flow can be manipulated as a control variable (“manipulated value”, MV) and / or adjusted. In other words, the quantity or volume flow can be adjusted, for example at the level of the recirculation fan. The recirculating volume flow can be configured as a function of the volume flow of fuel and / or the returned volume flow; in particular, the recirculating volume flow can be calculated from the sum of the volume flow of fuel and the returned volume flow, e.g. by the control unit.By adjusting the recirculating volume flow, fuel depletion of the fuel cell system, in particular the fuel cell unit, can be prevented and / or reduced.

[0018] It can be provided within the scope of the invention that the receiving, by a control unit, comprises receiving at least one disturbance variable, in particular comprising a current, a temperature of the fuel cell unit and / or a proportion of fuel in the anode input current, wherein the calculation, by the control unit, of at least one manipulated variable is carried out as a function of the at least one disturbance variable.

[0019] The temperature of the fuel cell unit can be measured in particular by a temperature sensor on the fuel cell unit and / or in or at the anode outlet.

[0020] The proportion of fuel in the anode input stream can in particular comprise the proportion of fuel, e.g., natural gas, in the anode path, in particular in the anode input stream, preferably at a location upstream of the anode path connection point, e.g., at the level of the fuel mass flow controller.

[0021] It is further conceivable that the receiving by the control unit comprises - Measuring, by a first lambda sensor, a first measurement signal which is specific for an oxygen-carbon ratio at the anode inlet, - Measuring, by a second lambda sensor, a second measurement signal which is specific for a proportion of hydrogen at the anode outlet, - Calculating the oxygen-carbon ratio at the anode inlet depending on the first measurement signal, - Calculating the proportion of hydrogen at the anode output depending on the second measurement signal.

[0022] It is also conceivable that the receiving, calculating and / or controlling is carried out by the control unit, in particular by a (first) control circuit of the control unit, comprising - a (first) feed-forward control for pre-control, which is set up to ◯ to provide a first control component for the volume flow of fuel, - a (first) closed-loop control, which is set up ◯ to provide a second control component for the volume flow of fuel and a third control component for the volume flow of fuel, - wherein the control unit is configured to provide the at least one manipulated variable, in particular a volume flow of fuel, as a function of the first control component, second control component and third control component for the volume flow of fuel, in particular by calculation by the control unit (e.g. a combination unit), for example by

[0023] Formation of an (arithmetic) sum of the first, second and / or third control components for the volume flow of fuel.

[0024] It can be provided that the feed-forward control, particularly compared to the closed-loop control, is prioritized (e.g., given greater weight) and / or used earlier in the control and / or regulation process. Furthermore, the P controller can be prioritized (e.g., given greater weight) in the control and / or regulation process, particularly compared to the I controller. Preferably, the feed-forward control can be used (first), followed by the P controller, and finally the I controller.

[0025] The feed-forward control, the closed-loop control, the P-controller and / or the I-controller can be implemented in (within) and / or by the control unit, in particular a (first and / or second) control loop, and / or have (or represent) (separate) control loops, in particular sub-control loops.

[0026] A minimum / maximum volume flow of fuel and / or recirculating volume flow can be the minimum / maximum volume flow for optimized operation. The fuel cell system can preferably be adjusted by control, so that a volume flow of fuel and / or recirculating volume flow advantageously lies between a minimum and maximum volume flow of fuel and / or minimum and maximum recirculating volume flow. In other words, the volume flow of fuel can preferably lie within a range for the volume flow of fuel. In other words, the recirculating volume flow can preferably lie within a range for the recirculating volume flow.

[0027] A minimum / maximum rate of change for the volume flow of fuel and / or the recirculating volume flow can be the minimum / maximum rate of change for optimized operation. The fuel cell system can preferably be adjusted by control, so that a rate of change for the volume flow of fuel and / or recirculating volume flow advantageously lies between a minimum and maximum rate of change for the volume flow of fuel and / or minimum and maximum rate of change for the recirculating volume flow. In other words, the rate of change for the volume flow of fuel can preferably lie within a range for the rate of change of the volume flow of fuel. In other words, the rate of change for the recirculating volume flow can preferably lie within a range for the rate of change of the recirculating volume flow.

[0028] The control unit, in particular a (first) control loop (e.g. as a control loop for x H2,An,out ), be designed to adjust the proportion of hydrogen at the anode outlet (see in particular Fig. 4 for the following explanations).

[0029] The fuel flow rate can be determined or calculated by the control unit, in particular by the feed-forward control, the P controller, and / or the I controller, depending on the first control component, second control component, and third control component for the fuel flow rate. In particular, the setpoint value and / or the control variable (CV) can be specified as or for the following: - x H2,An,out,sp

[0030] In particular, the following can be specified and / or measured (sensorily) as a measured variable (e.g. actual value): - x H2,An,out

[0031] In particular, the following can be specified as disturbance variables (DV) and / or measured (sensorily): - I, or i Stk - t Stk

[0032] This can i Stk to the control unit, in particular to calculate a minimum / maximum volume flow of fuel based on this, which is transmitted to the feed-forward control.

[0033] In particular, the following can be specified and / or calculated as manipulated variables (MV) (particularly as output): - V NG,ffc - V NG,P-Part - V NG,I-Part - V NG , in particular calculated as a function of V̇ NG,ffc, V NG,P-Part , and V̇ NG,I-Part , preferably by transmitting to and forming an (arithmetic) sum by a combination unit

[0034] The remaining (unlisted parameters), especially internal (in the control unit), may contain parameters or manipulated variables.

[0035] The control unit, in particular the feed-forward control, can receive at least one, preferably all, of the following values ​​(in particular as inputs) - i Stk - x H2,An,out,sp - x i,NG - t Stk - ddtV˙NG,Min / Max - FU Sys,Min / Max

[0036] The control unit, in particular the feed-forward control, can calculate and / or provide at least one, preferably all, of the following values ​​(in particular as outputs) - V NG,ffc , in particular transmitted to a combination unit, - V NG,Min / Max,#1 , in particular transmitted to the P-controller, - ddtV˙NG,Min / Max,#1, in particular transmitted to the P-controller,

[0037] The control unit, in particular the closed-loop control, preferably the P-controller, can receive at least one, preferably all, of the following values ​​(in particular as inputs) - V NG,Min / Max,#1 , in particular transmitted by feed-forward control, - ddtV˙NG,Min / Max,#1, in particular transmitted by feed-forward control - x H2,An,out,sp - x H2,An,out

[0038] The control unit, in particular the closed-loop control, preferably the P controller, can calculate and / or provide at least one, preferably all, of the following values ​​(in particular as outputs) - V NG,P-Part , in particular transmitted to a combination unit, - V NG,Min / Max,#2 , in particular transmitted to the I-controller, - ddtV˙NG,Min / Max,#2, in particular transmitted to the I controller.

[0039] The control unit, in particular the closed-loop control, preferably the I-controller, can receive at least one, preferably all, of the following values ​​(in particular as inputs) - V NG‚Min / Max,#2 , in particular transmitted by the P-controller, - ddtV˙NG,Min / Max,#2, in particular transmitted by the P-controller - x H2,An,out,sp - x H2,An,out

[0040] The control unit, in particular the closed-loop control, preferably the I controller, can calculate and / or provide at least one, preferably all, of the following values ​​(in particular as outputs) - V NG,I-Part , in particular transmitted to a combination unit

[0041] The feed-forward control can be designed as follows (see in particular Fig. 6 for the following explanations).

[0042] The feed-forward control can, in particular in a cascaded manner, have at least one of the following features: - an ipm module (ipm, “inversion of physical model”, see below), - a rate limiter (ratelim) and / or - value limiter (vallim)

[0043] The ipm module can be configured to at least partially calculate an operating point, in particular depending on a (reference) operating point of an adaptation (see below) and / or a reference measurement (or calibration, e.g. during commissioning).

[0044] The ipm module can be configured to receive (inputs), in particular from the control unit: - i Stk - x H2,An,out,sp - t Stk - x i,NG , and / or

[0045] The ipm module can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V NG,ffc , which is provided in particular to the rate limiter

[0046] The rate limiter (ratelim) can be set to limit the rate of change of the first control component for the volume flow of fuel ddtV˙NG,ƒcc which is smaller / larger than the minimum / maximum rate of change of the volume flow of fuel.

[0047] The rate limiter can be set up to receive (inputs), especially from the control unit: - ddtV˙NG,Min / Max and / or - V NG,ffc , in particular provided by the ipm module.

[0048] The rate limiter can be configured to calculate and / or provide (outputs) in particular depending on at least one input: - V NG,ffc , which is provided (modified or limited) to the value limiter and / or passed through (in particular passed on unchanged) - ddtV˙NG,Min / Max,#1, in particular an update or specification of ddtV˙NG,Min / Max, advantageously by ddtV˙NG,ƒcc to limit

[0049] The update can preferably be calculated by: ddtV˙NG,Min / Max,#1=ddtV˙NG,Min / Max−ddtV˙NG,ƒcc, in particular ddtV˙NG,Min,#1=ddtV˙NG,Min−ddtV˙NG,ƒcc and / or ddtV˙NG,Max,#1=ddtV˙NG,Max−ddtV˙NG,ƒcc, where preferably - V̇ NG,ffca filtering, in particular low-pass filtering (first order), in order to advantageously prevent infinitely large values ​​(and a software problem, such as a crash, of the control unit). The time constant of the filtering or the filter can be greater than the loop time of the control unit and / or (much) less than the (average) time constant of an (expected) rate of change ddtV˙NG,ƒcc of the first control component for the volume flow of fuel.

[0050] The value limiter (vallim) can be configured to provide at least a first minimum / maximum fuel flow rate, particularly analogous to the rate limiter (which specifies or limits the rate of change). The value limiter can be configured to receive (inputs), particularly from the control unit: - V NG,Min / Max and / or - V NG,ffc, in particular provided by the rate limiter.

[0051] The value limiter can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V NG,ffc , which is provided (modified or limited) to the control unit and / or is looped through (in particular passed on unchanged) and / or - V NG,Min / Max,#1 , in particular comprising an update or a specification of V̇ NG,Min / Max , advantageously by - V̇ NG,ffc to limit.

[0052] The update can preferably be calculated by: V˙NG,Min / Max,#1=V˙NG,Min / Max−V˙NG,ƒcc, in particular V˙NG,Min,#1=V˙NG,Min−V˙NG,ƒcc and / or V˙NG,Max,#1=V˙NG,Max−V˙NG,ƒcc, where preferably - V̇ NG,ffca filtering, in particular low-pass filtering (first order), in order to advantageously prevent infinitely large values ​​(and a software problem, such as a crash, of the control unit). The time constant of the filtering or the filter can be greater than a loop time of the control unit and / or (much) less than the (average) time constant of an (expected) rate of change ddtV˙NG,ƒcc of the first control component for the volume flow of fuel.

[0053] V̇ NG,Min / Max , i.e. the minimum and / or maximum volume flow of fuel, can be used to calculate the volume flow of fuel V̇ NG , if the minimum fuel flow rate is undershot and / or the maximum fuel flow rate is exceeded. This can be done analogously for V̇ NG,Min / Max,#1 , V̇ NG,Min / Max,#2 , V̇ recy,Min / Max (around V̇ recy to limit), V̇ recy,Min / Max,#1 , and / or V̇ recy,Min / Max,#2apply (see below). "#1" and / or "#2" may each have more specific, concrete, accurate, and / or improved minimum and / or maximum values, enabling improved operation.

[0054] This can ddtV˙NG,Min / Max, i.e. the minimum and / or maximum rate of change of the volume flow of fuel, can be used to determine the rate of change ddtV˙NG of the fuel flow rate when the minimum change rate of the fuel flow rate is undershot and / or the maximum change rate of the fuel flow rate is exceeded. This can be done analogously for ddtV˙NG,Min / Max,#1,ddtV˙NG,Min / Max,#2,ddtV˙recy,Min / Max (around ddtV˙recy to limit), ddtV˙recy,Min / Max,#1, and / or ddtV˙recy,Min / Max,#2, apply (see below). "#1" and / or "#2" may each have more specific, concrete, accurate, and / or improved minimum and / or maximum values, enabling improved operation.

[0055] Within the scope of the invention, it is optionally possible that the receiving, calculating and / or controlling is carried out by the control unit, in particular by a (second) control circuit of the control unit, comprising - a (second) feed-forward control for pre-control, which is set up ◯ to provide a first control component for the recirculating volume flow, - a (second) closed-loop control, which is set up ◯ to provide a second control component for the recirculating volume flow and / or a third control component for the recirculating volume flow, - wherein the control unit is configured to provide the at least one manipulated variable, in particular a recirculating volume flow, as a function of the first control component, second control component and third control component for the recirculating volume flow, in particular by calculation by the control unit (e.g. a combination unit), for example by forming an (arithmetic) sum of the first, second and / or third control component for the recirculating volume flow.

[0056] The control unit, in particular a (second) control loop (e.g. as a control loop for OC An,in ), be designed to adjust the oxygen-carbon ratio at the anode inlet (see in particular Fig. 10 for the following explanations).

[0057] The recirculating volume flow can be determined or calculated by the control unit, in particular by the feed-forward control, the P controller, and / or the I controller, depending on the first control component, second control component, and third control component for the recirculating volume flow. The following can be specified, in particular as a setpoint and / or (as or for the) controlled variable (CV): - OC An,in,sp

[0058] In particular, the following can be specified and / or measured (sensorily) as a measured variable (e.g. actual value): - OC An,in

[0059] The following can be calculated and / or apply (equation 1): OCAn,in=OCNG+r∗iStk∗nCells∗VNorm∗602∗F∗V˙NG∗∑IXi,NG∗KiC

[0060] The recirculation rate r can be calculable and / or defined (equation 2): r=V˙recy−V˙NGV˙recy+V˙NG∗KΔAn

[0061] The following table shows examples for different fuel (molecules), K C,i , and K ΔAn : Mole-kül, i K H2,i ΔK i Reaktion K C,i K ΔAn CH4 2 3 CH4 + H2O →3H2+CO 1 2 C2H6 3 5 C2H6 + 2H2O →5H2+2CO 2 4 C3H8 4 7 C3H8 + 3H2O - 7H2+3CO 3 6 C4H 10 5 9 C4H 10 + 4H2O →9H2+4CO 4 8 CO2 0 0 - 1 0 O2 0 0 - 0 0 N2 0 0 - 0 0 H2 2 0 - 0 0

[0062] K can H2,i the number of pseudo-H2 molecules. ΔK i exhibit an increase in the molar amount (or volume flow) due to the reaction, especially from the perspective of the fuel cell system. K C,i the number of carbon atoms in the molecule. K ΔAn exhibit an increase in the molar quantity (or volume flow) due to the reaction, particularly from the perspective of the anode or the fuel cell unit.

[0063] The following can apply (equation 3): KΔAn=∑ixi,NG∗KiC

[0064] Which, in particular from equations 2, 3 and 4, can result in (equation 4): OCAn,in−OCNG=+(V˙recy−V˙NG)∗iStk∗nCells∗VNorm∗60V˙recy+V˙NG∗(∑Ixi,NG∗KiC)∗2∗F∗V˙NG∗∑Ixi,NG∗KiC

[0065] This can result, in particular starting from equation 4, in (equation 5): V˙recy=(OCAn,in,sp−OCNG)∗V˙2NG)∗∑Ixi,NG∗KiC∗2∗F∗∑Ixi,NG∗KiC+V˙NG∗iStk∗nC ells∗VNorm∗60iStk∗nCells∗VNorm∗60−(OCAn,in,sp−OCNG)∗2∗F∗V˙NG∗∑Ixi,NG∗KiC

[0066] In particular, the following can be specified as disturbance variables (DV) and / or measured (sensorily): - I, or i Stk

[0067] In particular, the following can be specified and / or calculated as manipulated variables (MV) (particularly as output): - V recy,ffc - V recy,P-Part - V recy,I-Part - V recy , in particular calculated as a function of V̇ recy,ffc , V̇ recy,P-Part , and V̇ recy,I-Part , preferably by transmitting to and forming an (arithmetic) sum by a combination unit

[0068] The remaining (unlisted parameters), especially internal (in the control unit), may contain parameters or manipulated variables.

[0069] The control unit, in particular the feed-forward control, can receive at least one, preferably all, of the following values ​​(in particular as inputs) - V NG , in particular transmitted by the (first) control loop (output, see above) - V recy,Min / Max - i Stk - OC An,in,sp - x i,NG - ddtV˙recy,Min / Max

[0070] The control unit, in particular the feed-forward control, can calculate and / or provide at least one, preferably all, of the following values ​​(in particular as outputs) - V recy,ffc , in particular transmitted to a combination unit, - V recy,Min / Max,#1 , in particular transmitted to the P-controller, - ddtV˙recy,Min / Max,#1, in particular transmitted to the P-controller,

[0071] The control unit, in particular the closed-loop control, preferably the P-controller, can receive at least one, preferably all, of the following values ​​(in particular as inputs) - V recy,Min / Max,#1 , in particular transmitted by feed-forward control, - ddtV˙recy,Min / Max,#1, in particular transmitted by feed-forward control - OC An,in,sp - OC An,in

[0072] The control unit, in particular the closed-loop control, preferably the P controller, can calculate and / or provide at least one, preferably all, of the following values ​​(in particular as outputs) - V recy,P-Part , in particular transmitted to a combination unit, - V recy,Min / Max,#2 , in particular transmitted to the I-controller, - ddtV˙recy,Min / Max,#2, in particular transmitted to the I-controller. The control unit, in particular the closed-loop control, preferably the I-controller, can receive at least one, preferably all, of the following values ​​(in particular as inputs) - V recy,Min / Max , #2 , in particular transmitted by the P-controller, - ddtV˙recy,Min / Max,#2, in particular transmitted by the P-controller - OC An,in,sp - OC An,in

[0073] The control unit, in particular the closed-loop control, preferably the I controller, can calculate and / or provide at least one, preferably all, of the following values ​​(in particular as outputs) - V recy,I-Part , in particular transmitted to a combination unit.

[0074] The feed-forward control can be designed as follows (see in particular Fig. 11 for the following explanations).

[0075] The feed-forward control can, in particular in a cascaded manner, have at least one of the following features: - an ipm module (ipm, “inversion of physical model”, see below), - a rate limiter (ratelim) and / or - value limiter (vallim)

[0076] The ipm module can be configured to at least partially calculate an operating point, in particular depending on a (reference) operating point of a reference measurement (or calibration, e.g. during commissioning).

[0077] The ipm module can be configured to receive (inputs), in particular from the control unit: - i Stk - OC An,in,sp - V NG,ffc , and / or - x i,NG

[0078] The ipm module can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V recy,ffc , which is provided in particular to the rate limiter.

[0079] The rate limiter (ratelim) can be set to limit the rate of change of the first control component for the recirculating volume flow ddtV˙recy,ƒcc which is smaller / larger than the minimum / maximum rate of change ddtV˙recy,Min / Max the recirculating volume flow must be blocked and / or limited.

[0080] The rate limiter can be set up to receive (inputs), especially from the control unit: - ddtV˙recy,Min / Max and / or - V recy,ffc , in particular provided by the ipm module.

[0081] The rate limiter can be configured to calculate and / or provide (outputs) in particular depending on at least one input: - V recy,ffc , which is provided (modified or limited) to the value limiter and / or passed through (in particular passed on unchanged) −ddtV˙recy,Min / Max,#1, in particular an update or specification of ddtV˙recy,Min / Max, advantageously by ddtV˙recy,ƒcc V recy,fcc to limit

[0082] The update can preferably be calculated by: ddtV˙recy,Min / Max,#1=ddtV˙recy,Min / Max−ddtV˙recy,ƒcc, in particular ddtV˙recy,Min,#1=ddtV˙recy,Min−ddtV˙recy,ƒcc and / or ddtV˙recy,Max,#1=ddtV˙recy,Max−ddtV˙recy,ƒcc, where preferably V̇ recy,ffca filtering, in particular low-pass filtering (first order), in order to advantageously prevent infinitely large values ​​(and a software problem, such as a crash, of the control unit). The time constant of the filtering or the filter can be greater than the loop time of the control unit and / or (much) less than the (average) time constant of an (expected) rate of change ddtV˙recy,ƒcc of the first control component for the recirculating volume flow.

[0083] The value limiter (vallim) can be configured to provide at least a first minimum / maximum recirculating volume flow, in particular analogous to the rate limiter (which specifies or limits the rate of change).

[0084] The value limiter can be set up to receive, in particular from the control unit, the following inputs: - V recy,Min / Max and / or - V recy,ffc, in particular provided by the rate limiter.

[0085] The value limiter can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V recy,ffc , which is provided (modified or limited) to the control unit and / or is looped through (in particular passed on unchanged) and / or - V recy,Min / Max,#1 , in particular comprising an update or a specification of V̇ recy,Min / Max , advantageously by V̇ recy,ffc to limit.

[0086] The update can preferably be calculated by: V˙recy,Min / Max,#1=V˙recy,Min / Max−V˙recy,ƒcc, in particular V˙recy,Min,#1=V˙recy,Min−V˙recy,ƒcc and / or V˙recy,Max,#1=V˙recy,Max−V˙recy,ƒcc, where preferably V̇ recy,ffca filtering, in particular low-pass filtering (first order), in order to advantageously prevent infinitely large values ​​(and a software problem, such as a crash, of the control unit). The time constant of the filtering or the filter can be greater than a loop time of the control unit and / or (much) less than the (average) time constant of an (expected) rate of change ddtV˙recy,ƒcc of the first control component for the recirculating volume flow.

[0087] The remaining components of the control loop, in particular the P controller and / or the I controller, can be designed identically or analogously to the P controller and / or I controller shown below (in particular as in the closed-loop control).

[0088] Furthermore, it can be provided within the scope of the invention that the closed-loop control has - a P-controller (P-part) which is designed to ◯ to provide a second control component for the volume flow of fuel and / or ◯ to provide a second control component for the recirculating volume flow, - an I-controller (I-Part) which is set up to ◯ to provide a third control component for the volume flow of fuel and / or ◯ to provide a third control component for the recirculating volume flow.

[0089] The P controller and the I controller can together form a PI controller.

[0090] The closed-loop control, in particular the PI controller or P controller, can be designed as follows (see in particular Fig. 8 for the following explanations).

[0091] This can have, in particular in a cascaded manner, at least one of the following features: - a P-controller (P-Part), - a rate limiter (ratelim) and / or - a value limiter (vallim)

[0092] The P-controller can be set up to receive (inputs), in particular from the control unit: - x H2,An,out,sp and / or - x H2,An,out

[0093] The P-controller can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V NG,P-Part , in particular a second control component for the volume flow of fuel, which is provided in particular to the rate limiter.

[0094] The rate limiter (ratelim) can be set up to limit the rate of change of the second control component V̇ NG,P-Part for the volume flow of fuel which is smaller / larger than the first minimum / maximum rate of change ddtV˙NG,Min / Max,#1 The fuel flow rate must be blocked and / or limited. The rate limiter can be configured to receive the following inputs, particularly from the control unit: −ddtV˙NG,Min / Max,#1 and / or - V NG,P-Part , in particular provided by the P controller.

[0095] The rate limiter can be configured to calculate and / or provide (outputs) in particular depending on at least one input: - V NG,P-Part , which is provided (modified or limited) to the value limiter and / or passed through (in particular passed on unchanged) - ddtV˙NG,Min / Max,#2, in particular an update or specification of ddtV˙NG,Min / Max,#1, advantageously by ddtV˙NG,P−Part (improved) to limit.

[0096] The update can preferably be calculated by: ddtV˙NG,Min / Max,#2=ddtV˙NG,Min / Max,#1−ddtV˙NG,P−Part, in particular ddtV˙NG,Min,#2=ddtV˙NG,Min,#1−ddtV˙NG,P−Part and / or ddtV˙NG,Max,#2=ddtV˙NG,Max,#1−ddtV˙NG,P−Part, where preferably V̇ NG,P-Part a filtering, in particular low-pass filtering (first order), in order to advantageously prevent infinitely large values ​​(and a software problem, such as a crash, of the control unit). The time constant of the filtering or the filter can be greater than the loop time of the control unit and / or (much) less than the (average) time constant of an (expected) rate of change ddtV˙NG,P−Part of the second control component for the volume flow of fuel.

[0097] The value limiter (vallim) can be configured to provide at least a second minimum / maximum volume flow of fuel, in particular analogous to the rate limiter (which specifies or limits the rate of change).

[0098] The value limiter can be set up to receive, in particular from the control unit, the following inputs: - V NG,Min / Max,#1 and / or - V NG,P-Part , in particular provided by the rate limiter.

[0099] The value limiter can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V NG,P-Part , which is provided (modified or limited) to the control unit and / or is looped through (in particular passed on unchanged) and / or - V NG‚Min / Max,#2 , in particular comprising an update or a specification of V̇ NG,Min / Max,#1, advantageously by V̇ NG-P-Part (improved) to limit.

[0100] The update can preferably be calculated by: ddtV˙NG,Min / Max,#2=ddtV˙NG,Min / Max,#1−ddtV˙NG,P−Part

[0101] The following can preferably apply and / or be calculable: ddtV˙NG,P−Part=kp∗(xH2,An,out,sp−xH2,An,out)

[0102] In this case, k p include a (proportionality) constant, which can advantageously be used for (corresponding) control and / or regulation. For example, k p = [0,1 ; 8]. Where k p , especially in a first approximation, for example as a starting value of a control and / or regulation, have a coefficient which results from regression according to the ipm model, for example the following can apply: - k pcan be proportional to the (inverted) coefficient a2, especially for quadratic regression (e.g. a2 = -4.01109569), or - k p can be proportional to the (inverted) coefficient a3, especially for cubic regression (e.g. a3 = -4.93578404).

[0103] The closed-loop control, in particular the PI controller or I controller, can be designed as follows (see in particular Fig. 9 for the following explanations).

[0104] This can have, in particular in a cascaded manner, at least one of the following features: - an I-controller (I-part), - a rate limiter (ratelim) and / or - a value limiter (vallim)

[0105] The I-controller can be set up to receive (inputs), in particular from the control unit: - x H2,An,out,sp and / or - x H2,An,out

[0106] The I-controller can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V NG,I-Part , in particular a third control component for the volume flow of fuel, which is provided in particular to the rate limiter.

[0107] The rate limiter (ratelim) can be set to limit the rate of change of the third control component V̇ NG,I-Part for the volume flow of fuel which is smaller / larger than the first minimum / maximum rate of change ddtV˙NG,Min / Max,#1 The volume flow of fuel must be blocked and / or limited.

[0108] The rate limiter can be set up to receive (inputs), especially from the control unit: - ddtV˙NG,Min / Max,#1 and / or - V NG,P-Part , in particular provided by the I controller.

[0109] The rate limiter can be configured to calculate and / or provide (outputs) in particular depending on at least one input: - V NG,I-Part , which is provided (modified or limited) to the value limiter and / or passed through (in particular passed on unchanged).

[0110] The value limiter (vallim) can be set up to receive (inputs), especially from the control unit: - V NG,Min / Max,#1 and / or - V NG,I-Part , in particular provided by the rate limiter.

[0111] The value limiter can be configured to calculate and / or provide (outputs), in particular depending on at least one input: - V NG,I-Part , which is provided (modified or limited) to the control unit and / or passed through (in particular passed on unchanged).

[0112] The following can preferably apply and / or be calculable: ddtV˙NG,I−Part=∫tki∗(xH2,An,out,sp−xH2,An,out)dt

[0113] In this case, k i comprise a (proportionality) constant, which can advantageously be used for (corresponding) control and / or regulation.

[0114] With regard to the present invention, it is conceivable that the receiving, calculating and / or controlling by the control unit, by a control circuit of the control unit, comprises calculating a range of at least one manipulated variable which is designed to enable improved operation of the fuel cell system, wherein in particular the range comprises a minimum volume flow of fuel V̇ NG,Min and a maximum volume flow of fuel V̇ NG,Max has.

[0115] The range can encompass a range that (as a lower limit) ranges from the minimum fuel flow rate to (as an upper limit) the maximum fuel flow rate. In other words, this can encompass the permissible and / or optimized range for the fuel flow rate. For example, this range can be adjustable (at all), e.g., depending on the operating point, and / or enable damage-free or low-wear operation. The range can be relative to and / or specific to a specific operating point, in particular one set by control. Accordingly, it can be a relative range, which in particular is not specified absolutely. The following can apply to the range for the fuel flow rate: R=[V˙NG,Min,V˙NG,Max]

[0116] For example, this can Fig. 5 can be taken.

[0117] The minimum volume flow of fuel V̇ NG,Min or maximum volume flow of fuel V̇ NG,Max be calculable and / or defined by: V˙NG,Min=iStk∗nCellsF∗FUSys,Max∗VNorm∗SK V˙NG,Max=iStk∗nCellsF∗FUSys,Min∗VNorm∗SK

[0118] Accordingly, V̇ NG,Min can be calculated depending on the quantities on the right. Likewise, V̇ NG,Max be calculable depending on the quantities on the right. SK can have a scaling constant, which can be, for example, 60. Here, i Stk the power of a fuel cell unit or a (single) fuel cell, n Cells the number of fuel cells, F the Faraday constant, V Norm a standard volume, FU Sys,Min a minimum fuel utilization of the fuel cell system and / or FU Sys,Maxmaximum fuel utilization of the fuel cell system. The current I can be the product of i Stk and n Cells FU can Sys,Min / Max , in particular analogous to above, have a minimum / maximum fuel utilization of the fuel cell system, in particular the following can apply: FUSys,Min / Max=[FUSys,Min,FUSys,Max]or{FUSys,Min,FUSys,Max}

[0119] Within the scope of the invention, in particular also analogously for other quantities, the entire range limited by the minimum and maximum value or the minimum and maximum value themselves can be meant.

[0120] The method may include a start-up, which in particular comprises (beginning) operation, in particular control and / or regulation. In other words, it may be provided that the control unit, the control loop, the feedforward control, and / or the closed-loop control must be started and / or restarted, for example, due to a (software) crash, power failure, (initial) commissioning, and / or the like. In this case, it may preferably be provided that at least one manipulated variable is designed to be continuous and / or steady.

[0121] In principle, the ipm model can be provided, especially as input: - x H2,An,out and OC An,in , especially if the control unit is deactivated, - x H2,An,out,sp and OC An,in,sp , especially when the control unit is activated.

[0122] Preferably x H2,An,out and OC An,inbe filtered by a filter, in particular by a low-pass filter, preferably first order, in order to advantageously prevent unrealistic, non-adjustable and / or infinite values ​​or outputs of the ipm model.

[0123] In principle, the P controller, especially its output, can be set to 0 or reduced, especially if the control unit is deactivated. Once the control unit is activated, the described calculation can be performed.

[0124] In principle, the I controller, especially its output, can be set to the following value, especially if the control unit is deactivated: V˙NG,I−Part=V˙NG−V˙NG,ƒcc V˙recy,I−Part=V˙recy−V˙recy,ƒcc

[0125] V̇ NG and V̇ recy can be measured. V̇ NG,ffc and V̇ recy,ffcare calculated by the feed-forward control, which can preferably be stored in a memory of the I-controller, in particular for later retrieval. If the I-controller is deactivated, it can be provided that no calculation, in particular no integration, is carried out. It can (thereby) be provided that the calculated controlled variable is identical to the measured value(s) of the controlled variable when the I-controller is deactivated. As a result, a corresponding (controlled) actuator, for example the fuel mass flow controller and / or recirculation fan, can (always) receive a continuous or steady control value.

[0126] It may be provided that the P controller is set to zero, especially during a deactivated phase. In this case, the other and / or remaining (three) components can be summed, especially simultaneously.

[0127] Changes that can be set or specified when activating (in principle) Fig. 12. This allows a continuous or steady course or behavior to be achieved.

[0128] The feed-forward control can be provided (additionally), especially as inputs: - x H2,An,out - b act,Cont , in particular an activation signal for the control loop, which for example has a Boolean signal for activating the control loop.

[0129] The P-controller can be provided with (additional) inputs, especially: - b act,Cont

[0130] The I controller can be provided (additionally), especially as inputs: - b act,Cont - V NG,ffc

[0131] Adaptation (especially in Fig. 13), which can be carried out in particular during (first) commissioning and / or due to wear, in order to advantageously enable improved operation.

[0132] (Stationary) (actual) values ​​can be measured, in particular: - i Stk - x H2,An,out - OC An,in - V NG - V recy .

[0133] The adaptation can be performed or initialized by a dedicated adaptation unit of the control unit. During adaptation, a (repeated) comparison can be made between the manipulated variable and the corresponding measured (actual) values. The values ​​can be stored in a memory unit of the control unit. For example, they can be stored in look-up tables. This can be calculable and / or defined, particularly depending on i Stk ΔV˙NG,Adapt=V˙NG−V˙NG,ƒcc ΔV˙recy,Adapt=V˙recy−V˙recy,ƒcc

[0134] During (regular) operation, especially when no adaptation is performed, these values ​​can be accessed, for example, by loading them from memory. These can then be added (additively) to the corresponding blocks of the control loop. An example is shown in Fig. 13 shows an adaptation unit (Adapt), which is activated in particular by an activation signal b act,Adapt can be initialized for the adaptation unit, which, for example, has a Boolean signal to activate the adaptation. The adaptation unit can be provided with, in particular as inputs: - i Stk - V NG,ffc - b act,Adapt - V NG

[0135] The P-controller can be provided with, in particular as inputs: - b act,Cont

[0136] The adaptation unit can provide, in particular as output (e.g. to a combination unit): - V NG,Adapt

[0137] Analogous (especially to Fig. 13) the oxygen-carbon ratio can also be adapted.

[0138] The ipm module can have at least one of the following features, in particular to provide an output (e.g. V̇ NG,ffc ) to enable: - One-time calibration - chemical equilibrium estimation - Estimation via regression

[0139] One-time calibration (for example in Fig. 7) the setting of a plurality of operating points. It can be assumed that the fuel cell system is at a (constant or equal) temperature t Stkthe fuel cell unit. A reference gas (or natural gas) is used, and in particular, it is assumed that it has all possible concentrations. A 1D look-up table can be generated. A (fixed) hydrogen content can be assumed for each operating point. The operating points have (or are defined by) a (respective) current i Stk . The first control component - V̇ NG,ffc for the volume flow of fuel (in the look-up table) depending on the current i Stk be specified (see e.g. Fig. 7). Interpolation can be performed between neighboring points.

[0140] The chemical equilibrium estimation can include measuring and / or estimating the proportions (composition) of the fuel, e.g., natural gas (NG). This can be stored in the storage unit and / or specified to the control unit. Depending on the measurement and / or estimation, an H2 / C ratio can be calculated, in particular the ratio between hydrogen molecules and carbon in the fuel. For example, two H2 (pseudo) molecules can be provided, in particular bound, in one methane molecule CH4. At least one, preferably all, of the following assumptions can be used: 1) The hydrogen mole flow (preferred), the hydrogen mole fraction, and / or the mole hydrogen quantity is identical at the anode outlet and at the inlet of the burner, 2) The fuel cell unit is designed to completely convert or react all alkanes contained in the fuel, 3) Steam reforming only takes place upstream of and in the fuel cell unit, 4) All carbon atoms at the anode exit are oxidized by at least one oxygen atom, and / or 5) The distribution or reaction of the oxygen atom between or with the available reaction partners occurs according to the following rules: a. (H2 / C) / (1+H2 / C) of the oxygen atoms react with or bind to a hydrogen molecule, b. 1 / (1+H2 / C) of the oxygen atoms react with or bind to a carbon monoxide molecule.

[0141] Accordingly, it can be intended that (only) the following molecules are present at the anode output: - CO - CO2 - H2 - H2O

[0142] In particular, calculating a fuel volume flow can have an accuracy of approximately 10%, especially compared to the (actual) fuel volume flow. This can advantageously be compensated, in particular by using an oxygen sensor, which can advantageously provide more accurate measured values.

[0143] A volume flow at the inlet of the burner can be calculated and / or defined: V˙Tgb,in=V˙NG∗(1+∑xi,NG∗ΔKi)

[0144] A volume flow of all H2-containing molecules at the inlet of the burner can be calculated and / or defined: V˙H2−wiseTgb,in=V˙NG∗∑ixi,NG∗KH2,i

[0145] A volume flow of oxygen atoms which are bound by carbon atoms and / or react with them can be calculated and / or defined: V˙OinCO=V˙NG∗∑ixi,NG∗KC,i

[0146] A volume flow of oxygen atoms which are (still) bound by hydrogen molecules H2 or carbon monoxide molecules CO2 and / or can react with them can be calculated and / or defined: V˙H2O=(iStk∗nCells2∗F∗VNorm∗60−V˙OinCO)∗H2 / C1+H2 / C

[0147] A volume flow of water can be calculable and / or defined: V˙H2O=(iStk∗nCells2∗F∗VNorm∗60−V˙OinCO)∗H2 / C1+H2 / C

[0148] The volume flow of hydrogen entering the burner can be calculable and / or defined: V˙H2=V˙H2−wiseTgb,in−(iStk∗nCells2∗F∗VNorm∗60−V˙OinCO)∗H2 / C1+H2 / C

[0149] A (molar) proportion of hydrogen at the anode outlet can be calculable and / or defined: xH2,An,out=V˙H2−wiseTgb,in−(iStk∗nCells2∗F∗VNorm∗60−V˙OinCO)∗H2 / C1+H2 / CV˙Tgb,in

[0150] Transformed (by inserting see above) the following can apply: xH2,An,out==V˙NG∗∑Ixi,NG∗KH2,i−(iStk∗nCells2∗F∗VNorm ∗60−V˙NG∗∑Ixi,NG∗KC,i)∗H2 / C1+H2 / CV˙NG∗(1+∑xi,NG∗ΔKi)

[0151] Solving for V̇ NG can result in: V˙NG=−(iStk∗nCells2∗F∗VNorm∗60)∗H2 / C1+H2 / C(1+∑xi,NG∗ ΔKi)∗xH2,An,out−∑Ixi,NG∗KH2,i−∑Ixi,NG∗KC,i∗H2 / C1+H2 / C

[0152] Identical or analogous can - V̇ NG,ffc be predictable.

[0153] The regression estimation can be quadratic and / or cubic. This can be applied at chemical equilibrium. It can also be used for the following molecules (in the fuel): - CH4 - CO - CO2 - H2, and / or - H2O

[0154] It can be assumed that the temperature t Stkof the fuel cell unit is identical to the temperature of chemical equilibrium. It can be assumed that the H / C ratio of the fuel or molecules is known.

[0155] At least one, preferably all, of the following features can be implemented: - Calculate the oxygen-carbon ratio at the anode outlet OC An,out depending on x H2,An,out,sp , t Stk , and / or H / C NG Ratio of the fuel, in particular natural gas, and / or - Inverting the definition of the oxygen-carbon ratio at the anode outlet by the volume flow of fuel V̇ NG to obtain.

[0156] A quadratic regression (especially truncation after the fourth term) can be used: OCAn,out=a0+a1∗H / CNG+a2∗xH2,An,out,sp+a3H / CNG2+a4∗xH2,An,out,sp2

[0157] The following may apply: - a0 = 2.947916331 - a1 =0.139016503 - a2 = -4.01109569 - a3 = 0.033707367 - a4 = -0.41423938 and / or - R 2 = 0.982

[0158] This can have the advantage that OC An,out independent of t Stk can be calculated.

[0159] A cubic regression (especially stopping after the eleventh term) can be used: OCAn,out=a0+a1∗tStk+a2∗HCNG+a3∗xH2,An,out,sp+a4∗tStk∗xH2,An,out,sp+a5∗HCNG2+a6∗HCNG∗xH2,An ,out,sp+a7∗xH2,An,out,sp2+a8∗tStk∗∗xH2,An,out,sp2+a6∗HCNG∗xH2,An,out,sp2+a10∗xH2,An,out,sp2

[0160] The following may apply: - a0 = 3.169848530135616 - a1 = 9.45113e-05 - a2 = -0.049573017 - a3 = -4.93578404 - a4 = -0.00931842 - a5 = 0.038860973 - a3 = 1.446767671 - a7 = 5.066110715 - a3 = 0.039605113 - a9 = -5.35995891 - a 10 = -19.1204014 and / or - R 2 = 0.991

[0161] This can have the advantage that OC An,out independent of t Stk can be calculated.

[0162] Within the scope of the invention, the chemical equilibrium can (in principle) be calculated, particularly by a computer. For example, the Python module "Cantera" can be used for this purpose. The following values ​​can be used (as examples): - OC An,out = [3,4], and in particular 5 equidistant values ​​from this range - H / C = [3.5,4.5], and in particular 10 equidistant values ​​from this range - t Stk = [590°C, 630°C], and in particular 10 equidistant values ​​from this range.

[0163] The above object is achieved according to a second aspect by a fuel cell system according to the invention, in particular a solid oxide fuel cell system, comprising - having an anode path ◯ an anode input for receiving an anode input current and ◯ an anode output for outputting an anode output current, and ◯ a recirculation unit for at least partially returning the anode output current to the anode input current, - wherein the fuel cell system is configured to be controlled by a control unit, in particular according to the fifth aspect, in order to implement the method according to the first aspect, in particular to prevent fuel depletion of the fuel cell system.

[0164] The fuel cell unit can comprise one or more fuel cells, which can be arranged in a stack (e.g., a "stack"). Each fuel cell can comprise an anode and / or a cathode, with the anode being connected to the anode path and / or the cathode being connected to the cathode path. The fuel cell unit(s) can preferably comprise solid oxide fuel cells.

[0165] The fuel cell system or fuel cell unit can be used to generate energy, in particular by generating thermal and / or electrical energy or power. Thus, a current and / or voltage can be utilized, for example, for external devices. The fuel cell system preferably comprises an inverter, in particular a direct current / alternating current converter. This can preferably be tapped via an anode electrode connected to the anode, and a cathode electrode connected to the cathode. The inverter can be connected to the control unit, for example via a data connection, whereby the control unit can advantageously specify a (target) current to the inverter (e.g., by controlling it) and / or the inverter can transmit a, in particular measured, (actual) current to the control unit.

[0166] The anode path can carry a material flow (e.g., anode input current), in particular to an anode input (see below). The anode path can also, at least partially, comprise a material flow from the anode output. The anode path can carry the anode input current A in and / or anode output current A out include, in particular, lead.

[0167] The anode input current A in (essentially) include the material flow from a fuel tank (in particular inlet to the system) to an anode inlet.

[0168] The anode inlet can be configured to receive an anode input current and, in particular, to guide it into the interior of the fuel cell unit.

[0169] The anode outlet can be configured to output an anode output current, in particular from the interior of the fuel cell unit. The anode output current comprises at least partially water, in particular water vapor.

[0170] The fuel tank can comprise a container and / or a supply line. This allows fuel, in particular natural gas, methane, ammonia, and / or a chemical compound comprising hydrogen, to be provided. This can then be introduced into the anode path through the hydrogen tank.

[0171] A desulfurization unit can be arranged between the fuel tank and the fuel valve and / or connected to them. This can be used to enable desulfurization and / or (at least partial) removal of sulfur or sulfur compounds.

[0172] The fuel valve can be used for connecting and / or disconnecting, particularly between the fuel tank or desulfurization unit and the fuel mass flow controller. This allows adjustment of whether a medium (such as those mentioned above) can even enter the anode path.

[0173] The fuel mass flow controller can be used to set a volume flow of fuel V̇ NG (in particular at the inlet and / or front part of the anode path) and in particular (for this purpose) are controlled by a control unit, for example by the control unit adjusting a valve of the fuel mass flow controller. The volume flow of fuel V̇ NGhave a mass and / or a volume, in particular per unit of time. In other words, the amount of fuel per unit of time can be adjusted. The fuel mass flow controller can be arranged between the fuel valve and the anode path connection point or the recirculation unit.

[0174] The anode path connection point can be arranged between the fuel mass flow controller and the recirculation fan. This can be advantageous to enable influence by the recirculation fan and / or the first anode heat exchanger, particularly after mixing and / or before reaching the anode inlet. Thus, the flow velocity and / or the volume flow can be varied or adjusted by the recirculation fan. Heat can also be removed and / or added by the first and / or second anode heat exchanger. Preferably, the recirculation unit can be connected to the anode path connection point and advantageously supply the anode output stream at least partially to the anode input stream at the anode path connection point.

[0175] The recirculation unit can be included in the anode path, in particular form part of the anode path. The recirculation unit can be configured to supply the anode output stream (at least partially) to the anode input stream. As a result, the heat exchanger can receive the anode output stream completely or at least partially, in particular a recirculated volume flow, and then supply it to the anode input stream, in particular at an anode path connection point. The remaining portion of the anode output stream can be supplied to the burner. The first anode heat exchanger can receive water vapor and / or hydrogen contained in the anode output stream and then supply it to the anode input stream A in, in particular at an anode path connection point. This can create a circuit wherein (at least partially) the anode output stream, in particular a returned volume flow, is fed back into the anode input stream (in particular feedback). A recirculation rate r, i.e. in particular a proportion of the anode output stream that is returned, can be set by controlling the burner and / or the recirculation fan. The recirculation unit can be connected to the anode output and / or the anode path connection point, in particular arranged between them. The recirculation unit can have a line section which extends between the anode output or a branch to the burner, and an anode path connection point. Furthermore, the recirculation unit can be connected to the burner.The recirculation unit may comprise and / or be connected to the first anode path heat exchanger. In other words, the recirculation unit may feed the anode output stream (at least partially), in particular a recirculated volume flow, to the anode input stream by branching off a first portion through the burner, and a second portion (in particular the recirculated volume flow V̇). loop ), which is configured in particular as a function of the recirculation rate, is fed to the first anode path heat exchanger, in particular to a second inlet of the first anode path heat exchanger. The first anode path heat exchanger can be connected to the anode path connection point, in particular via a second outlet, and advantageously feed the (at least partially) branched anode output stream, in particular the second portion or the recirculated volume flow, to the anode input stream.

[0176] The recirculation fan can be connected to the fuel mass flow controller or the anode path connection point and / or the first anode heat exchanger, in particular arranged between them. The recirculation fan can adjust the recirculating volume flow and / or the flow velocity of the anode input stream (at this point). A recirculation sensor can be arranged before, on, in, and / or after the recirculation fan, which can be configured in particular to measure a recirculating volume flow. In particular, the measured value can be transmitted to the control unit to be taken into account preferably during control and / or regulation, in particular during calculation.It can be provided that by adjusting the recirculating volume flow, in particular for a given fuel volume flow, the recirculation rate is adjusted, in particular (in cooperation with the burner) the proportion of the anode output flow that is fed to the anode input flow (via the recirculation unit) is adjusted. The recirculating volume flow can be dependent on the fuel volume flow, and in particular on a (recirculated) volume flow (for example, these can be summed) that can be recirculated via the recirculation unit (at the anode path connection point).

[0177] The first anode heat exchanger can be connected to the recirculation fan and the second anode heat exchanger, in particular arranged between them. The first anode heat exchanger can have a first inlet connected to a first outlet, in particular for conducting the anode input flow. Furthermore, the first heat exchanger can have a second inlet and a second outlet, which can be configured to (at least partially) (re)circulate the anode output flow, in particular a recirculated volume flow. Heat can be transferred from the (branched or recirculated) anode output flow to the anode input flow. This can improve the efficiency and / or effectiveness, in particular by increasing the temperature of the anode input flow and / or the recirculating volume flow.

[0178] The second anode heat exchanger can be connected to the first anode heat exchanger and the reformer, in particular arranged between them. The second anode heat exchanger can have a first inlet which is connected to a first outlet, in particular for conducting the anode input stream. Furthermore, the second heat exchanger can have a second inlet and a second outlet, which can be configured to conduct (at least partially) the anode output stream, in particular the portion of the anode output stream that is not recirculated via the first anode heat exchanger. Preferably, the second anode heat exchanger can conduct a volume flow discharged from the burner. Heat can be transferred to the anode input stream. This can (further) improve the efficiency and / or effectiveness, in particular by increasing the temperature of the anode input stream and / or recirculating volume flow.

[0179] The reformer can be connected to the second anode heat exchanger and the anode inlet, in particular arranged between them. The reformer can be configured to convert alkanes into hydrocarbons and hydrogen (at least partially). This can increase the proportion of hydrogen usable in the fuel cell unit. The recirculation fan or reformer can be connected to the anode inlet.

[0180] The first lambda sensor can be connected to the second anode heat exchanger and the reformer, in particular arranged between them. The first lambda sensor can preferably be arranged upstream of, in particular shortly upstream of, the anode inlet, in particular the reformer, and / or connected to the anode inlet stream. The first lambda sensor can be configured to determine a first measurement signal. For this purpose, the first lambda sensor can be controlled by the control unit, in particular via a data connection, in order to then preferably measure the first measurement signal. Furthermore, the first lambda sensor can transmit the first measurement signal to the control unit, in particular via a or the data connection. The first measurement signal can preferably be specific for an oxygen-carbon ratio. The control unit can preferably calculate the oxygen-carbon ratio as a function of the first measurement signal.It can be provided that the first lambda sensor is configured to detect and / or measure oxygen, in particular an oxygen content. Alternatively or additionally, it can be provided that an oxygen sensor is arranged in the anode path, in particular near the anode inlet, and / or the control unit assumes, in particular by way of assumption, that a (soft) oxygen sensor is arranged there. This allows the oxygen-carbon ratio to be measured and / or calculated.

[0181] The second lambda sensor can be connected to the anode outlet and the burner or the second anode heat exchanger, in particular arranged between them. The second lambda sensor can preferably be arranged downstream of, in particular shortly after, the anode outlet, in particular upstream of the burner and / or the second anode heat exchanger, and / or connected to the anode output current. The second lambda sensor can be configured to determine a second measurement signal. For this purpose, the second lambda sensor can be controlled by the control unit, in particular via a data connection, in order to then preferably measure the second measurement signal. Furthermore, the second lambda sensor can transmit the second measurement signal to the control unit, in particular via a or the data connection. The second measurement signal can preferably be specific for a proportion of hydrogen at the anode outlet.Preferably, the control unit can calculate the proportion of hydrogen at the anode output as a function of the second measurement signal.

[0182] The cathode path can guide a material flow, in particular toward a cathode inlet (see below). The cathode path can also, at least partially, comprise a material flow from the cathode outlet. The cathode path can comprise, in particular guide, the cathode inlet current and / or the cathode outlet current.

[0183] The cathode input stream can (essentially) comprise the material flow from an air supply unit (in particular inlet for air into the system) to a cathode inlet.

[0184] The cathode inlet can be configured to receive a cathode input current and, in particular, to lead into the interior of the fuel cell unit.

[0185] The cathode output may be configured to output a cathode output current, and in particular may lead from the interior of the fuel cell unit.

[0186] An air supply unit can be configured to introduce the cathode input stream into the cathode path. The air supply unit can comprise an oxygen tank, an air tank, a filter, in particular an oxygen filter or air filter, and / or an intake device, for example, for intake of air. Accordingly, the cathode input stream, which is preferably introduced into the cathode path, can comprise oxygen and / or air.

[0187] In this case, an air blower, in particular for controlling and / or regulating a flow rate, a volume flow and / or a mass flow of the cathode input flow, can be provided, which is preferably arranged between the air supply unit and the cathode path heat exchanger, and in particular is connected to them.

[0188] A cathode path heat exchanger can be connected to the air blower and the cathode inlet, and in particular can be arranged between them. The cathode path heat exchanger can have a first inlet which is connected to a first outlet, in particular for conducting the cathode inlet stream. The cathode path heat exchanger can have a second inlet which is connected to a second outlet, in particular for conducting the cathode outlet stream and / or the volume flow which is discharged from the burner. In this case, the cathode path heat exchanger can preferably (only) exchange orprovide a transfer of heat, in particular from the cathode output stream to the cathode input stream, the temperature of which preferably increases in order to advantageously already have a higher temperature at the cathode inlet, wherein advantageously the temperature of the cathode output stream is reduced before it is fed to the cathode path heat exchanger.

[0189] The burner can preferably be arranged between the cathode outlet and the cathode path heat exchanger and / or the second anode heat exchanger, and in particular can be connected to them. It can be provided that the anode output stream is at least partially fed to the burner, in particular the anode output stream less a recirculated volume flow. The cathode output stream and / or anode output stream can be combusted, in particular partially, by the burner. The burner can preferably be configured to (at least partially) combust (excess or unreacted) fuel. This can cause wear and / or damage to the burner. Accordingly, the fuel utilization of the fuel cell unit can advantageously be optimized by (optimized) control and / or regulation, whereby the burner advantageously has to burn less (excess) fuel.This allows the recirculation rate to be influenced and / or adjusted. In particular, air, oxygen, ammonia, and / or (flammable) chemical compounds, particularly including hydrogen, can be burned. Preferably, the burner can be controlled and / or regulated by the control unit. In particular, this allows adjustment of the temperature, the proportion of the anode output current, and / or the supply of additional substances.

[0190] The air outlet can guide the cathode output stream, in particular air, out of the cathode path or allow it to escape. The air outlet can be connected to the cathode path heat exchanger, in particular to its (second) outlet. If a burner is provided, its combustion products can be expelled via the air outlet. The anode output stream can also be expelled, at least partially, via the air outlet after being fed to the burner, in particular after combustion.

[0191] The fuel cell unit can comprise an electrolyte, in particular in the form of a solid (preferably) and / or a membrane, along the sides of which the cathode path and the anode path, or the corresponding material flows, are guided, preferably to enable an (exothermic) redox reaction. This can generate thermal and / or electrical energy.

[0192] Unless otherwise stated, transport between different components of the fuel cell unit can be achieved through connecting units, such as pipes. This can enable material flow to operate the fuel cell system.

[0193] The first anode heat exchanger, the second anode heat exchanger, and / or the cathode path heat exchanger can each have a first inlet connected to a first outlet and a second inlet connected to a second outlet. Preferably, no material or material flow can occur between the first inlet / outlet and the second inlet / outlet. Preferably, only (thermal) energy can be exchanged. Thus, it can be provided that a respective volume flow (or molar flow) does not change when passing through a first anode heat exchanger, second anode heat exchanger, and / or cathode path heat exchanger.

[0194] A high-temperature region can be provided, which in particular includes the fuel cell unit, the cathode path heat exchanger, the second anode heat exchanger, the burner, the cathode inlet, the cathode outlet, the reformer, the first lambda sensor, the second lambda sensor, the anode inlet, and / or the anode outlet. The temperature in the high-temperature region can be (relatively) high; for this purpose, it can be thermally insulated, in particular. In particular, the temperature of the fuel cell unit can be present in the fuel cell unit, which in particular represents the maximum temperature in the fuel cell system.

[0195] The fuel cell system can achieve fuel utilization FU Sysof the fuel cell system, which is particularly specific to the degree to which the fuel cell system (efficiently) uses (available) fuel. This can (therefore) relate to the fuel cell system (overall system), in particular characterizing it.

[0196] The fuel cell system, in particular the fuel cell unit, can achieve fuel utilization FU Stk of the fuel cell unit, which is particularly specific to the degree to which the fuel cell unit (efficiently) uses (available) fuel. This can (therefore) relate to the fuel cell unit (subsystem), in particular characterizing it.

[0197] This results in the same advantages with respect to a fuel cell system according to the invention according to the second aspect as have already been described with respect to a method according to the invention according to the first aspect.

[0198] Furthermore, it is conceivable that the fuel cell system has a first lambda sensor for measuring a first measurement signal and / or a second lambda sensor for measuring a second measurement signal in the anode path, wherein the control unit is configured to calculate at least one controlled variable as a function of the first measurement signal and / or second measurement signal, wherein in particular - the first lambda sensor is configured to detect a first measurement signal, wherein the control unit is configured to determine an oxygen-carbon ratio (OC An,in ) at the anode input, and / or - the second lambda sensor is designed to detect a second measurement signal, wherein the control unit is designed to determine a proportion of hydrogen (x H2,An,out ) at the anode output.

[0199] The first and / or second lambda sensor can be configured as a soft sensor. The measurement signals can be provided and / or calculated, in particular by the control unit. During operation, in particular during calculation and / or control by the control unit, it can be assumed that the first and / or second measurement signals were provided, in particular by a first and / or second (physical and / or software-based) sensor.

[0200] The above object is achieved 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 the computer to implement the method according to the first aspect.

[0201] 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 invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect.

[0202] The above object is further achieved 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 the computer to carry out the method according to the first aspect.

[0203] 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 invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect and / or a computer program product according to the invention according to the third aspect.

[0204] The above object is further achieved according to a fifth aspect by a control unit according to the invention, comprising a computing unit and a memory unit in which instructions are stored which, when at least partially executed by the computing unit, carry out a method according to the first aspect, wherein in particular the control unit has a control loop, in particular comprising a feed-forward control and / or a closed-loop control.

[0205] It can be provided that the control unit, in particular the computing unit, carries out and / or initiates the method steps, for example by controlling the fuel cell system and / or its (above-mentioned) components. The control unit can send control signals to corresponding actuators of the fuel cell system in order to adjust them. The control unit can also receive sensor signals from sensors of the fuel cell system, for example, the first and / or second lambda sensor, which are taken into account in particular during control and / or regulation. Based on these signals, for example, target values ​​can be calculated.The control unit, in particular the control loop, for example the feed-forward control, closed-loop control, I-part, and / or P-part, can be connected to the fuel tank, the fuel valve, the fuel mass flow controller, the recirculation blower, the recirculation unit, the first lambda sensor, the second lambda sensor, the temperature sensor, the air supply unit, the air blower, the burner, the air outlet, the inverter and / or the fuel cell unit, preferably via a data connection, for controlling and / or regulating purposes, wherein an exchange of a first measurement signal, a second measurement signal, a controlled variable, a disturbance variable and / or a manipulated variable can advantageously be carried out via the corresponding data connection.The aforementioned components can each have an actuator that can be controlled by the control unit, for example, for adjusting a valve, controlling a sensor, and / or transmitting data (e.g., acquired sensor data). Furthermore, the aforementioned components can each have a sensor configured to detect temperature, pressure, volume flow, and / or other relevant parameters. The acquired results can be sent to the control unit, in particular via a data connection, to be considered, preferably, in a control and / or regulation process, in particular a calculation process.

[0206] A feed-forward control may be provided to enable start-up and / or basic operation of the fuel cell system. The feed-forward control may specify initial values.

[0207] It can be provided that the closed-loop control, particularly after starting and / or running up the fuel cell system, performs control and / or regulation of the fuel cell system in addition to and / or as an alternative to the feedforward control. This allows for (particularly fine) optimization of the operation of the fuel cell system.

[0208] 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 invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect and / or a computer program product according to the invention according to the third aspect and / or a computer-readable data carrier according to the invention according to the fourth aspect.

[0209] The above object is further achieved 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.

[0210] A system may comprise a (residential) building, an industrial building, a power plant, a storage facility, a vehicle, a ship, an aircraft, or another system with, in particular, increased energy requirements. It may be particularly preferred to provide a (substantially) stationary (immobile) application of the fuel cell system.

[0211] 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 invention according to the first aspect and / or a fuel cell system according to the invention according to the second aspect and / or a computer program product according to the invention according to the third aspect and / or a computer-readable data carrier according to the invention according to the fourth aspect and / or a control unit according to the invention according to the fifth aspect.

[0212] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. These schematically show: Fig. 1 a procedure, Fig. 2 a system, Fig. 3 a fuel cell system, Fig. 4 a control unit or a control circuit, Fig. 5 a Range R, Fig. 6 a control loop, Fig. 7 a look-up table, Fig. 8 a control loop, Fig. 9 a control loop, Fig. 10 a control unit or a control circuit, Fig. 11 a control loop, Fig. 12 a control loop or activation, and Fig. 13 a control loop with adaptation unit.

[0213] In the following figures, identical reference numerals are used for the same technical features, even for different embodiments.

[0214] Fig. 1 shows a method for operating, in particular for controlling and / or regulating a fuel cell system 100, in particular a solid oxide fuel cell system, comprising - having an anode path 10 ◯ an anode input 18 for receiving an anode input current A in and ◯ an anode output 19 for outputting an anode output current A out , and ◯ a recirculation unit 19.1 for at least partially recirculating the anode output current A out into the anode input current A in , in particular a recirculating volume flow V̇ loop , the method comprising - receiving 110, by a control unit FCCU, at least one controlled variable CV, wherein the at least one controlled variable CV is specific to the anode path 10, - Calculating 120, by the control unit FCCU, at least one manipulated variable MV as a function of the at least one controlled variable CV, - Controlling 130, by the control unit FCCU, the fuel cell system 100 as a function of the at least one manipulated variable MV, whereupon the fuel cell system 100 is adjusted in order in particular to prevent fuel depletion of the fuel cell system 100.

[0215] It can be provided that the receiving 110, by the control unit FCCU, comprises - Measuring 111, by a first lambda sensor λ1, a first measurement signal M1, which is representative of an oxygen-carbon ratio OC An,in at the anode input 18 is specific, - Measuring 112, by a second lambda sensor λ2 of a second measurement signal M2, which represents a proportion of hydrogen x H2,An,out at the anode output 19 is specific, - Calculate 113 of the oxygen-carbon ratio OC An,in at the anode input 18 depending on the first measuring signal M1, - Calculate 114 of the proportion of hydrogen xH2,An,out at the anode output 19 depending on the second measuring signal M2.

[0216] In addition, it is conceivable that the receiving 110, calculating 120 and / or controlling 130 by the control unit FCCU, by a control loop of the control unit FCCU, comprises calculating 121 a range R of at least one manipulated variable MV, which is designed to enable improved operation of the fuel cell system 100, wherein in particular the range R comprises a minimum volume flow of fuel V̇ NG,Min and a maximum volume flow of fuel V̇ NG,Max has.

[0217] Fig. 2 shows, by way of example, a system 200 comprising a fuel cell system 100 and a control unit FCCU. The control unit FCCU can have a computing unit CU and a memory unit MU. The fuel cell system 100 and the control unit FCCU can be connected for data communication via a data connection.

[0218] Fig. 3 shows an example of an anode path 10, as may be provided in particular in a fuel cell system 100. The anode path 10 may be configured to supply a fuel, e.g., natural gas, to the anode inlet 18 of a fuel cell unit 101. The fuel may be fed in via a fuel tank 11, in particular alternatively or additionally via a fuel network. The fuel tank 11 may be connected to a desulfurization unit 11.1. The desulfurization unit 11.1 may be connected to a fuel valve 12, which may prevent or permit the inflow, in particular depending on an actuator, which may be adjustable, for example, via a control unit FCCU. A fuel mass flow controller 13 may control the volume flow of fuel V̇ NG Furthermore, a recirculation fan 14 can be used to create a recirculating volume flow V̇ recyat this point of the anode path 10. For this purpose, the recirculation fan 14 can be controlled by a control unit FCCU. The volume flow can then be passed through a first anode heat exchanger 15, which in particular enables heating. The anode path 10 can then be connected to the anode inlet 18, for example via a second anode heat exchanger 16 and / or a reformer 17. At the anode inlet 18, the anode inlet current A in into the fuel cell unit 101. The anode input current A in a (molar) fraction x i,NG of fuel. Within the fuel cell unit 101, the volume flow is guided from the anode inlet 18 to an anode outlet 19. From the anode outlet 19, the anode output current A out , at least partially, e.g. as returned volume flow V̇ loop, are led to the first anode heat exchanger 15, wherein the returned volume flow V̇ loop , for example via a recirculation unit 19.1 through the first anode heat exchanger 15, to an anode path connection point 13.1. The returned volume flow V̇ loop can be adjusted depending on a recirculation rate r. The part of the anode output flow that is not returned as volume flow V̇ loop via the recirculation unit 19.1 can be fed into a burner 26. The anode input current A can therefore be fed via the recirculation unit 19.1 in at least partially (especially in the form of the returned volume flow V̇ loop ) the anode input current A in, in particular at the anode path connection point 13.1. A first lambda sensor λ1 and / or a second lambda sensor λ2 can be arranged in the anode path 10 or connected thereto in order to measure a first measurement signal M1 and / or a second measurement signal M2, which are preferably transmitted to the control unit FCCU. Depending on the first measurement signal M1, the control unit FCCU can determine an (actual) oxygen-carbon ratio (OC An,in ) at the anode input 18. Depending on the second measurement signal M2, the control unit FCCU can determine an (actual) proportion of hydrogen x H2,an,out at the anode output 19. Preferably, at least one controlled variable CV, in particular x H2,An,out and / or by the control unit FCCU by controlling 130.

[0219] The cathode path 20 may have an air supply unit 21 (as a “starting point”), via which air can be introduced into the cathode path 20, e.g. as cathode input current K in . It can be provided that the air supply unit 21 introduces ambient air into the cathode path. Subsequently, the corresponding volume flow can be guided via an air blower 22, which can in particular accelerate the volume flow. Furthermore, the cathode input current K in then passed through a cathode path heat exchanger 23 before being fed into the fuel cell unit 101 via a cathode inlet 24. Inside the fuel cell unit 101, the cathode input current K in or volume flow from the cathode inlet 24 to a cathode outlet 25, and in particular as cathode output current K out The cathode output current K outcan then be fed into the burner 26. The (outlet of the) burner 26 is connected to the first anode heat exchanger 16, wherein in particular the cathode output stream K out to the cathode path heat exchanger 23 before it leaves the fuel cell system 100, preferably via an air outlet 27 from the cathode path 20.

[0220] A corresponding reaction can take place inside the fuel cell unit 101 in order to advantageously produce energy, in particular a current I or i Stk and / or to generate a voltage. For this purpose, the fuel cell system 100, in particular the fuel cell unit 101, can have an inverter 40. In a high-temperature region 102, the temperature can be (relatively) high; for this purpose, this region can in particular be thermally insulated. The fuel cell unit can, for example, have a (disturbance variable DV) temperature t StkThe fuel cell unit 101 can have a fuel utilization FU Stk This can in particular comprise a quantification of the proportion of fuel used, in particular with respect to the fuel cell unit 101. The fuel cell system 100 can have a fuel utilization FU sys This can in particular include a quantification of the proportion of the (efficiently) used fuel, in particular with respect to the fuel cell system 100. The fuel cell system 100 can have a minimum / maximum fuel utilization FU Sys,Min / Max , whereby these can in particular specify a range of (at all) adjustable values.

[0221] The control unit FCCU may have at least one, preferably all, of the following features: - Feed-Forward Control ffc - Closed-Loop Control clc - I-Control I - Part, and / or - P-controller P - Part

[0222] The FCCU control unit can calculate a range R within which values ​​can be located or should be set by control. The FCCU control unit can thereby calculate disturbance variables DV, in particular a (molar) proportion of fuel x I,NG in the anode input current and / or a current I, e.g., via a data connection. For control, the control unit FCCU can receive at least one manipulated value MV, in particular V̇ NG and / or V̇ recy , by controlling and / or adjusting the fuel mass flow controller 13 and / or the recirculation fan 14, e.g. via a data connection. In the control unit, a controlled variable x H2,An,out,sp for the proportion of hydrogen at the anode outlet and / or a controlled variable OC An,in,sp for oxygen-carbon ratio at the anode inlet, which may be specific for an operating point, for example.

[0223] Fig. 4 (see also above) shows the control unit FCCU, or a (first) control loop for x H2,An,out,sp .

[0224] Fig. 5 (see also above) shows an example of a range R.

[0225] Fig. 6 (see also above) shows a (first) control loop.

[0226] Fig. 7 (see also above) shows a look-up table.

[0227] Fig. 8 (see also above) shows a (first) control loop.

[0228] Fig. 9 (see also above) shows a (first) control loop.

[0229] Fig. 10 (see also above) shows the control unit FCCU, or a (first) control circuit for OC an,in,sp .

[0230] Fig. 11 (see also above) shows a (second) control loop.

[0231] Fig. 12 (see also above) shows a control loop or activation.

[0232] Fig.13 (see also above) shows a control loop with adaptation unit for adaptation. List of reference symbols 10 Anode path 11 Fuel tank 11 11.1 Desulfurization unit 11.1 12 Fuel valve 12 13 Fuel mass flow controller 13 V NG Volume flow of fuel V̇ NG 13.1 Anode path connection point 13.1 14 Recirculation fan 14 V recy recirculating volume flow V̇ recy 15 first anode heat exchanger 15 16 second anode heat exchanger 16 λ1 first lambda sensor 17 Reformers 17 18 Anode input 18 A in Anode input current A in 19 Anode output 19 A out Anode output current A out λ2 second lambda sensor 19.1 Recirculation unit 19.1 V looprecirculated volume flow r recirculation rate 20 Cathode path 21 Air supply unit 21 22 Air blower 22 23 Cathode path heat exchanger 23 24 Cathode input 24 K in Cathode input current K in 25 Cathode output 25 K out Cathode output current K out 26 burners 26 27 Air outlet 27 40 Inverters 40 100 fuel cell system FU Sys Fuel utilization FU Sys of the fuel cell system 100 FU Sys,Min minimal fuel utilization FU Sys of the fuel cell system 100 FU Sys,M\ax maximum fuel utilization FU Sys of the fuel cell system 100 FU Sys,Min / Max minimum / maximum fuel utilization FU Sys of the fuel cell system 100 101 Fuel cell unit 101 FU Stk Fuel utilization FU Stk the fuel cell unit 101 102 high temperature range 110 Receiving at least one controlled variable CV 111 Control of a first lambda sensor 112 Controlling a second lambda sensor 113 Calculating the oxygen-carbon ratio OC An,in at the anode input 18 114 Calculating the proportion of hydrogen x H2,An,out at the anode output 19 120 Calculate at least one manipulated variable MV 121 Calculating a range R of at least one manipulated variable MV 130 Control depending on the manipulated variable MV 200 systems FCCU control unit CU computing unit MU storage unit ffc Feed-Forward Control clc Closed-Loop Control I-Part I-Controller P-Part P-Controller CV controlled value, especially OC An,in, x H2,An,out DV disturbance value, in particular I, i Stk , x i,NG , t Stk MV manipulated value, especially V̇ NG , V̇ recy R Range of at least one manipulated variable MV M1 first measurement signal M2 second measurement signal x H2,An,out (Actual) proportion of hydrogen (x H2,An,out ) at the anode output x H2,An,out,sp Target value for the proportion of hydrogen at the anode outlet V NG,ffc first control component for the volume flow of fuel V NG,P-Par t second control component for the volume flow of fuel V NG,I-Part third control component for the volume flow of fuel V NG,Min / Max minimum / maximum volume flow of fuel Rate of change of volume flow of fuel minimum / maximum rate of change of the volume flow of fuel VNG,Min / Max,#1 first minimum / maximum volume flow of fuel first minimum / maximum rate of change of the volume flow of fuel V NG,Min / Max,#2 second minimum / maximum volume flow of fuel second minimum / maximum rate of change of the volume flow of fuel OC An,in (Actual) oxygen-carbon ratio at the anode inlet OC An,in,sp Target value for oxygen-carbon ratio at the anode inlet V recy,ffc first control component for the recirculating volume flow V recy,I-Part second control component for the recirculating volume flow V recy,P-Part third control component for the recirculating volume flow V recy,Min / Max minimum / maximum recirculating volume flow V recy Rate of change of the recirculating volume flow minimum / maximum rate of change of the recirculating volume flow V recy,Min / Max,#1 first minimum / maximum recirculating volume flow first minimum / maximum rate of change of the recirculating volume flow V recy,Min / Max,#2 second minimum / maximum recirculating volume flow second minimum / maximum rate of change of the recirculating volume flow ratelim rate limiter vallim value limiter x i,NG (Molar) fraction of fuel in the anode input stream t Stk Fuel cell unit temperature 101 i Stk Fuel cell unit current 101 i Stk,Max maximum current of the fuel cell unit 101 I Current b act,Cont Activation signal for the control loop b act,Adapt Activation signal for adaptation unit Adapt adaptation unit

Claims

[1] Method for operating, in particular for controlling and / or regulating a fuel cell system (100), in particular a solid oxide fuel cell system, comprising - having an anode path (10) o an anode input (18) for receiving an anode input current (A in ) and o an anode output (19) for outputting an anode output current (A out ), and o a recirculation unit (19.1) for at least partially recirculating the anode output current (A out ) into the anode input current (A in ), in particular a recirculating volume flow (V̇ loop ), comprising the method - receiving (110), by a control unit (FCCU), at least one controlled variable (CV), wherein the at least one controlled variable (CV) is specific for the anode path (10), - calculating (120), by the control unit (FCCU), at least one manipulated variable (MV) as a function of the at least one controlled variable (CV), - controlling (130), by the control unit (FCCU), the fuel cell system (100) as a function of the at least one manipulated variable (MV), whereupon the fuel cell system (100) is adjusted in order in particular to prevent fuel depletion of the fuel cell system (100). [2] Method according to claim 1, characterized by that the at least one controlled variable (CV) is an oxygen-carbon ratio (OC An,in ) at the anode inlet (18) and / or a proportion of hydrogen (x H2,An,out ) at the anode output (19). [3] Method according to one of the preceding claims, characterized by that the at least one control variable (MV) is a volume flow of fuel (V̇ NG ) and / or a recirculating volume flow (V̇ recy), wherein in particular the recirculating volume flow (V̇ recy ) is designed to adjust the at least partial return of the anode output current (A out ) into the anode input current (A in ), in particular a recirculating volume flow (V̇ loop ), via the recirculation unit (19.1), wherein preferably the recirculating volume flow (V̇ recy ) depending on the volume flow of fuel (V̇ NG ) is calculated. [4] Method according to one of the preceding claims, characterized by that the receiving (110), by a control unit (FCCU), comprises receiving at least one disturbance variable (DV), in particular comprising a current (I), a temperature (t Stk ) of the fuel cell unit (101) and / or a proportion of fuel (x i,NG ) in the anode input current (A in), wherein the calculation (120) of at least one manipulated variable (MV) is carried out by the control unit (FCCU) as a function of the at least one disturbance variable (DV). [5] Method according to one of the preceding claims, characterized by that the receiving (110), by the control unit (FCCU), comprises - measuring (111), by a first lambda sensor (λ1), a first measurement signal (M1) which is representative of an oxygen-carbon ratio (OC An,in ) at the anode input (18) is specific, - measuring (112), by a second lambda sensor (λ2) a second measurement signal (M2) which is representative of a proportion of hydrogen (x H2,An,out ) at the anode output (19) is specific, - Calculate (113) the oxygen-carbon ratio (OC An,in ) at the anode input (18) depending on the first measuring signal (M1), - Calculate (114) the proportion of hydrogen (x H2,An,out)at the anode output (19) depending on the second measuring signal (M2). [6] Method according to one of the preceding claims, characterized by that the receiving (110), calculating (120) and / or controlling (130) by the control unit (FCCU) is carried out by a control circuit of the control unit (FCCU), comprising - a feed-forward control (ffc) for pre-control, which is set up o a first control component (V̇ NG,ffc ) for the volume flow of fuel (V̇ NG ), - a closed-loop control (clc), which is set up o a second control component (V̇ NG,P-Part ) for the volume flow of fuel (V̇ NG ) and a third control component (V̇ NG,I-Part ) for the volume flow of fuel (V̇ NG ), - wherein the control unit (FCCU) is configured to control the at least one manipulated variable (MV), in particular a volume flow of fuel (V̇ NG ), depending on the first control component (V̇ NG,ffc ), second control component (V̇ NG,P-part ) and third control component (V̇ NG,I-Part ) for the volume flow of fuel (V̇ NG ). [7] Method according to one of the preceding claims, characterized by that the receiving (110), calculating (120) and / or controlling (130) by the control unit (FCCU) is carried out by a control circuit of the control unit (FCCU), comprising - a feed-forward control (ffc) for pre-control, which is set up o a first control component (V̇ recy,ffc ) for the recirculating volume flow (V̇ recy ), - a closed-loop control (clc), which is set up o a second control component (V̇ recy,P-Part) for the recirculating volume flow (V̇ recy ) and a third control component (V̇ recy,I-Part ) for the recirculating volume flow (V̇ recy ), - wherein the control unit (FCCU) is configured to control the at least one manipulated variable (MV), in particular a recirculating volume flow (V̇ recy ), depending on the first control component (V̇ recy,ffc ), second control component (V̇ recy,P-Part ) and third control component (V̇ recy,I-Part ) for the recirculating volume flow (V̇ recy ). [8] Method according to one of the preceding claims 6 or 7, characterized by that the closed-loop control (clc) has - a P-controller (P-part) which is designed to o a second control component (V̇ NG,P-Part ) for the volume flow of fuel (V̇ NG ) and o a second control component (V̇ recy,P-Part ) for the recirculating volume flow (V̇recy ), - an I-controller (I-Part) which is set up to ◯ a third control component (V̇ NG,I-part ) for the volume flow of fuel (V̇ NG ) and ◯ a third control component (V̇ recy,I-Part ) for the recirculating volume flow (V̇ recy ). [9] Method according to one of the preceding claims, characterized by that the receiving (110), calculating (120) and / or controlling (130) by the control unit (FCCU), by a control circuit of the control unit (FCCU), comprises calculating (121) a range (R) of at least one manipulated variable (MV), which is designed to enable improved operation of the fuel cell system (100), wherein in particular the range (R) has a minimum volume flow of fuel (V̇ NG,Min ) and a maximum volume flow of fuel (V̇ NG,Max ). [10] Fuel cell system (100), in particular solid oxide fuel cell system, comprising - having an anode path (10) o an anode input (18) for receiving an anode input current (A in ) and o an anode output (19) for outputting an anode output current (A out ), and o a recirculation unit (19.1) for at least partially recirculating the anode output current (A out ) into the anode input current (A in ), - wherein the fuel cell system (100) is configured to be controlled by a control unit (FCCU) in order to implement the method according to one of the preceding claims, in particular in order to prevent fuel depletion of the fuel cell system (100). [11] Fuel cell system (100) according to the preceding claim, characterized bythat the fuel cell system (100) has a first lambda sensor for measuring a first measurement signal (M1) and / or a second lambda sensor for measuring a second measurement signal (M2) in the anode path (10), wherein the control unit (FCCU) is configured to calculate at least one controlled variable (CV) as a function of the first measurement signal (M1) and / or second measurement signal (M2), wherein in particular - the first lambda sensor is configured to detect a first measurement signal (M1), wherein the control unit (FCCU) is configured to determine an oxygen-carbon ratio (OC An,in ) at the anode input (18), and / or - the second lambda sensor is designed to detect a second measurement signal (M2), wherein the control unit (FCCU) is designed to determine a proportion of hydrogen (x H2,An,out )at the anode output (19). [12] A computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to implement the method according to any one of the preceding claims 1 to 9. [13] Computer-readable data carrier in which instructions are stored which, when executed by a computer, cause the computer to carry out the method according to one of the preceding claims 1 to 9. [14] Control unit (FCCU), comprising a computing unit (CU) and a memory unit (MU) in which instructions are stored which, when at least partially executed by the computing unit (CU), carry out a method according to one of the preceding claims 1 to 9, wherein in particular the control unit (FCCU) has a control loop, in particular comprising a feed-forward control (ffc) and / or a closed-loop control (clc). [15] System (200) comprising a fuel cell system (100) according to claim 10 or 11 and / or a control unit (FCCU) according to claim 14.

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