Control method for controlling a brief, temporary power reduction of a fuel cell system

Abstract

The present invention relates to a control method for controlling a brief, temporary power reduction of a fuel cell system (100), wherein the following steps are provided: - sensing a reduction requirement (RA) for the brief, temporary power reduction for the fuel cell system (100), - reducing the operating current (BI) of the fuel cell system (100) to a no-load current value (LI), - operating at least one operating component (B) of the fuel cell system (100) with an unreduced electrical component operating power (KBL).

Description

[0001] Control procedure for controlling a short-term, temporary power reduction of a fuel cell system

[0002] The present invention relates to a control method for controlling a short-term, temporary power reduction of a fuel cell system, a computer program product for carrying out such a control method, a control device for carrying out such a control method and a fuel cell system with such a control device.

[0003] It is known that fuel cell systems are and should be used to generate electrical energy, particularly for powering vehicles. It should be noted that, in addition to varying load requirements, a fuel cell system may also require very rapid load reduction in special situations. If a fuel cell system is used in vehicles, for example, the electrical power currently produced by the fuel cell system can significantly exceed the current load requirement during wheel spin, a short downhill descent, or a sudden braking maneuver.

[0004] A disadvantage of the known solutions is that the variability and control flexibility of fuel cell systems is relatively low, meaning that a relatively sluggish normal operating mode prevails. If a reduction in the power of the fuel cell system is necessary over a certain period of time, in particular to almost 0, existing systems must be put into a so-called idle mode, which is also referred to as the open-circuit state. However, even in such an open-circuit state, a certain amount of electrical power is generated, which must be temporarily stored, for example, in a battery. This open-circuit state can only be used for a certain period of time, after which the fuel cell system must be transferred to a completely off state. Known fuel cell systems are therefore often switched off completely and must then be restarted, i.e. started up, to generate electrical power.

[0005] The object of the present invention is to at least partially remedy the disadvantages described above. In particular, the object of the present invention is to provide a cost-effective and simple way to react quickly to sudden load reductions in a fuel cell system.

[0006] The above object is achieved by a control method having the features of claim 1, a computer program product having the features of claim 12, a control device having the features of claim 13, and a fuel cell system having the features of claim 14. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the control method according to the invention naturally also apply in connection with the computer program product according to the invention, the control device according to the invention, and the fuel cell system according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made reciprocally.

[0007] According to the invention, a control method is proposed for controlling a short-term, temporary power reduction of a fuel cell system. Such a control method is characterized by the following steps:

[0008] - Recording a reduction request for a short-term, temporary power reduction for the fuel cell system,

[0009] - Reduction of the operating current of the fuel cell system to an idle current value,

[0010] - Operating at least one operating component of the fuel cell system with unreduced electrical component operating power.

[0011] A control method according to the invention will, in particular, form part of a normal operational control method for a fuel cell system. This control method according to the invention is based on the detection of a reduction request. This can be actively generated by other parts of a control module. If the fuel cell system is used, for example, to drive a vehicle, the vehicle's wheels may spin due to the environmental conditions. If this is the case, a corresponding driving control can issue a reduction request within the meaning of the present invention, which is detected by the control method. It should be noted that the reduction request is a short-term and temporary power reduction for the fuel cell system. A short-term power reduction is understood to mean the fastest possible reduction.While fuel cell systems are typically ramped up and down to control their normal operation, a short-term reduction in power can also be understood as a sudden or even immediate reduction in power, in contrast to this ramp-like change in the power situation. A temporary power reduction is understood to be a limited period of time over which this power reduction lasts. A permanent power reduction, for example, when parking the vehicle or during a prolonged power reduction with a correspondingly long downhill ride, must be distinguished from a short-term, temporary power reduction according to the present invention.

[0012] As soon as a control method according to the invention has detected such a reduction request for a short-term, temporary power reduction, two subsequent steps are triggered. These following steps can be carried out one after the other or in parallel. Firstly, the operating current of the fuel cell system is reduced to an idle current value. This idle current value is, in particular, lower than the usual current value under load for the fuel cell system. Preferably, this idle current value is in the range just above or close to 0 amperes, but not exactly 0 amperes. In other words, the operating current of the fuel cell system is regulated down, but not set to 0, so that switching off and thus also shutting down the fuel cell system is not necessary.In addition, it seems important not to further reduce the operating current so that cell voltage does not become too high, which can promote degradation.

[0013] The second step involves operating at least one operating component of the fuel cell system with unreduced electrical component operating power. Normal operation would result in all operating components of the fuel cell system also switching to idle mode during idle operation. If no electrical power is required in an idle situation during normal operation of a fuel cell system, all operating components, such as heaters, blowers, compressors, and the like, can also be placed into a corresponding idle state, in which they consume only very little electricity. This typically serves to conserve the vehicle's electrical storage resources during idle operation and prevent unnecessary energy consumption.

[0014] According to the invention, the control method according to the invention is designed in particular for controlling a short-term, temporary power reduction of a PEM fuel cell system.

[0015] Within the scope of the present invention, however, action is taken contrary to this usual operating strategy. This only occurs, however, if a reduction request for short-term and temporary power reduction has also been detected. Only in this case does the operation of the other operating components of the fuel cell system not reduce in an idle situation, but rather continues operation with unreduced electrical component operating power. Unreduced electrical component operating power essentially refers to two variants. If the operating component is already operating at a defined operating power, it can continue operation with unchanged and thus constant or static electrical component operating power.However, depending on the operating situation when the reduction requirement is detected, it may also be advantageous to increase the electrical component operating power while continuing to operate without reduction.

[0016] Because, in a control method according to the invention, one or more operating components continue to operate with unreduced electrical component operating power, contrary to the usual operating strategy, an electrical consumer is available. Since this represents a temporary and short-term power reduction for the fuel cell system and the operating current is set to the idle current value, the fuel cell system will continue to provide electrical power despite the consumer, in the form of the vehicle, no longer having a short-term, temporary power requirement. Depending on the vehicle's equipment, however, only a small portion of this electrical power can be stored, for example, in a battery device or capacitors.In known solutions, the speed at which the power of the fuel cell system can be reduced is therefore the limiting factor for reducing the output load and thus the reaction speed to the short-term, temporary power reduction.

[0017] A control method according to the invention now makes it possible to provide an electrical load, in the form of continued operation of at least one operating component despite the fuel cell system being idle, which can absorb the continued increased power output of the fuel cell system. In addition to the usual storage functionality of a battery device or existing capacitors, an electrical load can now absorb the electrical energy not required during this short-term, temporary period and use it for operation. This means that a response to the short-term and temporary power reduction can be provided without intervention in the fuel cell system. This response can be significantly more abrupt and thus faster and more flexible than is the case with conventional control methods for fuel cell systems.

[0018] Since a control method according to the invention deals with short-term and temporary power reductions for the fuel cell system, an end signal or an increase request for the end of the short-term, temporary power reduction is preferably also detected in order to transfer the control method for the fuel cell system back to normal operating mode. This clearly shows a further advantage of a control method according to the invention. In contrast to known solutions, despite the rapid and sudden power reduction for the consumer in the form of the vehicle drive, the fuel cell system continues to be kept in an idle state and does not have to be shut down completely. At the end of the short-term, temporary power reduction, the fuel cell system is now available again in idle mode for a flexible and equally rapid or even sudden increase in the power requirement.In contrast to the known solutions, not only the response to the power reduction but also the return to normal operating mode for the fuel cell system is significantly improved.

[0019] It can be advantageous if, in a control method according to the invention, the reduction request is implemented as a step-like reduction request. This step-like reduction request is to be understood in particular as a gradual reduction, particularly with a single step, for reducing the power requirement. In other words, in contrast to following a ramp-like reduction of the reduced power requirement, the reduction request is implemented in a step-like manner, thus providing the flexibility that is only guaranteed by a control method according to the invention.

[0020] Furthermore, it is advantageous if, in a control method according to the invention, the operating component continues to be operated at a constant or essentially constant component operating power. As already explained in the introduction, there are essentially two basic operating options for the operating component. One of these two variants is mentioned here. In particular, it is checked whether the remaining residual power output of the fuel cell system can also be consumed by the operating component at the current operating power, so to speak, as reduced consumption. If this is the case, the current component operating power of the selected operating component and the necessary residual power of the fuel cell system as reduced consumption are equal, so that the operating component can simply continue to be operated at the existing component operating power.This is particularly the case when the remaining power output of the fuel cell system is low and / or the previous operating power of the operating component is correspondingly high. It is already clearly evident that the previous operating situation before the reduction requirement is recorded influences the actual implementation of the operating component's operation.

[0021] It also offers advantages if, in a control method according to the invention, the operating component continues to operate at an increased component operating power. This represents an alternative or additional embodiment to the previous paragraph. It should be noted here that, of course, two or more operating components can also provide this continued operation step and can continue to be operated accordingly with identical or different strategies regarding the unreduced electrical component operating power. Increasing the component operating power leads to a corresponding increase in power consumption and correlates in particular with the necessary reduced consumption based on the continued operation of the fuel cell system, which will be explained in more detail later.

[0022] Furthermore, it is also advantageous if, in a control method according to the invention, a necessary reduction in consumption for the fuel cell system is determined after the operating current has been reduced to the idle current value. In particular, the electrical component operating power is checked and / or adjusted to the determined reduction in consumption. While control in the form of simple control without feedback information is also possible, in the form of specifying a defined component operating power, the integration of information on a necessary reduction in consumption can further improve the method according to the invention.In particular, this makes it possible to ensure, in a controlled, preferably regulated manner, that the determined reduction consumption of the fuel cell system can actually be absorbed by the consumers in the form of the at least one operating component. In particular, it is also taken into account which portion of the remaining reduction consumption can be consumed by other components, in particular storage components such as a battery storage device.

[0023] Further advantages can be achieved if, in a control method according to the invention, at least two operating components are operated at unreduced component operating power. Depending on the actual application situation and the selected operating components, it may sometimes not be sufficient for the remaining possible component operating power of a single operating component to actually absorb the necessary reduced consumption. In such a case, two or more operating components can continue to operate together at unreduced component operating power in order to connect as many consumers as are actually necessary for the determined reduced consumption.

[0024] It can be advantageous if, in a control method according to the invention, at least one operating component is selected from a set of several operating components, in particular taking a reduction priority into account. For example, individual operating components can have different component operating powers and also different degrees of freedom in which they are operated. For example, on the air side of a fuel cell system, there can be greater freedom with regard to the operating mode of an air blower than, for example, on the fuel side, in particular for a recirculation blower or a fuel blower. In this way, such functional priorities and / or degrees of freedom can be taken into account in order to be able to ensure the selection of the operating component to be operated further in an optimized manner for the fuel cell system within the framework of the present control method.

[0025] Furthermore, it is advantageous if, in a control method according to the invention, the at least one operating component is at least one of the following:

[0026] - blower device,

[0027] - compressor device,

[0028] - Heating device.

[0029] The above list is not exhaustive. Of course, other operating components, in particular secondary operating components, of a fuel cell system can also be taken into account in a control method according to the invention.

[0030] Further advantages are achieved if, in a control method according to the invention, the fuel supply to the fuel cell system is reduced for the duration of the reduced operating current. An alternative to reducing the fuel supply is to increase the recirculation in order to achieve the lowest possible idle current.

[0031] It is also advantageous if, in a control method according to the invention, at least one valve device in the fuel cell system is temporarily closed to create an increased backpressure and a concomitant additional increase in the electrical component operating power. In other words, it becomes possible to block fluid flows within the fuel cell system or at least increase their flow resistance, thus providing an increased backpressure. If a compressor device is selected as an operating component for continued operation, for example on the air side of the fuel cell system, the technically possible consumption of this compressor device in the form of the electrical component operating power can be easily increased by increasing the backpressure by closing or partially closing corresponding valves arranged downstream.A pulsating closing and opening of these valve devices can also be part of a control method according to the invention.

[0032] It is also advantageous if, in a control method according to the invention, the reduction requirement is based on at least one of the following events when using the fuel cell system in a vehicle:

[0033] - Spin of the vehicle's wheels,

[0034] - short-term downward trend,

[0035] - short-term braking.

[0036] The above list is not exhaustive. Of course, combinations of different reduction requirements may also arise, and a control method according to the invention may also offer advantages when used for purposes other than vehicles.

[0037] A further subject of the present invention is a computer program product comprising instructions which, when executed by a computer, cause the computer to perform a control method according to the invention. Thus, a computer program product according to the invention also provides the same advantages as those explained in detail with reference to a control method according to the invention.

[0038] The present invention also relates to a control device for controlling a short-term, temporary power reduction of a fuel cell system, wherein the fuel cell system is designed in particular as a PEM fuel cell system. Such a control device is characterized by a detection module for detecting a reduction request for a short-term, temporary power reduction for the fuel cell system. Furthermore, a reduction module is provided for reducing the operating current of the fuel cell system to an idle current value. With the aid of an operating module, at least one operating component of the fuel cell system is operated with unreduced electrical component operating power. The detection module, the reduction module, and / or the operating module are designed for carrying out a control method according to the invention.

[0039] A control device according to the invention thus brings with it the same advantages as have been explained in detail with reference to a control method according to the invention.

[0040] Furthermore, the present invention also relates to a fuel cell system for generating electrical power, in particular for operating a vehicle, wherein the fuel cell system is designed in particular as a PEM fuel cell system. According to the invention, the vehicle can be, for example, a car, truck, off-road vehicle, ship, train, or aircraft. Such a fuel cell system has a fuel cell stack with an anode section and a cathode section. The anode section is equipped with an anode feed section for supplying anode feed gas and an anode discharge section for discharging anode exhaust gas. Similarly, the cathode section is equipped with a cathode feed section for supplying cathode feed gas and a cathode discharge section for discharging cathode exhaust gas.Furthermore, this fuel cell system also has, in particular, a recirculation section for feeding a portion of the anode exhaust gas back to the anode supply section and thus to the anode section. Such a fuel cell system is characterized in that a control device of the present invention is provided for controlling at least one operating component of the fuel cell system. Thus, such a fuel cell system also offers the same advantages as those explained in detail with reference to a control method according to the invention.

[0041] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. They show schematically:

[0042] Fig. 1 shows an embodiment of a fuel cell system according to the invention, Fig. 2 shows an embodiment of a control device according to the invention,

[0043] Fig. 3 a possible course of the individual parameters,

[0044] Fig. 4 another possible course of the individual parameters,

[0045] Fig. 5 another possible course of the individual parameters,

[0046] Fig. 6 another possible course of the individual parameters and

[0047] Fig. 7 shows a further embodiment of a control device according to the invention.

[0048] Figure 1 schematically shows a fuel cell system 100. It is illustrated here with a fuel cell stack 110. This fuel cell stack 110 has an anode section 120 and a cathode section 130. Anode feed gas AZG is supplied to the anode section 120 via an anode feed section 122. Cathode feed gas KZG is supplied to the cathode section 130 via a cathode feed section 132. After the chemical reaction and generation of electrical energy, the anode exhaust gas AAG is removed via the anode discharge section 124, and the cathode exhaust gas KAG is removed via the cathode discharge section 134. In particular, a recirculation section can also be provided, which in particular connects the anode discharge section 124 to the anode feed section 122 in order to partially feed the anode exhaust gas back to the anode section 120 (this is not shown in Fig. 1, however).Schematically shown here are a blower device 140 in the anode supply section 122, and a compressor 150 and an electric heating device 160 in the cathode supply section 132. However, heating device 160 is preferably arranged in a cooling system of the fuel cell system 100 (not shown in Fig. 1). These three components represent examples of operating components B of the fuel cell system 100.

[0049] Figure 2 schematically shows a control device 10. This control device 10 is equipped with a detection module 20, which detects a reduction request RA. This can be based, for example, on spinning wheels of a vehicle for which the fuel cell system 100 is used as a drive. This reduction request RA is forwarded from the detection module 20 to the reduction module 30, which then reduces the operating current BI to an idle current value LI. In addition, at least one operating component B continues to operate with an unreduced component operating power KBL with the aid of the operating module 40, either in parallel or subsequently. The type of reduction is illustrated in more detail in Figures 3 and 4, for example.

[0050] Figure 3 shows the correlation between operating current BI and component operating power KBL. In order to be able to absorb and consume the remaining power in idle operation below the idle current value LI despite the reduced load requirements, the corresponding operating component B is operated with an increased component operating power KBL. As Figure 4 shows, the reduction requirement RA is a sudden drop in the operating current BI and a temporary and therefore time-limited duration of this reduction requirement RA. In other words, after the end of the reduction requirement RA, not only is the operating current BI increased again from the idle current value LI, but the component operating power KBL is also reduced to its previous value.

[0051] Figures 5 and 6 show a similar situation to Figures 3 and 4. However, in this case, it is sufficient to consume the reduced consumption RV of the fuel cell system 100 if the corresponding operating component B continues to operate at a constant component operating power KBL. Accordingly, according to Figure 6, the operating current BI is temporarily reduced to the idle current value LI via the reduction requirement RI, but the component operating power KBL can also continue to be operated at a constant level via the reduction requirement RA.

[0052] Figure 7 schematically illustrates that a reduced consumption RV is also taken into account. In particular, in this variant, the reduced consumption RV is so large that two operating components B are now selected to provide the necessary electrical component operating power KBL in combination to consume this increased reduced consumption RV.

[0053] The above explanation of the embodiments describes the present invention exclusively by way of examples. List of reference symbols

[0054] 10 Control device

[0055] 20 Recording module

[0056] 30 Reduction module

[0057] 40 Operating module

[0058] 100 fuel cell system

[0059] 110 fuel cell stacks

[0060] 120 anode section

[0061] 122 Anode feed section

[0062] 124 Anode discharge section

[0063] 130 Cathode section

[0064] 132 Cathode feed section

[0065] 134 Cathode discharge section

[0066] 140 Blower device

[0067] 150 compressor device

[0068] 160 heater

[0069] B Operating component

[0070] RA reduction requirement

[0071] RV reduction consumption

[0072] BI operating current

[0073] LI no-load current value

[0074] KBL component operating performance

[0075] AZG anode feed gas

[0076] AAG anode exhaust gas

[0077] KZG cathode feed gas

[0078] KAG cathode exhaust gas

Claims

Patent claims 1. Control method for controlling a short-term, temporary power reduction of a fuel cell system (100), characterized by the following steps: - Recording a reduction request (RA) for a short-term, temporary power reduction for the fuel cell system (100), - Reduction of the operating current (BI) of the fuel cell system (100) to an idle current value (LI), - Operating at least one operating component (B) of the fuel cell system (100) with unreduced electrical component operating power (KBL).

2. Control method according to claim 1, characterized in that the reduction request (RA) is designed as a sudden reduction request (RA).

3. Control method according to one of the preceding claims, characterized in that the operating component (B) continues to be operated with a constant or substantially constant component operating power (KBL).

4. Control method according to one of claims 1 or 2, characterized in that the operating component (B) continues to be operated with increased component operating power (KBL).

5. Control method according to one of the preceding claims, characterized in that a determination of a necessary reduction consumption (RV) for the fuel cell system (100) is carried out after reducing the operating current (BI) to the idle current value (LI), wherein the electrical component operating power (KBL) is adapted to the determined reduction consumption (RV).

6. Control method according to one of the preceding claims, characterized in that at least two operating components (B) are operated with unreduced component operating power (KBL).

7. Control method according to one of the preceding claims, characterized in that the at least one operating component (B) is selected from a set of several operating components (B), in particular taking into account a reduction priority.

8. Control method according to one of the preceding claims, characterized in that the at least one operating component (B) is at least one of the following: - Blower device (140) - Compressor device (150) - Heating device (160) 9. Control method according to one of the preceding claims, characterized in that the supply of fuel in the fuel cell system (100) is reduced for the duration of the reduced operating current (BI).

10. Control method according to one of the preceding claims, characterized in that at least one valve device in the fuel cell system (100) is temporarily closed for an increased back pressure and a concomitant additional increase in the electrical component operating power (KBL).

11. Control method according to one of the preceding claims, characterized in that the reduction request (RA) is based on at least one of the following events when using the fuel cell system (100) in a vehicle: - Wheel spin of the vehicle - Short-term downward trend - Short-term braking 12. A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the steps of a control method having the features of one of claims 1 to 11.

13. Control device (10) for controlling a short-term, temporary power reduction of a fuel cell system (100), characterized by a detection module (20) for detecting a reduction request (RA) for short-term, temporary power reduction for the fuel cell system (100), a reduction module (30) for reducing the operating current (BI) of the fuel cell system (100) to an idle current value (LI), and an operating module (40) for operating at least one operating component (B) of the fuel cell system (100) with unreduced electrical component operating power (KBL), wherein the detection module (20), the reduction module (30), and / or the operating module (40) are designed to carry out a control method having the features of one of claims 1 to 11.

14. A fuel cell system (100) for generating electrical power, in particular for driving a vehicle, comprising a fuel cell stack (110) with an anode section (120) and a cathode section (130), the anode section (120) comprising an anode feed section (122) for feeding anode feed gas (AZG) and an anode discharge section (124) for discharging anode exhaust gas (AAG), the cathode section (130) comprising a cathode feed section (132) for feeding cathode feed gas (KZG) and a cathode discharge section (134) for discharging cathode exhaust gas (KAG), characterized in that a control device (10) with the features of claim 13 is provided for controlling at least one operating component (B) of the fuel cell system (100).

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