Method and system for operating a fuel cell system

Abstract

The invention relates to a method and to a system for operating a fuel cell system (22) and at least one sub-system (30) of the fuel cell system (22). According to the invention, these are arranged in a vehicle (10), wherein the energy for a drive train (12) of the vehicle (10) can be drawn both from the fuel cell system (22) and from an alternative energy store (26). The method comprises the following method steps: first, the number and duration of shut-down and/or stop phases of the vehicles (10) in a defined time interval in a first vehicle state (86) or in a second vehicle state (88) is determined based on vehicle state-specific learning functions (90, 112). Operating parameters of the fuel cell system (22) and of the at least one sub-system (30) of the fuel cell system (22) are then adjusted in dependence on the determined number and duration of shut-down and/or stop phases of the vehicle (10).

Claims

1. A method for operating a fuel cell system (22) and at least one subsystem (30) of the fuel cell system (22), which are arranged in a vehicle (10), wherein energy for a drive train (12) of the vehicle (10) can be taken from both the fuel cell system (22) as well as from an alternative energy store (26), the method comprising: a) determining a number and duration of shutdown and/or stop phases of the vehicle (10) in a defined time interval in a first vehicle state (86) or in a second vehicle state (88) based on vehicle state-specific learning functions (90, 112); b) setting operating parameters of the fuel cell system (22) and of the at least one subsystem (30) of the fuel cell system (22) in dependence on the number and duration of shutdown and/or stop phases of the vehicle (10); and c) responsive to determining the number of shutdown phases exceeds a first threshold value within the defined time interval and an average duration of the shutdown phases exceeds a second threshold value, setting a first and second operating state of the fuel cell system (22).

2. The method as claimed in claim 1, wherein, in addition to the method steps a) and b) an adaptation (96) of a state-of-charge range (SOC) of the alternative energy store (26) is performed.

3. The method as claimed in claim 2, wherein the adaptation of the state-of-charge range of the alternative energy store (26) comprises an adaptation of a min-max limit and/or and adaptation of a control/regulation of the state of charge.

4. The method as claimed in claim 1, wherein in the first learning function (90) associated with the first vehicle state (86), the operating mode of the vehicle 10 with regard to the shutoff and/or stop phases of the vehicle (10) between individual journeys up until restarting is carried out, for the sake of which, internal timers on control devices (80), an integrated network data exchange (92), a data storage on a local EEPROM as well as an evaluation of the operating mode in hours and/or days and/or longer time periods are carried out.

5. The method as claimed in claim 1, wherein, in a second learning function (112) associated with the second vehicle state (88), the operating mode of the vehicle (10) is determined during at least one driving cycle in the case of a vehicle (10) that is not shut down with regard to occurring start/stop phases.

6. The method as claimed in claim 1, wherein the first learning function (90) and/or the second learning function (112) take a current driving route of the vehicle (10) into account.

7. The method as claimed in claim 1, wherein the first learning function (90) and/or the second learning function (112) take into account the ambient temperature and at least one other operating parameter selected from the group consisting of current consumer devices within the on-board network, humidity of the ambient air, aging process of the battery, aging process of the fuel cell stack (50), and condition of the vehicle air-conditioning.

8. The method as claimed in claim 1, wherein the first operating state of the fuel cell system (22) comprises a delayed shutdown of the fuel cell system (22), within which the fuel cell system (22) is operated in idling mode and resulting energy is stored in the alternative energy store (26) and/or transferred to additional consumer devices (110).

9. The method as claimed in claim 1, wherein, when the determined number of stop phases exceeds a third threshold value within the defined time interval and an average duration of the stop phases exceeds a fourth threshold value, a second or a third operating state of the fuel cell system (22) is set.

10. The method as claimed in claim 1, wherein the second operating state of the fuel cell system (22) entails operating the air conveyance subsystem (30) of the fuel cell system (22) at a minimum load and a minimum rotational speed.

11. The method as claimed in claim 9, wherein the second operating state of the fuel cell system (22) comprises conducting of an air-mass flow by means of an open bypass valve (32) past the fuel cell stack (50) of the fuel cell system (22).

12. The method as claimed in claim 9, wherein, in a third operating state of the fuel cell system (22), switching on additional consumer devices (110) takes place for the case that the SOC of the alternative energy store (26) has reached its maximum.

13. A non-transitory computer-readable medium for operating a fuel cell system (22) and at least one subsystem (30) of the fuel cell system (22), which are arranged in a vehicle (10), wherein energy for a drive train (12) of the vehicle (10) can be taken from both the fuel cell system (22) as well as from an alternative energy store (26), the computer-readable medium containing computer-executable instructions that when executed by a computer device cause the computer device to: determine a number and duration of shutdown and/or stop phases of the vehicle (10) in a defined time interval in a first vehicle state (86) or in a second vehicle state (88) based on vehicle state-specific learning functions (90, 112); set operating parameters of the fuel cell system (22) and of the at least one subsystem (30) of the fuel cell system (22) in dependence on the determined number and duration of shutdown and/or stop phases of the vehicle (10); and responsive to determining the number of shutdown phases exceeds a first threshold value within the defined time interval and an average duration of the shutdown phases exceeds a second threshold value, set a first and second operating state of the fuel cell system (22).

14. A system for operating a fuel cell system (22), which is arranged in a vehicle (1), wherein energy for a drive train (12) of the vehicle (10) can be taken from the fuel cell system (22) or from an alternative energy store (26), wherein this comprises a first module (82) for carrying out a first learning function (90) and a second module (84) for carrying out a second learning function (112), in which the operating mode of the vehicle (10) is determined with regard to shutdown/break times between individual journeys up until restarting or the operating mode of the vehicle (10) during a driving cycle with regard to occurring start/stop phases, wherein the fuel cell system (22) comprises: a fuel cell stack (50) and at least one air conveyance subsystem (30), where a pressure control valve (34) for air conveyance at a pressure subjected to minimum load and a bypass valve (32) are completely open in order to lead an air-mass flow occurring at minimum load of the air conveyance subsystem (30) past the fuel cell stack (50).

15. The system for operating a fuel cell system (22) as claimed in claim 14, wherein a stop valve (36) is arranged in front of the fuel cell stack (50), an opening pressure of which is over a minimum pressure, which is generated by the air conveyance subsystem (30) via a minimum air compression.

16. The system as claimed in claim 15 connected to a navigation system, via which a certain destination and a remaining distance to the destination are known.

17. A vehicle (10) with a system as claimed in claim 14, wherein the alternative energy store (26) comprises one or a plurality of traction batteries, supercapacitors, or both.

Description

BRIEF DESCRIPTION OF THE INVENTION

(1) Based on the figures, in the following, the method according to the invention and the system are described in more detail.

(2) FIG. 1 shows an exemplary illustration of vehicle with a system according to the invention and

(3) FIG. 2 shows a schematic illustration of a method in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

(4) In the illustration in accordance with FIG. 1, only one possible topology of a fuel cell system 22 is shown with at least one alternative energy store 26 as an example for explaining the method. Here, it is explicitly pointed out that, in addition to the vehicle topology shown in FIG. 1, many other design possibilities of a fuel cell system 22 can be implemented with at least one alternative energy store 26.

(5) FIG. 1 shows a vehicle 10 equipped with a fuel cell system 22 and at least one alternative energy store 26. The fuel cell system 22 and the alternative energy store 26 can make the full energy or a part of the energy available to a drive train 12 of the vehicle 10 respectively. Furthermore, the alternative energy store 26 can typically also recover energy. In addition to the drive train 12 of an axle 18, additional drive trains 12 can be installed for further axles of vehicle 10, which is not shown.

(6) The fuel cell system 22 is connected to a control device 80, wherein this is equipped with known monitoring and diagnostic functions and, in particular, also set up to connect or disconnect the fuel cell system 22 to the drive train 12 of the vehicle 10, wherein the control device 80 can also trigger and carry out the shutdown procedure of the fuel cell system 22. In the control device 80, a first module 82 for performing a first learning function 90 and another second module 84 for performing a second learning function 112 are implemented (cf. FIG. 2).

(7) The at least one alternative energy store 26, for example, a traction battery or a supercapacitor, is connected to another control device, wherein this is occupied with known monitoring and diagnostic functions and is also set up to connect or disconnect the alternative energy store 26 to the drive train 12 of the vehicle 10. The other control device can also be designed and designated as a battery management system. In principle, it is also conceivable to omit the other control device and also accommodate the control system, as well as the monitoring and diagnostic function for the at least one alternative energy store 26 within the control device 80.

(8) FIG. 1 shows that the drive train 12 of the vehicle 10 comprises a gearbox 14 with at least one electric machine 16. The electric machine 16 is the drive for the driven axle 18. An inverter 20 is associated with the at least one electric machine 16; a bidirectionality should be indicated by means of position 62, meaning the at least one electric machine 16 works both in generator as well as in motor mode. The components of the drive train 12 of the vehicle 10 are marked in FIG. 1 by a dot/dashed line.

(9) The vehicle 10 furthermore comprises the fuel cell system 22. This comprises at least one energy store 24, which is designed as an H.sub.2 tank. The fuel cell system 22 furthermore comprises an air conveyance subsystem 30. In this, there is an air filter 38 and a downstream mass-flow sensor 40. The air conveyance subsystem 30 furthermore comprises a compressor 42, which is driven by a compressor drive 44 designed as an electric drive. Furthermore, an intermediate cooler 46 is arranged in the air conveyance subsystem 30, by means of which, after the compressor 42, the heated air is cooled again before it flows to a fuel cell stack 50 after passing through the intermediate cooler 46 of the fuel cell system 22. The fuel cell stack 50 is temperature controlled for its part by a cooling circuit 52, the components of which are only schematically indicated in the illustration in accordance with FIG. 1. On the output side, the fuel cell stack 50 comprises a plus pole 54 and a minus pole 56.

(10) The inverter 20 of the drive train 12 is electrically connected to a fuel cell converter 64.

(11) From the representation in accordance with FIG. 1, it is furthermore apparent that the vehicle 10 comprises at least one alternative energy store 26. The alternative energy store 26 can be designed as at least one high-voltage battery or as an arrangement of supercapacitors. As can be recognized from the illustration in accordance with FIG. 1, the alternative energy store 26 is electrically connected to both the drive train 12 as well as to the air conveyance subsystem 30 via a high-voltage converter 60. The high-voltage converter 60 is bidirectionally operable, indicated by reference number 62.

(12) In addition, the vehicle 10 comprises a conventional 12-volt vehicle battery 28, which is connected to the drive train 12 of the vehicle 10 via a low-voltage converter 58.

(13) It must be noted that the fuel cell system 22 in the design variant shown has a bypass valve 32, via which the air supplied by the air conveyance subsystem 30 can be guided past the fuel cell stack 50. In addition, there is a pressure control valve 34 in the fuel cell system 22 on the outflow side. On the input side, the fuel cell stack 50 is connected to a stop valve 36. Since the fuel cell system 22 designed with the topology shown in FIG. 1 has a bypass valve 32, another possibility for controlling and regulating the same is available. However, this is only a design option; the method proposed according to the invention is also applicable to a fuel cell system 22, which is designed without bypass valve 32.

(14) While, in the illustration in accordance with FIG. 1, the components of the vehicle 10, in particular the components of the drive train 12, the ones of the fuel cell system 22, as well as those of the air conveyance subsystem 30, and furthermore, alternative energy stores 26 and more of the like are represented, based on the illustration of the flow chart in FIG. 2, the method proposed according to the invention for reducing the start/stop operations within the mobile fuel cell system 22 as well as of the at least one air conveyance subsystem 30 based on a vehicle “off” state (cf. position 86), as well as based on a vehicle “on” state (cf. position 88) is described in more detail.

(15) As can be seen in the flow chart in accordance with FIG. 2, the operating mode of the vehicle 10 is taken under consideration for the past journeys and, if applicable, also with regard to other destinations by means of a first learning function 90. The first leaning function 90 in the first module 82 consequently delays the shutdown of the fuel cell system 22 and the shutdown of the air conveyance subsystem 30. The first learning function 90 determines the operating mode of the vehicle 10, above all, with regard to the shutdown/breaktimes between the individual journeys for as long until a restart of the vehicle 10 takes place. The first learning function 90 uses internal timers in the control devices 80 or also an integrated network data exchange 92, via which data from outside the vehicle 10, for example, via a navigation system or via a cloud, can be transferred to the first learning function 90 and taken into consideration in the determination of the operating mode of the vehicle 10. The corresponding data can be stored locally in EEPROM's or in the case of integrated network vehicles, exteriorly, for example in a cloud. The first leaning function 90 determines if the vehicle 10 stops very frequently, for example, within the minute range and then starts again, which is a typical operating mode for delivery vehicles, taxi operations and the like. In the following, this operating mode, which is characterized by frequent, short stops is referred to as the “delivery mode” 94. The first learning function 90 can evaluate the operating mode of the vehicle 10 both in shorter time frames, for example, in hours or days, as well as over longer periods, such as weeks and months.

(16) The data ascertained within the first learning function 90 can then be used in order to adapt corresponding actions in the fuel cell system 22 and in the air conveyance subsystem 30 or in the case of additional consumer devices and in particular to adapt the state of charge (SOC) of at least one alternative energy store 26. If the vehicle 10 assumes a vehicle “on” state 88 (idling) in accordance with the illustration in FIG. 2, another second learning function 112 is used in the second module 84. The other second learning function 112 determines the operating mode of the vehicle 10 during a current driving cycle. The evaluation within the further, second learning function 112 can include the evaluation of a driving cycle as well as a plurality of driving cycles. The occurring start/stop phases of the vehicle 10 are determined, wherein the vehicle 10 is however not shut down. This results in information concerning the extent to which the vehicle 10 is traveling with frequent start/stop phases, for example in urban traffic, or whether this is less common in the operation of the vehicle 10.

(17) In addition, the data ascertained within the scope of the other second learning function 112 are then used in order to instigate actions in the fuel cell system 22 in the air conveyance subsystem 30 and, if applicable, also with regard to the alternative energy store 26.

(18) Starting from the vehicle “off” state (cf. position 86), in which the vehicle 10 is shut off, the first learning function 90 becomes active in order, if necessary, to take external data with regard to the determination of the operating mode of the vehicle 10 under consideration, thereby using an integrated network data exchange 92. If the determination results in that no “delivery mode” 94 is present, the call up of a standard shutdown routine 98 for the fuel cell system 22 of the vehicle 10 takes place.

(19) If, on the other hand, the existence of the “delivery mode” 94 is detected in the first learning function 90, a plurality of options exist in the context of determining the operating mode of vehicle 10:

(20) As a first action, the shutdown of the fuel cell system 22 can be delayed; this continues after the vehicle 10 has been parked for a certain period of time during the extra running time. The fuel cell system 22, like the air conveyance subsystem 30 as well, can be further operated when idling, thereby generating an electrical idling power. From the running time extension 100 of the fuel cell system 22, a branch-off to a state of charge query 104 can be carried out, within which, the state of charge (SOC) of the at least one alternative energy store 26 is queried. As long as the maximum of the SOCs has not been achieved, the electrical idling power, which is generated during the extra running time of the fuel cell system 22, can be fed into the alternative energy store 26 until this is full or almost full. Only then can auxiliary consumers 110 be switched on or, if the electrical idling power generated when the fuel cell system 22 is idling cannot be taken, a bleed-down action 108 takes place, within which the air conveyance subsystem 30 is shut down and remaining oxygen is consumed on the cathode side of the fuel cell stack 50.

(21) If, the operating mode “delivery mode” 94 is detected within the scope of the first learning function 90 with regard to the operating mode of the vehicle state of the vehicle 10, a second action can be instigated, according to which a running time extension 102 of the air conveyance subsystem 30 is initiated. The air conveyance subsystem 30 is further operated here at minimum power with a minimum rotational speed. The minimum rotational speed is preferably just above the limit rotational speed for the gas bearings used. The limit rotational speed of the gas bearings used is determined by the formation of the aerostatic pressure pad in these, below which a shaft can no longer be centered in a contactless manner, i.e. solid-body contact occurs, which, however, must absolutely be avoided. During the extra running time of the air conveyance subsystem 30, the pressure control valve 34 shown in FIG. 1 is completely opened, so that an air conveyance is given at very low pressure and minimum load; furthermore, the bypass valve 32, (cf. the illustration of FIG. 1), is completely opened to guide the air-mass flow completely past the fuel cell stack 50. The air conveyance subsystem 30 can thus be further operated with a minimal level of power dissipation, which can be taken, for example, from the alternative energy store 26, for some time, in particular lying in the minute range, whereby the extra running time is also prolonged. With a minimum load, i.e. idling during the extra running time, the noise emissions of the components of the fuel cell system 22 or the components of the air conveyance subsystem 30 are also minimized.

(22) In this context, it is noted that it is essential that the opening pressure of the stop valve 36, which is arranged on the inflow side in front of the fuel cell stack 50, is designed so that the opening pressure is slightly above the minimum pressure that is generated by the minimum air compression of the air conveyance subsystem 30. In any case, it must be ensured that no more air enters the fuel cell stack 50 in this operating state.

(23) For systems without a bypass in the air path around the fuel cell stack 50, the air flow in idling mode must be led through the fuel cell stack 50. This is not optimal, but must be taken into consideration within certain limits in terms of water management, restarts and other conditions. The presence of a bypass is advantageous for the implementation of the method proposed according to the invention for reducing the start/stop operations, but not a mandatory condition for the proposed learning methods.

(24) Starting from the vehicle “on” state (cf. position 88) (idling), in the other second learning function 112, the operating mode of the vehicle 10 during at least one driving cycle or also a plurality of driving cycles is determined with regard to occurring start/stop phases, wherein, however, the vehicle 10 is not shut down. Within the scope of the further second learning function 112, a stop-phase determination 114 is carried out. Analogously to the first learning function 90, the other second learning function 112 can also take into consideration data from a navigation system or, for example, a cloud during the determination of the operating mode of the vehicle 10 during its journey via an integrated data exchange 92. If it turns out that in the context of a stop-phase determination 114 stop phases frequently occur, for example, an adjustment of the range for the state of charge SOC of at least one alternative energy store 26 can be performed. The state-of-charge range for the at least one alternative energy store 26 can be somewhat lowered in the driving area so that the operation, meaning the extra running time of the fuel cell system 22, can be prolonged for a temporary shutdown phase.

(25) If more frequent stop phases occur in the vehicle state 88, the fuel cell system 22 initially continues at the lowest level of load or idling when a stop phase occurs. The electrical idle power generated within the scope of the idling of the fuel cell system 22 can, to the extent possible, be fed into the at least one alternative energy store 26 as long as its state of charge (SOC) has not reached its maximum. If, on the other hand, the maximum state of charge SOC of at least one alternative energy store 26 is reached, either a bleed-down action 108, i.e. a shutdown of the air supply of the fuel cell system 22, can take place and remaining oxygen can react in the cathode. Alternatively, it is also possible to switch on additional consumer devices 110 in order to take away the electrical idle power generated during the extra running time 106 of the fuel cell system 22 during a stop phase of the vehicle 10.

(26) While the extra running time 106 of the air conveyance subsystem 30 as described above represents a second option for action, a third option for action is to activate additional consumer devices 110. This is suitable, for example, if within the scope of the option for action 1, the state of charge SOC of the alternative energy store 26 has reached its maximum, thereby being fully or almost fully charged. It is then possible to switch on additional consumer devices 110, provided that these can be used in a useful way. For example, as part of switching on possible additional consumer devices 110, a charging of the conventional 12-volt vehicle battery 28 could be carried out, furthermore, actuator controls for plausibility and test functions could be carried out.

(27) With this third action, switching on additional consumer devices 110, the extra running time phase of the fuel cell system 22 can be extended once again.

(28) The other option for action is the idling operation of the air system via the bypass or through the fuel cell stack 50 in the case that that very bypass should not be present in a topology of the fuel cell system 22 without a bypass.

(29) Within the scope of the integrated network data exchange 92, in the two learning functions described above 90 and 112 navigation data of a navigation system or navigation data of integrated network vehicles (car-to-car, car-to-infrastructure) can be correspondingly detailed and further optimized. For example, certain start/stop phases can already be included in the operational strategy for reducing start/stop operations in the forecast, such as emerging traffic congestion situations. The set destination, which is available in the context of the navigation data of a navigation system, can also be taken into account. If the target is achieved, the fuel cell system 22 or the air conveyance subsystem 30 can be completely shut down. If, on the contrary, the destination has not been reached, the extra running time phase of the fuel cell system 22 and/or the air conveyance subsystem 30 can be somewhat extended. When determining the operating strategy for the vehicle 10 with a mobile fuel cell system 22 and at least one alternative energy store 26, for example, other input parameters such as the ambient temperature, air humidity and more of the like can be taken under consideration. Furthermore, it must be mentioned that, for the case that the vehicle 10 is operated in the “delivery mode” 94, at low exterior temperatures, a part of the idling power generated when the fuel cell system 22 and the air conveyance subsystem 30 are idling can be used for heating the passenger compartment within the scope of a comfort function.

(30) Alternatively, the functions can also be carried out outside of the vehicle 10 on a server and only the actuator control system and the sensor values can be exchanged via corresponding car-to-infrastructure interfaces.

(31) The invention is not limited to the exemplary embodiments described herein and the aspects highlighted herein. Rather, within the range indicated by the claims, a large number of variations are possible, which are within the scope of professional action.