Method for operating a fuel cell system, control unit and fuel cell system

Abstract

The invention relates to a method for operating a fuel cell system having at least one fuel cell stack and at least one air system, in which at least one turbine and at least one bypass of the at least one turbine are arranged, the method comprises: detecting an operating mode of the fuel cell system which requires a loading, in particular a low loading or no loading, of the at least one turbine, obtaining a request to increase the loading of the at least one turbine, and determining the operating mode of the fuel cell system which requires a loading of the at least one turbine, in particular a low loading or no loading of the at least one turbine. Checking whether there is a need to drain a relevant path on at least one turbine, in particular upstream of the at least one turbine, preferably an exhaust gas cathode path, a turbine bypass path and / or a stack bypass path downstream of the at least one fuel cell stack, depending on the inspection, drainage and / or drying of the relevant path is performed.

Description

Technical Field

[0001] The invention relates to a method for operating a fuel cell system. The invention also relates to a computer program product, a control unit and a fuel cell system. Background Art

[0002] In vehicles (FCV, which stands for “Fuel Cell Vehicle” in English), in which the driving energy is also (primarily) provided by one (or more) fuel cell systems (FCS, which stands for “Fuel Cell System” in English), oxygen from the ambient air is usually used as an oxidant in order to react with hydrogen in the fuel cell to form water (or water vapor) and thus provide electrical power by electrochemical conversion.

[0003] Ambient air is supplied to the fuel cell stack by means of an air delivery system or an air compression system. For this purpose, a correspondingly variable air mass flow and a corresponding pressure level are required.

[0004] The compression (compression) of the air usually takes place via a thermofluid machine which is driven in the form of an electric motor (EAC, which stands for “electric driven air compressor” in English).

[0005] Optionally, for air compression (single-stage or multi-stage), energy recovery of the outflowing moist air can be achieved with the aid of a turbine (e.g. an electrically driven turbocharger EACT or a turbocharger TAC without an electric drive, also referred to as an exhaust gas turbocharger ATL). The exhaust gas enthalpy is used in order to drive the compressor wheel with the aid of the turbine.

[0006] The turbine is loaded with fluid from the moist exhaust gas of the cathode stack. This fluid may also contain liquid water (water droplets, water waves, etc.). This may damage the turbine.

[0007] The known solution A can provide for the use of a water separator downstream of the stack (cathode) and upstream of the turbine in order to protect the turbine against damage / degradation.

[0008] The known concept B can provide for the use of a gas-gas heat exchanger (GGHx) which cools the intake air with the help of the exhaust gas and thereby additionally provides exhaust gas enthalpy upstream of the turbine and thus increases the turbine power. By warming the exhaust gas, the humidity can be reduced and / or water droplets can be converted into a vapor state. Summary of the invention

[0009] The present invention provides a method for operating a fuel cell system. In addition, the present invention provides a corresponding computer program product, a corresponding control unit and a corresponding fuel cell system. Here, the features and details described in the context of different embodiments and / or aspects of the present invention are of course also applicable in the context of other embodiments and / or aspects according to the present invention, and vice versa, so that the disclosure content of the individual embodiments and / or aspects always refers to each other or can refer to each other.

[0010] According to a first aspect, the present invention provides: a method for operating a fuel cell system (100), the fuel cell system having at least one fuel cell stack (101) and at least one air system (10), in which at least one turbine (Turb) and at least one bypass of the at least one turbine (Turb) (e.g. a turbine bypass path, or other bypasses, such as exhaust gas recirculation and / or exhaust gas transfer or the like for use in other systems) are arranged.

[0011] The method comprises the following steps:

[0012] - detecting an operating mode of the fuel cell system which requires a load on the at least one turbine, in particular a low load or no load on the at least one turbine (for example less than 15% or 8% of the total exhaust gas flow),

[0013] - receiving, in particular proactively receiving, a request to increase the loading of at least one turbine,

[0014] - checking whether there is a need to drain relevant paths on the at least one turbine, in particular upstream of the at least one turbine, preferably the exhaust gas cathode path, the turbine bypass path and / or the stack bypass path downstream of the at least one fuel cell stack,

[0015] - Based on said checking, drainage and / or drying of the relevant paths is performed.

[0016] The steps of the method can be performed in a predetermined sequence or in a changed sequence. The steps of the method can be performed synchronously, at least partially simultaneously and / or successively.

[0017] Preferably, the fuel cell system (or simply system) can be used for mobile applications, for example in vehicles, in particular fuel-driven vehicles, preferably in the field of commercial vehicles with high service life requirements. The fuel cell system can be used as a main energy supplier for the vehicle. In addition, the fuel cell system in the sense of the present invention can be used as an energy supply for auxiliary drives and / or power drives of vehicles, for example hybrid vehicles. However, the fuel cell system can also be used for stationary applications, for example in generators.

[0018] The fuel cell system may have a plurality of fuel cell stacks (or simply referred to as stacks), each of which has a plurality of stacked fuel cells and functional systems associated therewith, the functional systems comprising: a medium system (air system or cathode system, fuel system or anode system, cooling system) and an electrical system. Preferably, the fuel cell system may include a plurality of modules, each of which is in the form of a single stack of a plurality of stacked fuel cells.

[0019] The present invention recognizes that the exhaust fluid contains liquid water, which can accumulate upstream of the turbine and in the turbine and wet surfaces, so that, in particular at low temperatures, due to condensation, water can accumulate upstream of the turbine and / or in the turbine and / or can strongly wet surfaces of the turbine.

[0020] This can also take place between the droplet separator and the turbine (in the case of known variant A). If the gas-gas heat exchanger (in the case of known variant B) is cold and has not yet warmed up, in this case no pretreatment of the exhaust gas takes place (no evaporation of water).

[0021] Therefore, in the cold case, the fluid flow mostly passes by the turbine.When switching to a higher load point with loading on the turbine, the liquid water can come onto the turbine in waves and / or droplets.

[0022] The present invention is directed to these situations.

[0023] The proposed method can be used to carry out a drain process that meets the requirements. The drain process enables drainage of relevant paths on at least one turbine, in particular upstream of the turbine, such as the exhaust gas cathode path downstream of at least one fuel cell stack, the turbine bypass path upstream of the turbine and / or the stack bypass path upstream of the turbine.

[0024] The proposed method can be executed between the operating mode (op1) and the operating mode (op2) or in other words when switching from the operating mode (op1) to the operating mode (op2):

[0025] op1: operation with fluid loading of the turbine bypass path without significantly loading the turbine path,

[0026] Then,

[0027] OP2: Significant fluid loading of the turbine path.

[0028] By means of a drainage process adapted to the requirements, liquid water which has accumulated or condensed on the turbines, in particular in the relevant path upstream of at least one turbine, can be discharged to the environment before the turbines are seriously subjected to fluid.

[0029] In particular, this drainage process can be advantageous after certain operating modes in which a low pressure (eg close to ambient pressure) is required in the stack, so that the air system is operated with an open or approximately open turbine bypass valve (ByT).

[0030] This is the case in particular in the case of freezing starts and in the case of cold starts, but it can also occur in start-stop phases, after waiting, when driving in traffic jams, when driving downhill and in cold operating conditions.

[0031] With this approach, several important advantages can be achieved:

[0032] - component protection of the turbine (e.g. turbine impeller, rotor bearings, turbine-compressor shaft) and other components in the exhaust gas path,

[0033] οPrevent droplet impact,

[0034] οPrevent water waves,

[0035] o prevent damage,

[0036] ο prevent degradation,

[0037] - Defined operating conditions during the switchover lead to improved functionality.

[0038] If a low pressure, in particular a low pressure close to the ambient pressure, is requested in at least one fuel cell stack, so that the air system is operated with an open or approximately open turbine bypass valve, an operating mode of the fuel cell system can be generated that requires loading, in particular low loading or no loading of the at least one turbine. In this case, when switching to a higher load point with loading of the turbine, liquid water can flow to the turbine in waves and / or droplets. Advantageously, the method can make it possible to carry out a drainage process that meets the requirements before switching to a higher load point with loading of the turbine, which drainage process can make it possible to drain the relevant paths on the at least one turbine.

[0039] An operating mode of the fuel cell system which requires loading of the at least one turbine, in particular low loading or no loading of the at least one turbine, may include at least one of the following operating modes which may also include cold operating conditions:

[0040] - Frozen start,

[0041] - Cold start,

[0042] - Stop-start operation, e.g. in traffic jams and / or city driving,

[0043] - idling operation, e.g. when driving downhill,

[0044] - low partial load operation, e.g. when driving downhill,

[0045] - Operation after standby, e.g. when driving downhill,

[0046] - Diagnostics run, and / or

[0047] - Regeneration operation.

[0048] The request to increase the load on at least one turbine can provide for an increase in pressure and / or an increase in mass flow in the fuel cell system, which can result in a significant fluid load on the turbine path.

[0049] In particular, a request to increase the loading of the at least one turbine can be provided when switching into at least one of the following operating modes:

[0050] - medium part load operation,

[0051] - high load operation, and / or

[0052] - Full load operation.

[0053] When checking whether there is a need to drain the relevant path on the at least one turbine, a plurality of information can be advantageously taken into account, which information can include, for example, at least one of the following information:

[0054] - past load curves,

[0055] - the temperature in the relevant path on at least one turbine,

[0056] - determining, in particular estimating, the amount of condensed water in the relevant path on at least one turbine,

[0057] - determining, in particular estimating, the risk and / or amount of water accumulation in the relevant path on at least one turbine,

[0058] - determining, in particular estimating, a risk of droplet impingement on at least one turbine and / or a risk of degradation of at least one turbine, and / or

[0059] - the previous operating mode,

[0060] For example, if drying and / or draining has been performed recently, there is no need to perform new draining and / or drying.

[0061] And / or wherein a model calculation is performed during the checking.

[0062] In this way, the need for drainage and / or drying can be determined so that the drainage process is carried out in accordance with the need.

[0063] The execution of drainage and / or drying (or drainage process) can be performed in dependence on the topology. For this purpose, different bypass routes of the turbine can be utilized, which can differ depending on the topology. For example, a turbine bypass path can be used to perform drainage and / or drying.

[0064] Advantageously, when performing drainage and / or drying, at least one of the following actions may be performed:

[0065] - opening and / or keeping open a turbine bypass and / or a turbine bypass path,

[0066] - loading the air compression system with a higher load point so that preferably more mass flow passes through the relevant path,

[0067] - at least partially opening the stack bypass path,

[0068] - Adjustment of the stacking operating point, for example a temporary adjustment of a LambaCath.

[0069] In this way, an increase in the air mass flow in the relevant path can be achieved. By increasing the air mass flow in the relevant path, the flow velocity can be increased, whereby liquid water can be better discharged from the fluid path.

[0070] Additionally, the method may include:

[0071] - providing a license for increasing the loading of at least one turbine.

[0072] In this way, permission can be achieved for safely switching to a higher load point with loading of the turbine, since the drainage process has been carried out in accordance with the requirements.

[0073] Additionally, the method may include:

[0074] An increase in the loading of at least one turbine is carried out.

[0075] This embodiment makes it possible to increase, in particular significantly increase, the flow of fluid through the at least one turbine. This embodiment makes it possible to reduce the cross section of the turbine bypass and / or the turbine bypass path.

[0076] Advantageously, the increase in the loading of the at least one turbine can be carried out with low dynamics, for example in a time range of 0.5 to 1 second, wherein fast dynamics, for example in a time range of 0.05 to 0.1 second, are possible. In this way, a stable flow can be created. In this way, the risk of droplet impacts / water waves can be reduced. In this way, loads on the system, such as pressure pulses, loads on the rotor, etc., can be reduced.

[0077] This embodiment can be implemented such that the operating point for the air compression system is adjusted additionally, in particular in parallel or sequentially, preferably in conjunction with a request to increase the loading of the at least one turbine.

[0078] This embodiment can be implemented such that the mass flow present in the step (draining and / or drying the relevant paths according to the check) is converted into a mass flow request for the step (operating the fuel cell system with increased loading of the at least one turbine).

[0079] This embodiment can be implemented such that the pressure present in the step (draining and / or drying the relevant paths according to the check) is converted into a pressure request for the step (operating the fuel cell system with increased loading of the at least one turbine).

[0080] Additionally, the method may include:

[0081] In particular, in response to the request, the fuel cell system is operated with an increased load on the at least one turbine.

[0082] In this case, safe operation of the fuel cell system with increased loading of the at least one turbine can be achieved, since the drainage process is already carried out in accordance with the requirements.

[0083] According to another aspect, the invention provides a computer program product comprising instructions which, when implemented by a computer (e.g. a computing unit of a control unit), cause the computer to perform a method which can be run in the manner described above. With the aid of the computer program product, the same advantages as those described above in the context of the method according to the invention can be achieved. In the present case, these advantages are fully cited.

[0084] A corresponding control unit provides another aspect of the invention. In the memory unit of the control unit a computer program in the form of a code can be stored, which, when executed by the computing unit of the control unit, executes a method that can be run in the manner described above. With the aid of this control unit, the same advantages as those described above in the context of the method according to the invention can be achieved. In the present case, these advantages are fully cited.

[0085] A corresponding fuel cell system with a corresponding control unit provides another aspect of the invention. With this fuel cell system, the same advantages as those described above in the context of the method according to the invention can be achieved. In the present case, these advantages are fully cited. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] The present invention and its extensions and advantages are described in more detail below with reference to the accompanying drawings. The accompanying drawings schematically show:

[0087] Figure 1 An exemplary system topology is shown.

[0088] Figure 2 shows another exemplary system topology, and

[0089] Figure 3 An exemplary sequence of a method within the meaning of the present invention is shown.

[0090] In the various figures, identical components of the invention are always provided with the same reference symbols, so that these components are generally only described once. DETAILED DESCRIPTION

[0091] Figures 1 to 3 , especially Figure 3, used to explain a method developed for operating a fuel cell system 100, which has a fuel cell stack 101 and at least one air system 10, in which at least one turbine Turb and at least one bypass of the at least one turbine Turb are provided (for example, a turbine bypass path T2, or other bypasses, such as an exhaust gas recirculation portion and / or an exhaust gas transfer portion or the like for use in other systems).

[0092] like Figure 3 As shown, the method includes:

[0093] detecting 10 an operating mode op1 of the fuel cell system 100 which requires a load on the at least one turbine Turb, in particular a low load or no load on the at least one turbine,

[0094] - obtaining 20, in particular prospectively obtaining, a request to increase the load on at least one turbine Turb,

[0095] - a check 30 is made as to whether there is a need to drain the relevant path on at least one turbine Turb, said path being Figure 1 and 2 Indicated by dotted lines,

[0096] The relevant path is in particular upstream of at least one turbine Turb, and the relevant path is preferably an exhaust gas cathode path, a turbine bypass path and / or a stack bypass path downstream of at least one fuel cell stack 101,

[0097] - Based on said checking, a drainage and / or drying of the relevant paths is performed 40 (summarized as a drainage process).

[0098] The proposed method is used to carry out a required drainage process in step 40, which enables drainage of the relevant fluid paths on at least one turbine Turb, in particular upstream of at least one turbine Turb (see Figure 1 and 2 The relevant fluid paths are, for example, the exhaust gas cathode path downstream of at least one fuel cell stack 101, the turbine bypass path T2 upstream of at least one turbine Turb and / or the stack bypass path ByPath upstream of the turbine Turb.

[0099] The proposed method can be executed between the operating mode op1 and the operating mode op2 or in other words when switching from the operating mode op1 to the operating mode op2:

[0100] op1: operation with fluid loading of the turbine bypass path T2 without significantly loading the turbine path T1,

[0101] Then,

[0102] op2: Significant fluid loading of turbine path T1.

[0103] By means of a drainage process as required, liquid water which has accumulated or condensed in the relevant path of at least one turbine, in particular upstream of at least one turbine, can be discharged to the environment Env before the turbine Turb is seriously loaded with fluid.

[0104] In particular, this drainage process can be advantageous after a certain operating mode in which a low pressure (eg close to ambient pressure) is required in the stack 101 , so that the air system 10 is operated here with an open or approximately open turbine bypass valve ByT.

[0105] This is the case in particular in the case of freezing starts and in the case of cold starts, but it can also occur in start-stop phases, after waiting, when driving in traffic jams, when driving downhill and in cold operating conditions.

[0106] With this approach, several important advantages can be achieved:

[0107] - Turbines (e.g. turbine impellers, rotor bearings, turbine-compressor shafts)

[0108] and other components in the exhaust gas path,

[0109] οPrevent droplet impact,

[0110] οPrevent water waves,

[0111] o prevent damage,

[0112] ο prevent degradation,

[0113] - Defined operating conditions during the switchover lead to improved functionality.

[0114] exist Figure 1 1 shows an exemplary fuel cell system 100 having an air system 10 for supplying oxygen to one or more stacks 101. The air system 10 comprises a single-stage compressor Comp (EACT, which stands for “electric driven air compressor with turbine” in English) with a turbine Turb.

[0115] Figure 1 The topologies shown are exemplary only.

[0116] The air system 10 comprises:

[0117] a turbine path T1 comprising a turbine Turb for regenerating energy from the exhaust gas L2,

[0118] and

[0119] A turbine bypass path T1 , which contains an adjustable valve / throttle flap.

[0120] Furthermore, the air system 10 comprises a gas-gas heat exchanger GGHx for cooling the intake air L1 by means of the exhaust air L2. A stack bypass path ByPath is provided in the air system 10. Optionally, the air system 10 can be equipped with a humidifier BF.

[0121] The turbine bypass valve ByT can be used for pressure control and, if necessary, also participate in mass flow control.

[0122] In some operating modes of the system 100, in particular for the frozen start method and the cold start method, a low pressure (close to the ambient pressure) is required in the stack 101, so the air system 10 is operated here with an open or approximately open turbine bypass valve ByT. Here, the turbine Turb is mostly bypassed, or a small flow (e.g. <15%) flows in the turbine path T1 and a very large flow (e.g. >85%) flows in the turbine bypass path T2.

[0123] In other operating scenarios (in addition to the start method), operation with op1 can also be carried out periodically, for example in a start-stop phase, after a standstill, when driving in a traffic jam, when driving downhill and in cold operating conditions.

[0124] The small proportion of the exhaust gas mass flow in the turbine path, combined with low pressures and pressure differences (low flow velocities) and low rotational speeds of the rotor (compressor-turbine shaft W), is initially not critical for the turbine wheel in terms of droplet impacts, etc.

[0125] However, at these operating points, water can accumulate in the area of ​​the exhaust gas path and possibly in other paths (stack bypass path ByPath, turbine bypass path T2) and / or significantly wet surfaces upstream of the turbine and / or in the turbine Turb (see area indicated by means of dotted lines), which water can then - in the event of sudden load changes or during switching or in the event of significant fluid loading on the turbine path T1 - trigger significant droplet impacts or water waves on the turbine Turb and can thereby lead to significant degradation, reduced service life or even damage (e.g. bearing damage due to deflection of the rotor).

[0126] The method avoids this by carrying out a drainage process for discharging water before the turbine path T1 is significantly loaded.

[0127] Figure 2 An exemplary fuel cell system 100 is shown, which has an air system 10 for supplying oxygen to a plurality of stacks 101. The air system 10 is designed with two turbines Turb1, Turb2 and two turbine bypass paths T2.

[0128] Figure 2 The topologies shown are exemplary only.

[0129] The air system 10 comprises:

[0130] two turbine paths T1 , each having a turbine Turb1 , Turb2 for regenerating energy from the exhaust gas L2 ,

[0131] and

[0132] Two turbine bypass paths T2 , each of which has an adjustable turbine bypass valve ByT1 , ByT2 or an adjustable throttle flap.

[0133] Furthermore, the air system 10 comprises two gas-gas heat exchangers GGHx1, GGHx2 for cooling the intake air L1 by means of the exhaust gas L2. A stack bypass path ByPath is provided in the air system 10. Alternatively, the air system 10 may be configured with an intercooler IC.

[0134] In the case of op1 , both turbine bypass paths T2 may be open / mostly open (large flow cross-section openings).

[0135] Furthermore, in the case of op2, the turbine bypass valves ByT1, ByT2 can be used for pressure regulation and / or mass flow regulation.

[0136] As combined Figure 1As already described, here, after operation with an open or substantially open turbine bypass path T2, negative effects may also occur when switching to a significant fluid loading of the turbine path T2 due to droplet impacts, water splashes or the like. In the case of corresponding operating modes or operating conditions, the surfaces and paths that can be wetted by liquid water or are subject to water accumulation are even significantly larger here (see the marked areas).

[0137] Here too, the method according to the invention can be used in order to carry out a targeted drainage process, in particular before a significant loading of the turbine path T1 occurs.

[0138] Except in Figure 1 and Figure 2 In addition to the example shown in FIG. 1 , further topologies can be provided which have different windings of the turbine Turb.

[0139] The request 20 for increasing the load on at least one turbine (Turb) can be provided to increase the pressure and / or increase the mass flow in the fuel cell system (100). The request for increasing the load on at least one turbine (Turb) can be generated when switching to at least one of the following operating modes:

[0140] - medium part load operation,

[0141] - high load operation, and / or

[0142] - Full load operation.

[0143] When checking 30 whether there is a need to drain the relevant path on at least one turbine Turb, a number of items of information can advantageously be taken into account in step 32:

[0144] - past load curves,

[0145] - the temperature in the relevant path on at least one turbine Turb,

[0146] - determining, in particular estimating, the amount of condensed water in the relevant path on at least one turbine Turb,

[0147] - determining, in particular estimating, the risk and / or amount of water accumulation in the relevant path on at least one turbine Turb,

[0148] - determining, in particular estimating, the risk of droplet impact on at least one turbine Turb and / or

[0149] or the risk of degradation of at least one turbine,

[0150] and / or

[0151] - the previous operating mode,

[0152] For example, if drying and / or draining has already been carried out recently, there is no need to carry out new draining and / or drying.

[0153] When checking 30 whether there is a need to drain relevant paths on at least one turbine Turb, a model calculation can be performed.

[0154] When carrying out 40 the drainage process, ie the drainage and / or drying, the existing bypass of the at least one turbine Turb can be utilized, which bypass can specifically differ in terms of topology. Preferably, the turbine bypass path T2 can be used to carry out 40 the drainage and / or drying.

[0155] When performing the excretion process 40, the following actions may be performed:

[0156] - opening and / or keeping open 42 the turbine bypass ByT and / or the turbine bypass path T2,

[0157] - loading 44 the air compression system with a higher load point so that preferably more mass flow passes through the relevant path,

[0158] - at least partially opening 46 the stacking bypass path,

[0159] - Adjustment 48 of the stacking operating point, for example a temporary adjustment of a LambaCath, for example.

[0160] like Figure 3 As shown, the method may further include:

[0161] A permission 50 is provided for increasing the loading of at least one turbine Turb.

[0162] like Figure 3 As shown, the method may further include:

[0163] - An increase in the load on the at least one turbine Turb is carried out 55 .

[0164] The embodiment 55 can be implemented such that the flow of fluid through the at least one turbine Turb is increased, in particular significantly increased. The embodiment 55 can be implemented such that a reduction in the cross section of the turbine bypass T2 and / or the turbine bypass path T2 is carried out.

[0165] Advantageously, the increase in the loading of at least one turbine Turb can be performed with low dynamics, for example in a time range of 0.5 to 1 second, wherein fast dynamics, for example in a time range of 0.05 to 0.1 second, are possible. In this way, a stable flow can be constructed. In this way, the risk of droplet impact / water waves can be reduced. In this way, loads in the system 100, such as pressure pulses, loads on the rotor, etc., can be reduced.

[0166] The implementation 55 can be implemented such that the operating point for the air compression system is adjusted additionally, in particular in parallel or sequentially, preferably in conjunction with the request 20 for increasing the load on the at least one turbine Turb.

[0167] Implementation 55 can be implemented in such a way that the mass flow present in step 40 is converted into a mass flow request for step 60 .

[0168] Implementation 55 can be implemented in such a way that the pressure present in step 40 is converted into a pressure request for step 60 .

[0169] Additionally, this method can set:

[0170] - in particular in response to the request (20), operating (60) the fuel cell system (10) with an increased load on the at least one turbine (Turb).

[0171] A corresponding computer program product, a corresponding control unit ecu and a corresponding fuel cell system 100 with a corresponding control unit ecu are further aspects of the invention.

[0172] The above description of the embodiments only describes the present invention in the scope of examples. Of course, as long as it is technically reasonable, the individual features of the embodiments can be freely combined with each other without leaving the framework of the present invention.

Claims

1. A method for operating a fuel cell system (100), the fuel cell system having at least one fuel cell stack (101) and at least one air system (10), in which at least one turbine (Turb) and at least one bypass of the at least one turbine (Turb) are arranged, The method comprises: - detecting (10) an operating mode (op1) of the fuel cell system (100) which requires a load on the at least one turbine (Turb), in particular a low load or no load on the at least one turbine, - obtaining (20), in particular prospectively obtaining, a request to increase the load on the at least one turbine, - checking (30) whether there is a need to drain the relevant path on the at least one turbine (Turb), The relevant path is in particular upstream of the at least one turbine (Turb), the relevant path is preferably an exhaust gas cathode path, a turbine bypass path and / or a stack bypass path downstream of the at least one fuel cell stack (101), - Based on said checking, performing (40) drainage and / or drying of the relevant path.

2. The method according to claim 1, in, An operating mode of the fuel cell system (100) requires loading of the at least one turbine (Turb), in particular a low loading or no loading of the at least one turbine, and the operating mode requires a low pressure in the at least one fuel cell stack (101), in particular a low pressure close to the ambient pressure, so that the air system (10) is operated with an open or approximately open turbine bypass valve (ByT).

3. The method according to claim 1 or 2, in, An operating mode of the fuel cell system (100) requires loading of the at least one turbine (Turb), in particular low loading or no loading of the at least one turbine, and includes at least one of the following operating modes, which can also include cold operating conditions: - Frozen start, - Cold start, - Start-stop operation, - idling operation, - low part load operation, - Operation after standby, - Diagnostics run, and / or - Regeneration operation.

4. The method according to any one of the preceding claims, in, The request to increase the load on the at least one turbine is provided by increasing the pressure and / or increasing the mass flow in the fuel cell system (100), and / or Therein, a request to increase the load on the at least one turbine is provided when switching to at least one of the following operating modes: - medium part load operation, - high load operation, and / or - Full load operation.

5. The method according to any one of the preceding claims, in, During the checking (30), a plurality of information, in particular at least one of the following information, is taken into account (32): - past load curves, - the temperature in the relevant path on the at least one turbine (Turb), - determining, in particular estimating, the amount of condensed water in the relevant path on the at least one turbine, - determining, in particular estimating, the risk and / or amount of water accumulation in the relevant path on the at least one turbine, - determining, in particular estimating, a risk of droplet impingement on the at least one turbine and / or a risk of degradation of the at least one turbine, and / or - the previous operating mode, And / or wherein a model calculation is performed during the checking (30).

6. The method according to any one of the preceding claims, in, performing drainage and / or drying in dependence on the topology (40), and / or Wherein, when performing (40) draining and / or drying, at least one of the following actions is performed: - opening and / or keeping open (42) the turbine bypass (ByT) and / or the turbine bypass path (T2), - loading (44) the air compression system at a higher load point so that preferably more mass flow passes through the relevant path, - at least partially opening (46) the stack bypass path, - Adjust (48) the stacking operating point.

7. The method according to any one of the preceding claims, The method further comprises: - providing a license (50) for increasing the loading of the at least one turbine (Turb).

8. The method according to any one of the preceding claims, The method further comprises: - carrying out (55) increasing the load on the at least one turbine (Turb), In particular, The flow of the fluid through the at least one turbine is increased, in particular significantly increased, and / or causing a reduction in the cross section of the turbine bypass (ByT) and / or of the turbine bypass path (T2) to be performed, and / or additionally, in particular in parallel or sequentially, preferably in conjunction with the request (20), an operating point for the air compression system is adjusted, and / or so that the mass flow existing in step (40) is converted into a mass flow request for step (60), and / or The pressure present in step (40) is converted into a pressure request for step (60).

9. The method according to any one of the preceding claims, The method further comprises: - operating (60) the fuel cell system (10) with an increased load on the at least one turbine.

10. The method according to any one of the preceding claims, in, The method is performed in a predictive manner so that drainage and / or drying is performed proactively.

11. A computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to execute the method according to any one of the preceding claims. 12 . A control unit (ecu) having a computing unit and a memory unit, in which a code is stored which, when at least partially executed by the computing unit, executes the method according to claim 1 .

13. A fuel cell system (100) comprising a control unit (200) according to the preceding claim.

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