DE102023203567A1 - Method for operating a fuel cell system, control unit and fuel cell system - Google Patents

Abstract

The invention relates to a method for operating a fuel cell system (100) with at least one fuel cell stack (101) and at least one cathode system (10), wherein the at least one cathode system (10) has a plurality of valves and/or throttle valves (VIV), comprising at least one throttle valve (VLVTO) with a control function and/or a shut-off function, preferably with a sealing effect, characterized in that, if the at least one throttle valve (VLVTO) has a conflict of objectives between dynamics and tightness when controlling the at least one throttle valve (VLVTO), the operation of the at least one fuel cell stack (10) is switched between the dynamic operating mode (opR) and the tight-closing operating mode (opD) of the at least one throttle valve (VLVTO), in order in particular to optimize an efficiency, a degree of effectiveness and/or a consumption of the fuel cell system (100).

Description

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.

State of the art

In drive systems with fuel cell systems, oxygen from the ambient air is usually used to react with hydrogen in the fuel cell to form water or water vapor and thus generate electrical energy. The ambient air is fed to the fuel cell stack using a conveyor system or compression system. The compression system is designed to provide a specific air mass flow and/or a specific pressure level. The compression or compression of the air often takes place using a thermal flow machine (single-stage, multi-stage or multi-flow). In addition to air compression, energy can be recovered from the outflowing moist air using a turbine (e.g. electrically driven turbocharger or turbocharger without electric drive). Higher system pressures (e.g. to enable high-performance fuel cell systems) can be achieved using two-stage compression and energy recuperation using a turbine.

Fuel cell systems comprise at least one or more fuel stacks. Valves, usually in the form of throttle valves, are used to regulate the air mass flow and the pressure in the fuel stack or in the multiple fuel stacks (for a multi-stack system). In addition, throttle valves - provided they can have a tight-closing effect - can also be used for operating modes: start, stop, start-stop, bleed-down, standstill, etc., in order to protect the fuel stack(s) from the ingress of atmospheric oxygen.

disclosure of the invention

According to the first aspect, the invention provides a method for operating a fuel cell system with the features of the independent method claim. Furthermore, according to the second aspect, the invention provides a computer program product with the features of the independent product claim, according to the third aspect, a control unit with the features of the independent device claim, and according to the fourth aspect, a fuel cell system with the features of the independent system claim. Further features, advantages and details of the invention emerge from the subclaims, the description and the drawings. Features and details that are described in connection with individual aspects of the invention naturally also apply in connection with the other aspects of 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.

The present invention provides: a method for operating a fuel cell system (or system for short) with at least one (or more) fuel cell stack(s) (or stack or stacks for short) and at least one (e.g. one each or one common for several stacks) cathode system,
wherein the at least one cathode system has a plurality of valves and/or throttle valves,
comprising at least one (or more) throttle valve(s) with a control function and/or a shut-off function, preferably with a sealing effect,
characterized by
that, if the at least one throttle valve has a conflict of objectives between dynamics and tightness when controlling the at least one throttle valve, the operation of the at least one fuel cell stack is switched between the dynamic operating mode and the tight-closing operating mode of the at least one throttle valve in order to optimize in particular an efficiency, a degree of effectiveness and/or a consumption of the fuel cell system.

The fuel cell system within the scope of the invention can have at least one or more fuel cell stacks, so-called fuel cell stacks or, in short, stacks, each with several stacked repeat units in the form of fuel cells, e.g. PEM fuel cells.

The fuel cell system within the scope of the invention can advantageously be used for mobile applications, such as in motor vehicles, or for stationary applications, such as in generator systems.

The fuel cell system within the scope of the invention can advantageously have a control unit which is used to control the cathode system, in particular to control a compression unit of the cathode system and preferably to control the valves and/or throttle valves, preferably to control the at least one throttle valve with a control function and/or a shut-off function, preferably with a sealing function. k, carried out according to the method according to the invention.

The cathode system within the scope of the invention can also be referred to as an air system.

The compression unit within the scope of the invention can also be referred to as an air compression system. The compression unit within the scope of the invention can have at least one or more compressors, wherein in particular at least one compressor can be driven electromotively, for example with the aid of an electric motor, and/or at least one compressor can be driven fluidically, preferably with the aid of a turbine or a turbocharger. At least one compressor can also be designed as a single-stage, two-stage or two-flow compressor. Furthermore, the compression unit can have at least one turbine to support at least one compressor.

1. 1. eine Drosselklappe (sog. ByTurb) in einem Bypass einer Turbine im Abgaspfad eines Brennstoffzellensystems,
2. 2. eine Drosselklappe (sog. ByCath) in einem Bypass eines Stack-Kathodenpfades,
3. 3. eine Drosselklappe (sog. ByEGR) in einem AGR/EGR -Pfad (Abgasrückführung / eng. „exhaust gas recirculation“),
4. 4. eine Drosselklappe stromaufwärts eines Kathoden-Einlasses des jeweiligen Stacks, d. h. in einem (Haupt-)Kathodenpfad,
5. 5. eine Drosselklappe stromabwärts eines Kathoden-Auslasses des jeweiligen Stacks, d. h. im (Haupt-)Kathodenpfad,
6. 6. eine Drosselklappe (sog. ByComp) in einem Bypass zu einem Verdichter,
7. 7. eine Drosselklappe (sog. ByEGT) in einem Abgastransferpfad (EGT=„exhaust gas transfer“), durch die ein Teil des Abgases eines Stacks in den Zuluftpfad eines anderen Stacks geleitet werden kann,
8. 8. eine Drosselklappe (sog. ByHumid) in einem Bypass eines Befeuchters,
9. 9. eine Drosselklappe an weiteren/anderen Stellen eingesetzt werden, usw.

The at least one throttle valve within the scope of the invention can preferably have both a control function and a shut-off function with a sealing effect. Such throttle valves can, for example:

1. 1. a throttle valve (so-called ByTurb) in a bypass of a turbine in the exhaust path of a fuel cell system,
2. 2. a throttle valve (so-called ByCath) in a bypass of a stack cathode path,
3. 3. a throttle valve (so-called ByEGR) in an EGR/EGR path (exhaust gas recirculation),
4. 4. a throttle valve upstream of a cathode inlet of the respective stack, ie in a (main) cathode path,
5. 5. a throttle valve downstream of a cathode outlet of the respective stack, ie in the (main) cathode path,
6. 6. a throttle valve (so-called ByComp) in a bypass to a compressor,
7. 7. a throttle valve (so-called ByEGT) in an exhaust gas transfer path (EGT), through which part of the exhaust gas from one stack can be directed into the supply air path of another stack,
8. 8. a throttle valve (so-called ByHumid) in a bypass of a humidifier,
9. 9. a throttle valve can be used in other/different locations, etc.

The invention particularly addresses the throttle valves where leaks lead to a loss of efficiency in the system, i.e., in particular throttle valves 1, 2, 3,6 and 7.

• - Der dichtschließende Betriebsmodus wurde bisher (nach Stand der Technik) bspw. bei manchen Drosselklappen für die Betriebszustände Start-Stopp, Start, Stopp, Bleed-down Stillstandsphasen usw. des Stacks eingesetzt werden, bei denen der jeweilige Stack nicht aktiv elektrische Leistung liefern soll. Erfindungsgemäß wird der dichtschließende Modus nun aber auch zur Erreichung der beschriebenen Ziele (Verbrauch, Energieoptimierung) eingesetzt.
• - Der dynamische Betriebsmodus wurde bisher bei einigen Drosselklappen (VLVTO) durchgehend benutzt, wenn der Stack oder das Luftsystem im Stack-Bypassmodus in Betrieb ist. Erfindungsgemäß wird dieser Modus aber in bestimmten Voll-Last bzw. Hochlastpunkten abgeschaltet.

A trade-off arises between the dynamic operating mode and the tight-closing operating mode of the at least one throttle valve, in which a decision must be made between the advantages with regard to the dynamics of the control of the at least one throttle valve and the advantages with regard to the efficiency of the system and the design of system components.

• - The tight-closing operating mode has previously been used (according to the state of the art) for example with some throttle valves for the operating states start-stop, start, stop, bleed-down, idle phases, etc. of the stack, in which the respective stack is not supposed to actively supply electrical power. According to the invention, the tight-closing mode is now also used to achieve the described goals (consumption, energy optimization).
• - The dynamic operating mode has previously been used continuously on some throttle valves (VLVTO) when the stack or the air system is operating in stack bypass mode. According to the invention, however, this mode is switched off at certain full load or high load points.

• Im dynamischen Betriebsmodus haben die Drosselklappen selbst in geschlossener Position eine relativ hohe Leckage. Dies führt oft zu:
  • - Effizienzverlust, schlechterer Systemwirkungsgrad, höherer H2-Verbrauch,
  • - vergrößertem Design / Auslegung und somit höheren Systemkosten, da Luft mit elektrischer Leistung verdichtet wird, die größtenteils nutzlos oder nahezu nutzlos über die Drosselklappen „verloren“ geht.

The conflict of objectives or trade-off can also be described as follows:

• In dynamic operating mode, the throttle valves have a relatively high leakage even in the closed position. This often leads to:
  • - Efficiency loss, poorer system efficiency, higher H2 consumption,
  • - enlarged design/configuration and thus higher system costs, since air is compressed using electrical power, which is largely "lost" uselessly or almost uselessly via the throttle valves.

This is particularly significant at high load points and full load points, both for operation and system design.

If you use the tight-closing operating mode instead of the dynamic operating mode for these load points, you do not have the disadvantages mentioned above, since the throttle valves are now almost completely sealed.

However, this results in a loss of dynamics, as the throttle valves must be moved relatively slowly into the sealing seat in the tight-closing operating mode (in order to protect the seal and this state can only be exited slowly.

In addition, the throttle valve loses all or part of its degrees of freedom in the tight-closing operating mode.

However, these disadvantages can be efficiently compensated for, for example, when switching between the dynamic operating mode and the tight-closing operating mode and during the tight-closing operating mode of the at least one throttle valve, different, in particular higher-level and/or lower-level, degrees of freedom, preferably at different system levels, are actively employed or used in order to compensate in particular for reduced dynamics of the at least one cathode system and/or the reduced power output of the stack connected thereto and/or reduced degrees of freedom in a control.

Advantageously, the tightly closed operating mode of the throttle valves can be used for full-load operating points and high-load operating points of the system, in particular to increase the efficiency and/or effectiveness of the system and/or to reduce consumption, in particular H2 consumption. A controller switchover can be provided for this purpose. When the controller is switched over and/or in the tightly closed operating mode, the tightly closed throttle valves can no longer actively participate in the control (but can be set as a so-called constraint or a boundary condition for the control).

During controller switching and/or in the tight-closing operating mode of the throttle valves, the higher system levels or other systems can be used in an advantageous manner to compensate for the reduced dynamics and/or reduced degrees of freedom.

• - eine Anpassung/Adaption der Leistungsverzweigung zwischen Energiewandlern (bspw. Stacks) und/oder Energiespeicher (bspw. HV-Batterie),
• - eine Anpassung/Adaption der Leistungsverzweigung zwischen den mehreren Energiewandlern insbesondere mehreren Stacks untereinander,
• - eine Anpassung/Adaption der Betriebsführung auf Ebene in einem Wassermanagement, einer Kühlsystemregelung und/oder einem Thermomanagement der Stacks.

Advantageously, at least one measure can be provided for compensation:

• - an adjustment/adaptation of the power distribution between energy converters (e.g. stacks) and/or energy storage (e.g. HV battery),
• - an adjustment/adaptation of the power distribution between the several energy converters, in particular several stacks among each other,
• - an adjustment/adaptation of the operational management at the level of water management, cooling system control and/or thermal management of the stacks.

In this way, during and after switching the throttle valves to the tight-closing operating mode, the reduced dynamics in the operation of the cathode system and/or the reduced power output of the associated stack and/or the restricted degrees of freedom in the control of the cathode system can be compensated and thus the conflict of objectives, dynamics vs. efficiency/design, can be resolved.

Advantageously, the method can be supported by prediction, which can provide trajectory planning and/or load point distribution.

• - Erhöhung der Systemeffizienz,
• - Erhöhung des Systemwirkungsgrads,
• - Absenkung des H2-Verbrauches,
• - Reduzierung von Kosten durch Verbesserung Design bzw. Verkleinerung der Auslegung von Systemkomponenten,
• - Verbesserung TCO,
• - Vermeidung Dynamik-Nachteile,
• - Vermeidung Regelungs-Nachteile, usw.

Overall, several significant advantages can be achieved using the procedure:

• - Increasing system efficiency,
• - Increasing system efficiency,
• - Reduction of H2 consumption,
• - Reduction of costs by improving design or reducing the size of system components,
• - Improve TCO,
• - Avoiding dynamic disadvantages,
• - Avoiding regulatory disadvantages, etc.

Furthermore, it can be provided that at full load and/or high load operating points in the operation of the at least one fuel cell stack, switching takes place between the dynamic operating mode and the tightly closing operating mode of the at least one throttle valve. In this way, leaks in the throttle valves in the closed position can be avoided. In this way, efficiency losses can be avoided, and the system efficiency and H2 consumption can be optimized. These advantages can be achieved in particular without disadvantages due to larger design/configuration of system components and without disadvantages due to higher system costs, since air is compressed with electrical power, which can be used largely or almost entirely to operate the stacks. This can bring significant advantages, especially at high load points and full load points.

Furthermore, it can be provided that a controller (for example in the form of a control unit of the fuel cell system) switches between the dynamic operating mode and the tight-closing operating mode of the at least one throttle valve, wherein in particular in the tight-closing operating mode the at least one throttle valve is controlled by a controller is taken and/or set as a boundary condition. In this way, the procedure can be carried out by the system's own controller.

Furthermore, it can be provided that when switching between the dynamic operating mode and the tightly closing operating mode of the at least one throttle valve and/or in the tightly closing operating mode of the at least one throttle valve, different, in particular higher-level and/or lower-level, degrees of freedom, preferably at different system levels, are actively used/used in order to compensate in particular for reduced dynamics of the at least one cathode system and/or the reduced power output of the associated stack and/or reduced degrees of freedom in a control. In this way, the reduced dynamics in the operation of the cathode system and/or the reduced power output of the associated stack and/or the restricted degrees of freedom in the control of the cathode system can be compensated for, so that the goals in terms of dynamics and efficiency can be achieved at the same time.

• - Leistungsverzweigung zwischen mindestens einem Energiespeicher und dem Brennstoffzellensystem als Ganzes,
• - Leistungsverzweigung zwischen mehreren Brennstoffzellenstapeln des Brennstoffzellensystems, und
• - Betriebsführung, insbesondere auf Ebene von einem Wassermanagement, einer Kühlsystemsteuerung und/oder einem Thermomanagement, innerhalb des mindestens einen Brennstoffzellenstapels.

Advantageously, the degrees of freedom, in particular higher-level and/or lower-level degrees of freedom, can have the following levels, preferably on different system levels:

• - Power split between at least one energy storage device and the fuel cell system as a whole,
• - Power splitting between several fuel cell stacks of the fuel cell system, and
• - Operational management, in particular at the level of water management, cooling system control and/or thermal management, within the at least one fuel cell stack.

In addition, it can be provided that the at least one throttle valve switches from the dynamic operating mode to the tightly closing operating mode when a load point in the operation of the at least one fuel cell stack exceeds a certain, in particular first, threshold value, possibly after a period of time has elapsed.

In addition, it can be provided that the at least one throttle valve switches from the tightly closing operating mode to the dynamic operating mode when a load point falls below a certain, in particular second, threshold value during operation of the at least one fuel cell stack, if necessary after a period of time has elapsed

In this way, automatic switching can be carried out, e.g. by means of a controller.

It is also conceivable that a consumption parameter and/or a tank level are used as trigger parameters with specific threshold values to switch between the dynamic operating mode and the tightly closing operating mode of the at least one throttle valve. In this way, different mechanisms can be provided to carry out an automatic switchover.

Advantageously, the method can be carried out in advance. In this way, trajectory planning and/or load distribution can be taken into account in order to carry out an automatic switchover in a targeted and efficient manner.

The method can advantageously be carried out in a fuel cell system with several fuel cell stacks. In this way, different, in particular higher-level and/or lower-level, degrees of freedom can be actively used, preferably at different system levels, in order to compensate in particular for reduced dynamics of the at least one cathode system and/or the reduced power output of the stack connected to it and/or reduced degrees of freedom in a control system.

The invention further provides: a computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to carry out a method which can run as described above. The same advantages as described above in connection with the method according to the invention can be achieved with the aid of the computer program product according to the invention. These advantages are fully incorporated herein by reference.

The invention further provides: a control unit, having a computing unit and a memory unit in which a code is stored which, when at least partially executed by the computing unit, carries out a method which can run as described above. With the help of the control unit according to the invention, the same advantages can be achieved that were described above in connection with the method according to the invention. These advantages are fully referred to here.

The invention further provides: a fuel cell system, having a corresponding control unit, which is designed to carry out a method which can take place as described above. With the aid of the fuel cell system according to the invention, the same advantages can be achieved that were described above in connection with the method according to the invention. These advantages are fully referred to here.

Preferred embodiments:

• 1 eine schematische Darstellung eines Zielkonflikts zwischen der Dynamik vs. Effizienz und Auslegung/Design,
• 2 einen beispielhaften Ablauf eines Verfahrens im Rahmen der vorliegenden Offenbarung, und
• 3 eine schematische Darstellung eines Brennstoffzellensystems.

The invention and its further developments as well as its advantages are explained in more detail below using drawings. They show schematically:

• 1 a schematic representation of a conflict of objectives between dynamics vs. efficiency and design,
• 2 an exemplary sequence of a method within the scope of the present disclosure, and
• 3 a schematic representation of a fuel cell system.

The 1 to 3 serve to explain a method which has been developed for operating a fuel cell system 100 (in short as system 100). The system 100 can have at least one or more fuel cell stacks 101 (in short stack or stacks) and at least one (e.g. one for each stack or a common one for some stacks 101) cathode system 10. An exemplary fuel cell system 100 is shown in the 3 shown.

The at least one cathode system 10 can have a plurality of valves and/or throttle valves VIV. Among these, at least one or more throttle valves VLVTO with a control function and/or a shut-off function, preferably with a sealing effect, can be present.

When a VLVTO throttle valve is used in control mode, it can be closed or nearly closed, but will have significant leakage in this state.

If a throttle valve VLVTO is set in sealing mode, it cannot be regulated quickly, but must first be slowly moved out of sealing mode.

If the at least one throttle valve VLVTO has a conflict of objectives between dynamics and tightness when controlling the at least one throttle valve VLVTO, it is now proposed that during operation of the at least one fuel cell stack 10, switching is carried out between the dynamic operating mode opR and the tight-closing operating mode opD of the at least one throttle valve VLVTO in order to optimize in particular an efficiency, a degree of effectiveness and/or a consumption of the fuel cell system 100.

The fuel cell system 100 can advantageously have a plurality of fuel cell stacks 101, so-called fuel cell stacks or, in short, stacks, each with a plurality of stacked repeat units in the form of fuel cells, for example PEM fuel cells.

The fuel cell system 100 can advantageously be used for mobile applications, such as in motor vehicles, in particular commercial vehicles, or for stationary applications, such as in generator systems.

The fuel cell system 100 can advantageously have a control unit 200, which can be designed for controlling the cathode system 10, in particular for controlling a compression unit of the cathode system 10 and preferably for controlling the valves and/or throttle valves, preferably for controlling the at least one throttle valve VLVTO with a control function and/or a shut-off function, preferably with a sealing effect, according to the method according to the invention.

The cathode system 10 can also be referred to as an air system.

The compression unit can also be referred to as a compression system. The compression unit can have at least one or more compressors Comp. At least one compressor Comp can be driven electrically, for example using an electric motor. At least one compressor Comp can be driven fluidically, preferably using a turbine Turb or a turbocharger. At least one compressor Comp can also be designed as single-stage, two-stage or double-flow. The compression unit can also have at least one turbine Turb to support at least one compressor Comp.

1. 1. eine Drosselklappe ByTurb in einem Bypass einer Turbine im Abgaspfad eines Brennstoffzellensystems,
2. 2. eine Drosselklappe ByCath in einem Bypass eines Stack-Kathodenpfades,
3. 3. eine Drosselklappe ByEGR in einem AGR/EGR -Pfad (Abgasrückführung / eng. „exhaust gas recirculation“),
4. 4. eine Drosselklappe stromaufwärts eines Kathoden-Einlasses des jeweiligen Stacks, d. h. in einem (Haupt-)Kathodenpfad,
5. 5. eine Drosselklappe stromabwärts eines Kathoden-Auslasses des jeweiligen Stacks, d. h. im (Haupt-)Kathodenpfad,
6. 6. eine Drosselklappe ByComp in einem Bypass zu einem Verdichter
7. 7. eine Drosselklappe ByEGT in einem Abgastransferpfad (EGT=„exhaust gas transfer“), durch die ein Teil des Abgases eines Stacks in den Zuluftpfad eines anderen Stacks geleitet werden kann
8. 8. eine Drosselklappe ByHumid in einem Bypass eines Befeuchters
9. 9. eine Drosselklappe an weiteren/anderen Stellen eingesetzt werden, usw.

The at least one throttle valve VLVTO within the scope of the invention can preferably have both a control function and a shut-off function with a sealing effect. Such throttle valves can, for example:

1. 1. a throttle valve ByTurb in a bypass of a turbine in the exhaust path of a fuel cell system,
2. 2. a throttle valve ByCath in a bypass of a stack cathode path,
3. 3. a throttle valve ByEGR in an EGR/EGR path (exhaust gas recirculation),
4. 4. a throttle valve upstream of a cathode inlet of the respective stack, ie in a (main) cathode path,
5. 5. a throttle valve downstream of a cathode outlet of the respective stack, ie in the (main) cathode path,
6. 6. a throttle valve ByComp in a bypass to a compressor
7. 7. a throttle valve ByEGT in an exhaust gas transfer path (EGT), through which part of the exhaust gas from one stack can be directed into the intake air path of another stack
8. 8. a ByHumid throttle valve in a bypass of a humidifier
9. 9. a throttle valve can be used in other/different locations, etc.

The method particularly addresses the VLVTO throttle valves where leaks lead to loss of efficiency in the system 100, such as throttle valves 1, 2, 3, 6 and 7.

• - Der dichtschließende Betriebsmodus opD wurde bisher (nach Stand der Technik) bspw. bei manchen Drosselklappen für die Betriebszustände Start-Stopp, Start, Stopp, Bleed-down Stillstandsphasen usw. des Stacks eingesetzt werden, bei denen der jeweilige Stack nicht aktiv elektrische Leistung liefern soll. Erfindungsgemäß wird der dichtschließende Betriebsmodus opD nun aber auch zur Erreichung der beschriebenen Ziele (Verbrauch, Energieoptimierung) eingesetzt.
• - Der dynamische Betriebsmodus opR wurde bisher bei einigen Drosselklappen (VLVTO) durchgehend benutzt, wenn der Stack oder das Luftsystem im Stack-Bypassmodus in Betrieb ist. Erfindungsgemäß wird dieser Modus aber in bestimmten Voll-Last bzw. Hochlastpunkten abgeschaltet.

As the 1 As suggested, a conflict of objectives (so-called trade-off) arises between the dynamic operating mode opR and the tightly closing operating mode opD of the at least one throttle valve VLVTO, in which a decision must be made between the advantages with regard to the dynamics in the control of the at least one throttle valve VLVTO and the advantages with regard to the efficiency of the fuel cell system 100 and the design of system components, in particular the compressor Comp.

• - The tight-closing operating mode opD has previously been used (according to the state of the art) for example with some throttle valves for the operating states start-stop, start, stop, bleed-down, idle phases, etc. of the stack, in which the respective stack is not supposed to actively supply electrical power. According to the invention, the tight-closing operating mode opD is now also used to achieve the described goals (consumption, energy optimization).
• - The dynamic operating mode opR has previously been used continuously on some throttle valves (VLVTO) when the stack or the air system is operating in stack bypass mode. According to the invention, however, this mode is switched off at certain full load or high load points.

• Im dynamischen Betriebsmodus opR haben die Drosselklappen VLVTO selbst in geschlossener Position eine relativ hohe Leckage. Dies führt zumeist zu:
  • - Effizienzverlust, schlechterer Systemwirkungsgrad, höherer H2-Verbrauch,
  • - vergrößertem Design / Auslegung und somit höheren Systemkosten, da Luft mit elektrischer Leistung verdichtet wird, die größtenteils nutzlos oder nahezu nutzlos über die Drosselklappen VLVTO „verloren“ geht.

The conflict of objectives or trade-off can also be described as follows:

• In the dynamic operating mode opR, the throttle valves VLVTO have a relatively high leakage even in the closed position. This usually leads to:
  • - Efficiency loss, poorer system efficiency, higher H2 consumption,
  • - enlarged design and thus higher system costs, since air is compressed using electrical power, which is mostly uselessly or almost uselessly "lost" via the throttle valves VLVTO.

This is particularly significant at high load points and full load points in the operation of the stack and/or the overall system.

If the tight-closing operating mode opD is used for these load points instead of the dynamic operating mode opR, the disadvantages mentioned above are not present, since the throttle valves VLVTO are now almost completely tightly closed.

However, this results in a loss of dynamics, since the throttle valves VLVTO must be moved relatively slowly into the sealing seat in the tight-closing operating mode opD and this state can only be left slowly in order to protect the seal.

In addition, the throttle valve VLVTO loses in the tight-closing operating mode opD or a part thereof for the degrees of freedom in the control of the cathode system 10.

These disadvantages can be efficiently compensated in an advantageous manner if, when switching between the dynamic operating mode opR and the tightly closing operating mode opD of the at least one throttle valve VLVTO and/or in the tightly closing operating mode opD of the at least one throttle valve VLVTO, different, in particular higher-level and/or lower-level, degrees of freedom Top1Ctl, Top2Ctl, Top3Ctl, preferably on different system levels 1, 2, 3, are actively used/used in order to compensate in particular for reduced dynamics of the at least one cathode system 10 and/or the reduced power output of the associated stack and/or reduced degrees of freedom in a control.

• - Leistungsverzweigung zwischen mindestens einem Energiespeicher und dem Brennstoffzellensystem 100 als Ganzes,
• - Leistungsverzweigung zwischen mehreren Brennstoffzellenstapeln 101 des Brennstoffzellensystems 100, und
• - Betriebsführung, insbesondere auf Ebene von einem Wassermanagement, einer Kühlsystemsteuerung und/oder einem Thermomanagement, innerhalb des mindestens einen Brennstoffzellenstapels 101.

Advantageously, the, in particular higher-level and/or lower-level free levels Top1Ctl, Top2Ctl, Top3Ctl, preferably on different system levels 1, 2, 3, have the following levels:

• - power split between at least one energy storage device and the fuel cell system 100 as a whole,
• - power splitting between several fuel cell stacks 101 of the fuel cell system 100, and
• - Operational management, in particular at the level of water management, cooling system control and/or thermal management, within the at least one fuel cell stack 101.

It is advantageously proposed that the tightly closed operating mode opD of the throttle valves VLVTO be used for full-load operating points and high-load operating points of the system, in particular to increase the efficiency and/or effectiveness of the system 100 and/or to reduce consumption, in particular H2 consumption. A controller switchover can be provided for this purpose. During the controller switchover and/or in the tightly closed operating mode, the tightly closed throttle valves can no longer actively participate in the control, but can be set as a boundary condition for the control.

During controller switching and/or in the tight-closing operating mode opD of the throttle valves VLVTO, the higher-level system levels or other systems can be used in an advantageous manner to compensate for the reduced dynamics and/or reduced degrees of freedom.

• - eine Anpassung/Adaption der Leistungsverzweigung zwischen Energiewandlern bspw. Stacks und/oder Energiespeicher bspw. HV-Batterie,
• - eine Anpassung/Adaption der Leistungsverzweigung zwischen den mehreren Energiewandlern insbesondere mehreren Stacks untereinander,
• - eine Anpassung/Adaption der Betriebsführung auf Ebene in einem Wassermanagement, einer Kühlsystemregelung und/oder einem Thermomanagement der Stacks.

Advantageously, at least one measure can be provided for compensation:

• - an adjustment/adaptation of the power distribution between energy converters, e.g. stacks and/or energy storage, e.g. HV battery,
• - an adjustment/adaptation of the power distribution between the several energy converters, in particular several stacks among each other,
• - an adjustment/adaptation of the operational management at the level of water management, cooling system control and/or thermal management of the stacks.

In this way, when switching the throttle valves VLVTO to the tight-closing operating mode opD and/or in the tight-closing operating mode opD of the throttle valves VLVTO, the reduced dynamics in the operation of the cathode system 10 and/or the reduced power output of the associated stack and/or the restricted degrees of freedom in the control of the cathode system 10 can be compensated and thus the conflict of objectives between dynamics vs. efficiency/design/consumption can be resolved.

Advantageously, the method can be supported by prediction, which can provide trajectory planning and/or load point distribution.

• - Erhöhung der Systemeffizienz,
• - Erhöhung des Systemwirkungsgrads,
• - Absenkung des H2-Verbrauches,
• - Reduzierung von Kosten durch Verbesserung Design bzw. Verkleinerung der Auslegung von Systemkomponenten,
• - Verbesserung TCO,
• - Vermeidung Dynamik-Nachteile,
• - Vermeidung Regelungs-Nachteile, usw.

Overall, several significant advantages can be achieved using the procedure:

• - Increasing system efficiency,
• - Increasing system efficiency,
• - Reduction of H2 consumption,
• - Reduction of costs by improving design or reducing the size of system components,
• - Improve TCO,
• - Avoiding dynamic disadvantages,
• - Avoiding regulatory disadvantages, etc.

The 2 : shows an exemplary procedure for solving the described conflict of objectives.

On the left (first column) the modes opR, opD of the relevant/addressed throttle valves VlvTO are shown.

The third column shows the control modes A and B of the cathode system 10.

A: All VLV throttle valves (VLVNE and VLVTO) can be used directly to control the cathode system 10.

B: The throttle valves VLVTO in the tight-closing operating mode opD can no longer be used directly to control the cathode system 10. They can be taken into account as boundary conditions (throttle valve VLVTO = tightly closed). If there are several throttle valves VLVTO in the cathode system 10 that have such a conflict of objectives, then only a subset jred < j of the throttle valves can be moved to the tight-closing operating mode opD.

In the cathode system 10, during the switching/transitions T1, T2 and in the tight-closing operating mode opD of the tightly closed throttle valves VLVTO, there is a reduced Dynamics. In addition, the cathode system 10 has fewer degrees of freedom in the tightly closed operating mode opD of the tightly closed throttle valves VLVTO.

As the 2 on the right-hand side, the reduced dynamics and/or reduced degrees of freedom can be compensated by means of the cross-system control, advantageously by different, in particular higher-level and/or lower-level, degrees of freedom Top1Ctl, Top2Ctl, Top3Ctl, preferably on different system levels 1, 2, 3.

• Leistungsverzweigung der Gesamtleistung zwischen einem Energiespeicher (z.B. einer Hochvolt-Batterie) und den Stacks.

First system level 1 or degree of freedom Top1Ctl can provide:

• Power distribution of the total power between an energy storage device (e.g. a high-voltage battery) and the stacks.

If the stacks do not deliver enough power P due to slow dynamics and/or limited degrees of freedom, a battery can “boost” the power, so to speak.

If the stacks deliver too much power P due to slowed dynamics and/or restricted degrees of freedom, a battery can absorb excess power.

• Leistungsverzweigung zwischen den einzelnen Stacks.

Second system level 2 or degree of freedom Top2Ctl can provide:

• Power distribution between the individual stacks.

This implementation can be carried out topology-dependently.

Preferably, stacks whose air system is not slowed down can be used to compensate for the slowed dynamics of the stacks whose air system is slowed down.

• Wassermanagement, ggf. kombiniert mit Kühlsystemsteuerung und/oder Thermomanagement.
• Für jeden Stack i=1,2,3,4, etc. gibt es individuelle Betriebsbedingungen mit Freiheitsgraden. Diese Freiheitsgrade beziehen sich insbesondere auf das Wassermanagement, bei dem u.a. Druck, Lambda (Luftüberschuß) und Stacktemperatur als wichtige Größen aufeinander abzustimmen sind.

Third system level 3 or degree of freedom Top3Ctl can provide:

• Water management, if necessary combined with cooling system control and/or thermal management.
• For each stack i=1,2,3,4, etc. there are individual operating conditions with degrees of freedom. These degrees of freedom relate in particular to water management, where pressure, lambda (excess air) and stack temperature are important variables that must be coordinated with one another.

The degrees of freedom within this system level 3 can be used to compensate for the slowed dynamics and the restricted degrees of freedom of the air system.

For example, the degree of freedom “cathode pressure in the stack vs. lambda cathode path stack” can be used here.

Since the moisture content of the membrane is not so dynamic in some ways, a temporary deviation between the target and actual values of the water management can be tolerated.

Advantageously, a prediction PR can be carried out before a switchover, cf. a star-shaped cloud in the 2 In this case, consideration/adjustment can be made in advance, even before switching, on the other system levels 1, 2, 3, e.g. checking whether the battery SOC is sufficient for support (Top1Ctl), and/or whether the other stacks (Top2Ctl) are in a condition to possibly support the dynamics, and/or whether the operating conditions of stacks (Top3Ctl) can be adjusted so that the air system can act more slowly or with less restrictions (e.g. membrane condition in a good middle range, so that temporary deviations to "slightly" wetter or "slightly" drier have no negative effects).

In the second column of the 2 the time sequence and the triggers for switching between are shown.

Even during the switching from opR to opD and back from opD to opR, slower dynamics are present in the air system and can be compensated by different system levels 1, 2, 3.

If the load point P increases during operation of the system 100 and exceeds a first threshold S1, then the switchover can be prepared and triggered. The exceedance can also be debounced in time, i.e. the trigger is only set after a certain period of time dt.

If the load point P falls below a second threshold S2 in switched operation (with slower dynamics opD), the switchover back is prepared and then triggered. This can also be debounced in time, i.e. the trigger is only set after a certain period of time dt.

Alternatively or in addition to the electrical load P, other or additional variables can also be used for triggering, e.g. a consumption parameter (e.g. Eco mode vs. Sport mode and/or the tank content, e.g. with a lower certain threshold, and/or the H2 costs, e.g. with a certain upper threshold, etc.)

For all triggers, a prediction PR can advantageously be performed.

In the CV commercial vehicle sector, especially for long-haul trucks, the prediction PR of the driving trajectory can be taken into account in an optimization-based manner.

Through the prediction PR, the switching from opR to opD and back from opD to opR and the preparations on different system levels 1, 2, 3 can be carried out in a targeted manner.

Optimization in terms of consumption/system efficiency can advantageously be implemented without any loss of dynamics.

A corresponding control unit 200 for carrying out the method also represents an aspect of the invention.

A corresponding fuel cell system 100 with a corresponding control unit 200 for carrying out the method also represents an aspect of the invention.

3 shows an exemplary fuel cell system 100 with two fuel cell stacks 101 and one cathode system 10 each.

The throttle valves VLVTO that the process addresses are outlined with dotted lines. These throttle valves VLVTO are relevant for system efficiency and have a conflicting objective in the sense of the present idea. If large leaks are avoided here (as is usually the case with throttle valves in non-tight-closing operation), significant fuel savings can be achieved.

Shown in 3 is an example of a system 100 with 2 stacks and EAC-TAC cathode systems 10, which are used, for example, for high-performance systems 100 (high system pressure).

• Systemsteuerung (bspw. durch Steuereinheit 200) des Kathodensystems 10 = f(EAC, VLVNE, ByTurb, ByCath, ByEGR).

The throttle valves VLVTO in the dynamic operating mode opR can provide the following degrees of freedom for the control or the control unit 200:

• System control (e.g. by control unit 200) of the cathode system 10 = f(EAC, VLVNE, ByTurb, ByCath, ByEGR).

• Systemsteuerung 200 (10) = f(EACT, VlvNe)
• oder (nur eine Teilmenge von VLVTO)
• Systemsteuerung (bspw. durch Steuereinheit 200) des Kathodensystems 10 = f(EACT, VlvNe, ByCath).

The throttle valves VLVTO in the tight-closing operating mode opD can provide the following degrees of freedom for the control or the control unit 200:

• Control Panel 200 (10) = f(EACT, VlvNe)
• or (only a subset of VLVTO)
• System control (e.g. by control unit 200) of the cathode system 10 = f(EACT, VlvNe, ByCath).

The above description of the figures describes the present invention exclusively in the context of examples. Of course, individual features of the embodiments can be freely combined with one another, provided it is technically expedient, without departing from the scope of the invention.

Claims (11)

Method for operating a fuel cell system (100) with at least one fuel cell stack (101) and at least one cathode system (10), wherein the at least one cathode system (10) has a plurality of valves and/or throttle valves (VIV), comprising at least one throttle valve (VLVTO) with a control function and/or a shut-off function, preferably with a sealing effect, characterized in that, if the at least one throttle valve (VLVTO) has a conflict of objectives between dynamics and tightness when controlling the at least one throttle valve (VLVTO), the operation of the at least one fuel cell stack (10) is switched between the dynamic operating mode (opR) and the tight-closing operating mode (opD) of the at least one throttle valve (VLVTO), in order in particular to optimize an efficiency, a degree of effectiveness and/or a consumption of the fuel cell system (100). procedure according to claim 1 , characterized in that at full-load and/or high-load operating points in the operation of the at least one fuel cell stack (10) there is a switch between the dynamic operating mode (opR) and the tight-closing operating mode (opD) of the at least one throttle valve (VLVTO). procedure according to claim 1 or 2 , characterized in that a controller switches between the dynamic operating mode (opR) and the tight-closing operating mode (opD) of the at least one throttle valve (VLVTO), wherein in particular in the tight-closing operating mode (opD) the at least one throttle valve (VLVTO) is excluded from control and/or is set as a boundary condition. Method according to one of the preceding claims, characterized in that when switching between the dynamic operating mode (opR) and the tightly closing operating mode (opD) of the at least one throttle valve (VLVTO) and/or in the tightly closing operating mode (opD) of the at least one throttle valve (VLVTO), different, in particular higher-level and/or lower-level, degrees of freedom (Top1Ctl, Top2Ctl, Top3Ctl), preferably on different system levels (1, 2, 3), are used and/or utilized, in particular actively, in order to compensate in particular for reduced dynamics of the at least one cathode system (10) and/or reduced power output of the stack associated with it and/or reduced degrees of freedom in a control. Method according to the preceding claim, characterized in that the, in particular higher-level and/or lower-level degrees of freedom (Top1Ctl, Top2Ctl, Top3Ctl), preferably on different system levels (1, 2, 3), have the following levels: - power branching between at least one energy storage device and the fuel cell system (100) as a whole, - power branching between several fuel cell stacks (101) of the fuel cell system (100), and - operational management, in particular at the level of a water management system, a cooling system control system and/or a thermal management system, within the at least one fuel cell stack (101). Method according to one of the preceding claims, characterized in that the at least one throttle valve (VLVTO) is switched from the dynamic operating mode (opR) to the tightly closing operating mode (opD) when, during operation of the at least one fuel cell stack (10), a load point exceeds a specific, in particular first, threshold value (SW1), if necessary after a period of time (dt) has elapsed, and/or the at least one throttle valve (VLVTO) is switched from the tightly closing operating mode (opD) to the dynamic operating mode (opR) when, during operation of the at least one fuel cell stack (10), a load point falls below a specific, in particular second, threshold value (SW2), if necessary after a period of time (dt) has elapsed. Method according to one of the preceding claims, characterized in that a consumption parameter and/or a tank level are used as trigger parameters with certain threshold values for switching between the dynamic operating mode (opR) and the tight-closing operating mode (opD) of the at least one throttle valve (VLVTO). Method according to one of the preceding claims, characterized in that the method is carried out in advance and/or that the method is carried out in a fuel cell system (100) with a plurality of fuel cell stacks (101). Computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to carry out a method according to one of the preceding claims. Control unit (200) comprising a computing unit and a memory unit in which a code is stored which, when at least partially executed by the computing unit, implements a method according to one of the preceding Claims 1 until 8 carries out. Fuel cell system (100) comprising a control unit (200) according to the preceding claim.

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