Method for determining a mass flow rate

Abstract

The invention relates to a method for determining a mass flow rate (m_dot_H2) of fuel, in particular hydrogen, for a fuel cell (100), in particular a proton exchange membrane fuel cell, comprising: - determining (110), by means of a control unit (FCCU), a valve mass flow rate (m_dot_H2PrpVlv) which is specific to a fuel valve (10) of the fuel cell (100), - determining (120), by means of the control unit (FCCU), a mass flow rate rough estimation (m_dot_H2_rough) depending on the valve mass flow rate (m_dot_H2PrpVlv), - calculating (130), by means of the control unit (FCCU), a mass flow rate refinement (delta_m_dot_H2_Refine) depending on the mass flow rate rough estimation (m_dot_H2_rough), - ascertaining (140), by means of the control unit (FCCU), a mass flow rate of fuel (m_dot_H2) depending on the mass flow rate rough estimation (m_dot_H2_rough) and the mass flow rate refinement (delta_m_dot_H2_Refine).

Description

[0001] Description

[0002] title

[0003] Method for determining a mass flow

[0004] The invention relates to a method having the features of the independent method 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 fuel cell system having the features of the independent device claim.

[0005] Fuel cell systems are known, in particular proton exchange membrane fuel cells, comprising at least one fuel cell unit having an anode and a cathode and an intermediate electrolyte, e.g. a proton exchange membrane (PEM). A fuel, for example hydrogen, 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, e.g. hydrogen. There can be an excess of oxygen on the cathode side, while there can be a deficiency of oxygen on the anode side. Hydrogen ions can diffuse through the electrolyte from the anode to the cathode, where they produce water.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 have a stack of the fuel cell units described above. The state of the art has disadvantages. For example, the mass flow of fuel may not be known or may not be known precisely. Furthermore, the mass flow of fuel may not be taken into account or may only be inadequately taken into account during operation, particularly during control and / or regulation of the fuel cell system. Assumptions and / or measurements may either be missing or in need of improvement. In addition, known methods and / or fuel cell systems may be too complicated and / or too cost-intensive. Furthermore, the control and / or regulation may be inadequate.

[0006] The above object is achieved by a method having the features of the independent method 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 fuel cell system having the features of the independent device claim. 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 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 fuel cell 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, and / or fifth aspect also apply to the first, second, third, fourth, and / or fifth aspect.

[0007] The above object is achieved according to a first aspect by a method for determining a mass flow of fuel, in particular hydrogen, for a fuel cell, in particular a proton exchange membrane fuel cell, comprising:

[0008] Determining, by a control unit, a valve mass flow which is specific for a fuel valve of the fuel cell, determining, by the control unit, a coarse mass flow estimate as a function of the valve mass flow, calculating, by the control unit, a mass flow refinement as a function of the coarse mass flow estimate, determining, by the control unit, a mass flow of fuel as a function of the coarse mass flow estimate and the mass flow refinement.

[0009] The method can be computer-implemented. The described actions or features of the method can be carried out in the order shown, and in particular can be carried out repeatedly. The method can preferably be used to control and / or regulate a fuel cell system according to the fifth aspect. In this case, a control unit according to the fourth aspect can particularly preferably be used for determining, calculating, ascertaining, and / or operating, controlling and / or regulating. The control unit can carry out the corresponding actions or features and / or carry out control in order to preferably implement the actions. The method can preferably be carried out as part of commissioning and / or an end-of-line test. The method can preferably be carried out for a (specific) fuel cell system.

[0010] The invention can be used for various fuels, preferably hydrogen. Accordingly, hydrogen can be used for illustrative purposes / explanation. However, other fuels, especially those containing hydrogen, are also conceivable.

[0011] The determination of a valve mass flow can be carried out as a function of a pressure of (inflowing) fuel, in particular at the fuel valve (for example from a fuel tank). The pressure can particularly preferably be measured by a pressure sensor on and / or in the fuel valve. It can be particularly preferred for a pressure sensor to be provided, in particular on the fuel valve, and / or to be comprised by the fuel valve. This can be configured to measure the pressure and to transmit it, in particular via a data connection, to the control unit. Alternatively or additionally, the determination can be carried out by a mass flow sensor, in particular during commissioning, calibration and / or an end-of-line test of the fuel cell, in particular on or near the fuel valve.In this case, it can be provided that the mass flow sensor transmits the measured mass flow, in particular via a data connection, to the control unit. It can preferably be provided that no mass flow sensor is provided during operation and / or regular operation of the fuel cell system. Preferably, a mass flow can be determined (only and / or exclusively) based on a control current.

[0012] Determining a rough mass flow estimate as a function of the valve mass flow can involve equating the two. Accordingly, the valve mass flow can be used (initially) (particularly as an assumption) for the rough mass flow estimate. The method allows for a better and more accurate determination. This can be advantageous, since fuel, in particular, can (undesirably) escape, e.g., on the way to the fuel cell unit, for example, due to high pressure and / or leaks. The rough mass flow estimate can include a (roughly estimated or approximated) mass flow as a function of a control current.

[0013] The calculation of a mass flow refinement can be carried out as a function of the rough mass flow estimate, in particular starting from the rough mass flow estimate. The rough mass flow estimate can be used as input. The mass flow refinement can comprise a (calculated or estimated) mass flow as a function of a control current. The mass flow refinement can preferably differ from the rough mass flow estimate. Preferably, the mass flow refinement is configured for readjustment and / or a more precise determination of the mass flow of fuel. The determination of a mass flow of fuel can preferably comprise or represent an end result. The mass flow of fuel, e.g., of hydrogen, can be configured as a function of a control current of the fuel valve.Accordingly, the mass flow of fuel, in particular during operation and / or regular operation of the fuel cell system, can be determined via the (set) control current of the fuel valve, in particular by the control unit. The control unit can preferably set the control current. The control current and / or a specific control signal can be provided to the fuel valve by the control unit, in particular via a data connection. Preferably, a setting and / or valve position and / or opening of the fuel valve can be or can be set as a function of the control current. During commissioning and / or an end-of-line test, different and / or a plurality of control currents can be set, wherein preferably the corresponding pressure (of the fuel) and / or the valve mass flow are measured and / or determined.Accordingly, different and / or a multitude of operating points and / or calibration curves can result. Accordingly, the mass flow of fuel can be determined (later during operation) as a function of the pressure and / or the control current. Preferably, a (more precise) determination of the mass flow of fuel can be enabled, in particular without providing a mass flow sensor designed for this purpose.

[0014] Within the scope of the invention, it is conceivable that the determination of the valve mass flow is carried out as a function of a control current of the fuel valve, wherein in particular the opening of the fuel valve is adjustable as a function of the control current.

[0015] The valve mass flow can exhibit a characteristic behavior depending on the control current (see figures). In other words, setting a (value for the) control current can result in a specific valve mass flow. The control current can preferably be set by the control unit. The control current and / or a specific control signal therefor can be provided by the control unit to the fuel valve, in particular via a data connection. Preferably, a setting and / or valve position and / or opening of the fuel valve can be or can be set depending on the control current. The control unit can have a current source and / or function as such in order to provide a control current.Alternatively or additionally, it can be provided that a control current unit provides the control current, which is preferably controlled and / or monitored by the control unit.

[0016] It can be provided within the scope of the invention that the determination of the valve mass flow comprises filtering, in particular low-pass filtering, of the control current.

[0017] This can be advantageous for using simpler and / or more cost-effective control units and / or control current units. For example, these can be configured to provide a control current by closing and / or opening a relay at a specific, particularly comparatively low, frequency. Filtering, particularly low-pass filtering, can thus filter out interference frequencies. It can be provided that, particularly if filtering has been performed, a filtered control current is meant when a control current is described within the scope of the invention.

[0018] It is further conceivable that determining the valve mass flow comprises removing a hysteresis part of the valve mass flow, wherein the valve mass flow has at least partially a hysteresis, comprising two hysteresis parts, as a function of the control current, and preferably during the removal a hysteresis part is deleted which is specific for an increasing control current or a hysteresis part is deleted which is specific for a decreasing control current.

[0019] The fuel valve can, at least in part, exhibit a path-dependent behavior and / or hysteresis depending on the control current (see also figures). A hysteresis can have two hysteresis components, e.g., a left and a right, or one when closing / reducing the control current and one when opening / increasing the control current. Preferably, only one hysteresis component is used for the method; in particular, it can preferably be provided that a (left) hysteresis component is retained that is specific to and / or describes a falling / decreasing control current. Advantageously, greater accuracy can therefore be achieved and / or a clear (functional) assignment of a mass flow as a function of the control current can be enabled.It may be advantageous to use the left hysteresis part, as this may have higher accuracy and / or a (comparatively) softer / smoother transition. Alternatively, it may be possible to cancel a hysteresis part specific to a decreasing control current (the left part).

[0020] It is also conceivable that determining the valve mass flow comprises limiting the valve mass flow to a valve mass flow interval, and in particular comprises limiting the control current to a control current interval and / or the pressure to a pressure interval.

[0021] In other words, the respective range can be cropped and / or shortened. This can reduce memory and / or computing power. This can improve accuracy, particularly during fitting, since a more precise and / or appropriate fit is possible, especially for a narrower and / or restricted interval (e.g., with a lower [mean] square deviation). Furthermore, this can save data and / or measurements (including in advance), which enables faster commissioning and / or end-of-line testing. It can be provided that the control current, mass flow, and / or pressure are smoothed and / or completed by interpolation between values ​​or operating points. This can enable a continuous and / or uninterrupted curve. This can lead to greater accuracy.The valve mass flow interval, control current interval and / or pressure interval can be selected such that realistic and / or realizable values ​​are (still) included. It can be provided that the valve mass flow interval is selected as a function of the control current interval, in particular because the valve mass flow interval can be (automatically) determined by selecting a control current interval. The pressure interval can be continuous or have a plurality (e.g. 20) different values. Preferably, for each pressure, in particular from the pressure interval, the valve mass flow can be determined as a function of the control current or a plurality of values ​​for the valve mass flow can be determined (each as a function of different control currents) (see figures). For example, the following can be provided:

[0022] Control current interval = [0.8 A, 1 .6 A], pressure interval = [10.5 bar, 18 bar].

[0023] Within the scope of the invention, it is optionally possible for the determination, by the control unit, of a rough mass flow estimate mdotH2rough as a function of the valve mass flow, to comprise fitting a fitting function, in particular a polynomial (preferably at least second, in particular third degree), to the valve mass flow, in particular as a function of the control current and / or the pressure of inflowing fuel.

[0024] It can be provided that for different pressures, e.g., for 20 equidistant values ​​in the pressure interval [10.5 bar, 18 bar], the valve mass flow is determined (e.g., during commissioning), measured, and / or simulated as a function of the control current. Accordingly, a functional relationship between valve mass flow and control current can be established for one (or each) pressure. The fitting can preferably be performed for one (or each) pressure or functional relationship between valve mass flow and control current. For example, the following function can be fitted:

[0025] For example, for printing Pi n H2Prpviv = 18 bar. For the control current i COThe measured and / or values ​​set (by the control unit) can be used for ntroi. The fitting parameters a4, a2, a3, a4, a5, a6, a7, a8 can be determined by the control unit, for example, by minimizing the root mean square (RMS). The fitting can preferably be carried out repeatedly for different pressures. In this case, removal, filtering, and / or restriction can be carried out beforehand. Accordingly, a fitting to the valve mass flow profile, in particular to the valve mass flow, can be carried out as a function of the control current. The filtered control current can preferably be used and / or a hysteresis component can be removed (or have been previously removed). The valve mass flow profile (as a function of the control current) can depend on the pressure of the incoming fuel.Preferably, a plurality of values ​​for pressure, valve mass flow, and / or control current can be measured and / or calculated during commissioning and / or through simulations. The results of the fitting can be stored in the control unit, in particular a memory unit, and / or retrieved later, in particular to determine a rough mass flow estimate as a function of a (set) control current.

[0026] Furthermore, it can be provided within the scope of the invention that the calculation, by the control unit, of a mass flow refinement m dotH2Re f ine depending on the rough mass flow estimate, depending on a (drawn) current i stck of the fuel cell system, in particular a stream of a fuel cell unit (stack) of the fuel cell system.

[0027] A further fitting can be performed, in particular to the rough mass flow estimate mdotH2rough (previously determined by fitting). The further fitting can include another polynomial, for example, at least of the second degree. The mass flow refinement m dotH2Re f ine can be dependent on the (drawn) current i stck of the fuel cell system and / or other fit parameters (e.g. b1, b2, b3, b4, b5, b6) are determined by the control unit, for example by minimizing the square deviation (RMS, residual mean square). Preferably, during commissioning and / or through simulations, a variety of values ​​for pressure, valve mass flow and / or control current can be measured and / or calculated. In this case, a mass flow refinement m dotH2Refine. The results of the further fitting can be stored in the control unit, in particular a memory unit, and / or retrieved later, in particular to achieve a mass flow refinement m dotH2Re f ine depending on a (set) control current.

[0028] With regard to the present invention, it is conceivable that the determination, by the control unit, of a mass flow m dotH2 of fuel by summing the coarse mass flow estimate mdotH2rough and the mass flow refinement mdotH2Refine.

[0029] Accordingly, the control unit can calculate the mass flow of fuel, in particular hydrogen, by

[0030] ^-dotH2 d otH2rough + ^-dotH2Refine

[0031] This can be determined for a specific pressure, particularly within the pressure interval. Thus, a precise fuel mass flow can be determined for each or a plurality of pressures. This determination allows for the influence of the fuel valve, which can particularly adjust the (possible) amount of incoming fuel, and the fuel cell unit or inverter / (drawn) current on the operation of the fuel cell system(s) to be taken into account. This allows for a more precise and / or fuel cell system-specific determination of the fuel mass flow.

[0032] Furthermore, it is conceivable that the determination of a mass flow of fuel by the control unit comprises clipping the mass flow of fuel, wherein, in particular, values ​​(for the final mass flow) below a minimum flow are set to zero and / or values ​​above a maximum flow are set to a maximum value. This can prevent inaccurate and / or undesired determination of values ​​in the boundary regions (of the above polynomials). The minimum flow and / or maximum flow can be specific to and / or identical to the limit values ​​or corner values ​​of the control flow interval. The maximum value can be a maximum mass flow, in particular a maximum possible mass flow of fuel, which is provided by the (maximally open) fuel valve (cf. Figs. 3 to 5, asymptotic saturation value top right).

[0033] Within the scope of the invention, it may be advantageous that, in particular after the determination, the fuel cell system is operated by the control unit as a function of the determination, in particular the mass flow of fuel.

[0034] Alternatively or additionally, it may be provided for the control unit to inform a user (e.g., a driver of a vehicle comprising the fuel cell system) and / or minimize fuel consumption, for example, by controlling and / or regulating the fuel cell system for this purpose. In other words, similar to consumption in a vehicle (fuel consumption), a mass flow of fuel (fuel consumption) can be determined and / or adjusted by appropriate operation.

[0035] The above object is achieved according to a second 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.

[0036] This results in the same advantages with respect to a computer program product according to the invention as have already been described with respect to a method according to the invention. According to a third aspect, the above object is achieved 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.

[0037] 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 and / or a computer program product according to the invention.

[0038] The above object is achieved according to a fourth 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.

[0039] The control unit can preferably be connected (via a respective data connection) in a data-communicating manner to the fuel valve, preferably the pressure sensor, a mass flow sensor, the fuel cell unit, and / or an inverter, thereby enabling, in particular, control (e.g., via control signals) by the control unit and / or transmission of data (e.g., sensor data, in particular, a drawn current, a control current, and / or a pressure) to the control unit.

[0040] 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 and / or a computer program product according to the invention and / or a computer-readable data carrier according to the invention.

[0041] The above object is achieved according to a fifth aspect by a fuel cell system according to the invention comprising a control unit according to the fourth aspect and / or a computer-readable data carrier according to the third aspect. The fuel cell system, in particular the control unit, can implement the method according to the first aspect and / or be configured therefor. The fuel cell system can preferably have a control unit according to the fourth aspect and / or a fuel valve through which in particular a fuel, preferably hydrogen, can be introduced into the fuel cell system. The fuel can preferably be guided via the fuel valve, e.g. via an anode path, to a fuel cell unit (e.g. a stack of fuel cells) of the fuel cell system.The fuel cell system, in particular the fuel cell unit, can generate a (drawn) current, for example via an inverter, which can preferably be controlled by the control unit to set a (target) current. It can be provided that the (drawn or actual) current is measured, in particular at and / or by the inverter, and then transmitted to the control unit, for example via a data connection. It can be provided that a pressure sensor is arranged on, in and / or near the fuel valve. This allows the pressure (of the fuel or at the fuel valve) to be determined.

[0042] This results in the same advantages with regard to a fuel cell system according to the invention as have already been described with regard to a method according to the invention and / or a computer program product according to the invention and / or a computer-readable data carrier according to the invention and / or a control unit according to the invention.

[0043] 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. In each case, schematically

[0044] Figure 1 a fuel cell system,

[0045] Figure 2 shows a method

[0046] Figure 3 a valve mass flow,

[0047] Figure 4 shows a valve mass flow, and Figure 5 shows a valve mass flow.

[0048] In the following figures, identical reference numerals are used for the same technical features, even for different embodiments.

[0049] Fig. 1 shows a fuel cell system 100 with a control unit FCCU, having a computing unit CU and a storage unit MU. The fuel cell system 100 comprises a fuel cell unit 101, which in particular can have an inverter (not shown). The fuel cell unit 101, in particular the inverter, can provide a (drawn) current i_Stck, which can be transmitted, for example, to a consumer, in particular to a drive device of a vehicle or a similar system. Fuel, e.g. hydrogen, can be introduced into the fuel cell system 100, in particular into the fuel cell unit 101, via a fuel valve 10. For this purpose, a pipe connection can be arranged between a fuel tank and the fuel cell unit 101.The fuel cell system 100 can have a pressure sensor 9, which is configured to determine the pressure p_lnH2PrpVlv (or different pressures p1, p2) on, in, and / or near the fuel valve 10. The pressure p_lnH2PrpVlv and / or the drawn current i_Stck can be transmitted (via a respective data connection) to the control unit FCCU, in particular to the computing unit CU. The control unit FCCU, in particular the computing unit CU, can control the fuel valve 10 and / or apply a control current i_control to it. This allows a valve mass flow m_dot_H2PrpVlv to be set. The control unit FCCU can preferably implement the method.

[0050] Fig. 2 shows a method for determining a mass flow m_dot_H2 of fuel, in particular hydrogen, for a fuel cell 100, in particular a proton exchange membrane fuel cell, comprising:

[0051] Determining 110, by a control unit FCCU, a valve mass flow m_dot_H2PrpVlv, which is specific for a fuel valve 10 of the fuel cell 100, Determining 120, by the control unit FCCU, a mass flow rough estimate m_dot_H2_rough as a function of the valve mass flow m_dot_H2PrpVlv,

[0052] Calculating 130, by the control unit FCCU, a mass flow refinement delta_m_dot_H2_Refine depending on the mass flow rough estimate m_dot_H2_rough and / or the current of the fuel cell system i_Stck,

[0053] Determining 140, by the control unit FCCU, a mass flow of fuel m_dot_H2 as a function of the mass flow rough estimate m_dot_H2_rough and the mass flow refinement delta_m_dot_H2_Refine.

[0054] It can be provided that the determination 110 of the valve mass flow m_dot_H2PrpVlv is carried out as a function of a pressure p_lnH2PrpVlv of inflowing fuel, in particular at the fuel valve 10.

[0055] It can be provided that the determination 110 of the valve mass flow m_dot_H2PrpVlv is carried out as a function of a control current i_control of the fuel valve 10, wherein in particular the opening of the fuel valve 10 is adjustable as a function of the control current i_control.

[0056] It can be provided that the determination 110 of the valve mass flow m_dot_H2PrpVlv comprises a filtering 111, in particular a low-pass filtering 111, of the control current i_control.

[0057] It can be provided that the determination 110 of the valve mass flow m_dot_H2PrpVlv comprises a removal 112 of a hysteresis part HA1, HA2 of the valve mass flow m_dot_H2PrpVlv, wherein the valve mass flow m_dot_H2PrpVlv has at least partially a hysteresis, comprising two hysteresis parts HA1, HA2, as a function of the control current i_control, and preferably during the removal 112 a hysteresis part HA2 is deleted, which is specific for an increasing control current i_control. It can be provided that the determination 110 of the valve mass flow m_dot_H2PrpVlv comprises a restriction 113 of the valve mass flow m_dot_H2PrpVlv to a valve mass flow interval m_dot_H2PrpVlv_l, and in particular a restriction 114 of the control current i_control to a control current interval i_control_l and / or the pressure p_lnH2PrpVlv to a pressure interval p_lnH2PrpVlv_l.

[0058] It can be provided that the determination 120, by the control unit FCCU, of a rough mass flow estimate m_dot_H2_rough as a function of the valve mass flow m_dot_H2PrpVlv, comprises a fitting 121 of a fitting function Fit, in particular a polynomial, to the valve mass flow m_dot_H2PrpVlv, in particular as a function of the control current i_control and / or the pressure p_lnH2PrpVlv of inflowing fuel.

[0059] It can be provided that the calculation 130, by the control unit FCCU, of a mass flow refinement delta_m_dot_H2_Refine is carried out as a function of the coarse mass flow estimate m_dot_H2_rough, as a function of a current i_Stck of the fuel cell system 100, in particular a current i_Stck of a fuel cell unit 101 of the fuel cell system 100.

[0060] It can be provided that the determination 140, by the control unit FCCU, of a mass flow of fuel m_dot_H2 is carried out by summing 141 the mass flow rough estimate m_dot_H2_rough and the mass flow refinement delta_m_dot_H2_Refine.

[0061] It can be provided that the determination 140, by the control unit FCCU, of a mass flow of fuel m_dot_H2 comprises a clipping 142 of the mass flow of fuel m_dot_H2, wherein in particular values ​​below a minimum flow i_Stck_Min are set to zero and / or values ​​above a maximum flow i_Stck_Max are set to a maximum value.

[0062] It can be provided that, in particular after the determination 140, an operation 150 of the fuel cell system 100 is carried out by the control unit FCCU as a function of the determination 140, in particular the mass flow of fuel m_dot_H2.

[0063] Fig. 3 shows, by way of example, a valve mass flow m_dot_H2PrpVlv as a function of a control current i_control, in particular for a first pressure p1 and a second pressure p2. The valve mass flow m_dot_H2PrpVlv can exhibit a hysteresis (cf. in particular for pressure p2), comprising a (left, first) hysteresis part HA1 (with decreasing control current i_control) and a (right, second) hysteresis part HA2 (with increasing control current i_control). It can be provided that the valve mass flow m_dot_H2PrpVlv is zero, in particular at a low control current, wherein, in particular, the fuel valve 10 is closed. At high control currents i_control, a maximum mass flow m_dot_H2_Max may be reached, which may be specific for the pressure p1 or p2, where in particular p2 may be > p1 (higher maximum mass flow m_dot_H2_Max at higher pressure p2).

[0064] Fig. 4, similar to Fig. 3, shows the removal 112 of a hysteresis component HA2, so that, in particular, only the hysteresis component HA1 remains. This enables a unique assignment of a valve mass flow m_dot_H2PrpVlv depending on the control current i_control.

[0065] Fig. 5 shows, by way of example and based on Fig. 4, a restriction 114 of the control current i_control and / or a restriction 113 of the valve mass flow m_dot_H2PrpVlv for the pressure p2, in particular to a control current interval i_control_l = [0.8, 1.6]. Starting from Fig. 5, the further method features can be carried out, in particular a determination 120 of a rough mass flow estimate m_dot_H2_rough, a fitting 121, a calculation 130 of a mass flow refinement delta_m_dot_H2_Refine, a determination 140 of a mass flow of fuel m_dot_H2, a summation 141, a clipping 142 and / or an operation 150, preferably in this order.

Claims

Claims 1. A method for determining a mass flow (m_dot_H2) of fuel, in particular hydrogen, for a fuel cell (100), in particular a proton exchange membrane fuel cell, comprising: Determining (110), by a control unit (FCCII), a valve mass flow (m_dot_H2PrpVlv) which is specific for a fuel valve (10) of the fuel cell (100), Determining (120), by the control unit (FCCII), a rough mass flow estimate (m_dot_H2_rough) as a function of the valve mass flow (m_dot_H2PrpVlv), Calculating (130), by the control unit (FCCII), a mass flow refinement (delta_m_dot_H2_Refine) depending on the rough mass flow estimate (m_dot_H2_rough), Determining (140), by the control unit (FCCII), a mass flow of fuel (m_dot_H2) as a function of the mass flow rough estimate (m_dot_H2_rough) and the mass flow refinement (d el ta_m_d ot_ H 2_ Ref ine) .

2. Method according to claim 1, characterized in that the determination (110) of the valve mass flow (m_dot_H2PrpVlv) is carried out as a function of a pressure (p_lnH2PrpVlv) of inflowing fuel, in particular at the fuel valve (10).

3. Method according to claim 1 or 2, characterized in that the determination (110) of the valve mass flow (m_dot_H2PrpVlv) is carried out as a function of a control current (i_control) of the fuel valve (10), wherein in particular the opening of the fuel valve (10) is adjustable as a function of the control current (i_control).

4. Method according to the preceding claim, characterized in that the determination (110) of the valve mass flow (m_dot_H2PrpVlv) comprises filtering (111), in particular low-pass filtering (111), of the control current (i_control).

5. Method according to one of the preceding claims, characterized in that the determination (110) of the valve mass flow (m_dot_H2PrpVlv) comprises a removal (112) of a hysteresis part (HA1, HA2) of the valve mass flow (m_dot_H2PrpVlv), wherein the valve mass flow (m_dot_H2PrpVlv) as a function of the control current (i_control) at least partially has a hysteresis comprising two hysteresis parts (HA1, HA2), and preferably during the removal (112) a hysteresis part (HA2) is deleted which is specific for an increasing control current (i_control) or a hysteresis part (HA1) is deleted which is specific for a decreasing control current (i_control).

6. Method according to one of the preceding claims, characterized in that determining (110) the valve mass flow (m_dot_H2PrpVlv) comprises limiting (113) the valve mass flow (m_dot_H2PrpVlv) to a valve mass flow interval (m_dot_H2PrpVlv_l), and in particular comprises limiting (114) the control current (i_control) to a control current interval (i_control_l) and / or the pressure (p_lnH2PrpVlv) to a pressure interval (p_lnH2PrpVlv_l).

7. Method according to one of the preceding claims, characterized in that the determination (120), by the control unit (FCCII), of a mass flow rough estimate (m_dot_H2_rough) as a function of the valve mass flow (m_dot_H2PrpVlv), a fitting (121) of a fitting function (Fit), in particular a polynomial, to the valve mass flow (m_dot_H2PrpVlv), in particular as a function of the control current (i_control) and / or the pressure (p_lnH2PrpVlv) of incoming fuel.

8. Method according to one of the preceding claims, characterized in that the calculation (130) by the control unit (FCCII) of a mass flow refinement (delta_m_dot_H2_Refine) is carried out as a function of the coarse mass flow estimate (m_dot_H2_rough) as a function of a current (i_Stck) of the fuel cell system (100), in particular a current (i_Stck) of a fuel cell unit (101) of the fuel cell system (100).

9. Method according to one of the preceding claims, characterized in that the determination (140), by the control unit (FCCII), of a mass flow of fuel (m_dot_H2) is carried out by summing (141) the mass flow rough estimate (m_dot_H2_rough) and the mass flow refinement (delta_m_dot_H2_Refine).

10. Method according to one of the preceding claims, characterized in that the determination (140) by the control unit (FCCII) of a mass flow of fuel (m_dot_H2) comprises a clipping (142) of the mass flow of fuel (m_dot_H2), wherein in particular values ​​below a minimum flow (i_Stck_Min) are set to zero and / or values ​​above a maximum flow (i_Stck_Max) are set to a maximum value.

11. Method according to one of the preceding claims, characterized in that, in particular after the determination (140), an operation (150) of the fuel cell system (100) is carried out by the control unit (FCCII) as a function of the determination (140), in particular the mass flow of fuel (m_dot_H2).

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 one of the preceding method claims.

13. A computer-readable data carrier in which instructions are stored which, when executed by a computer, cause the computer to perform the method according to one of the preceding method claims.

14. A 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), perform a method according to one of the preceding method claims.

15. Fuel cell system (100) comprising a control unit (FCCU) according to the preceding claim.

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