Method and device for operating a fuel cell system

Abstract

The invention relates to a device (103) for operating a fuel cell system (100) having a fuel cell stack (102) and an anode subsystem (500) for receiving fuel (211) of the fuel cell stack (102). The device (103) is designed to determine a time curve of the pressure (610) in the anode subsystem (500) during at least one previous purging event (631) for discharging the liquid water (506) from the anode subsystem (500). The device (103) is further designed to determine one or more operating parameters for operating the fuel cell system (100) on the basis of a time curve of the detected pressure (610); the one or more operating parameters for operating the fuel cell system (100) comprise one or more operating parameters relating to the implementation of one or more subsequent purge events (631).

Description

Technical Field

[0001] The technology disclosed herein relates to a method and a corresponding device for operating a fuel cell system, particularly in the case of a purge event considering anode drainage of a fuel cell stack for a fuel cell system. Background Art

[0002] An electrically driven vehicle can have a fuel cell, particularly a fuel cell stack with one or more fuel cells, which is configured to generate electrical energy for operating a drive motor of the vehicle based on a fuel, particularly based on hydrogen. The fuel for the fuel cell stack is typically guided from a pressure vessel to the fuel cell stack. Here, the amount of fuel supplied to the fuel cell stack can be changed by a valve.

[0003] The electrical power provided by the fuel cell stack can be influenced by the amount of fuel supplied to the fuel cell stack. An increase in the supplied amount of fuel typically leads to an increase in the electrical power, which in turn enables an increased drive power of the vehicle.

[0004] On the other hand, supplying an excessive amount of fuel to the fuel cell stack can result in an increase in the concentration of fuel in the exhaust of the fuel cell stack, thereby affecting the energy efficiency of the fuel cell stack. For this reason, it is typically advantageous to adjust the amount of fuel supplied to the fuel cell stack according to the respective current anode state of the anode of the fuel cell stack, particularly according to the respective current fuel concentration on the anode of the fuel cell stack.

[0005] To determine the anode state, particularly to determine the fuel concentration on the anode, dedicated concentration sensors can be used, however, which involve additional costs and additional structural space requirements. Alternatively or additionally, mathematical operating models can be used for the fuel cell stack to estimate the anode state, particularly the fuel concentration. However, the anode state determined according to the operating model may be inaccurate and typically related to the initialization of the operating model. Summary of the Invention

[0006] Here, an advantageous object of the disclosed technology is to reduce or overcome at least one drawback of the previously known solutions or to provide an alternative solution. An advantageous object of the disclosed technology is to determine the fuel concentration on the anode of the fuel cell stack in an efficient and precise manner and / or to adjust it according to optimized values in order to enable efficient and reliable operation of the fuel cell stack.

[0007] This object is solved by the subject matter of the independent claims. The dependent claims are preferred designs.

[0008] An apparatus for operating a fuel cell system is described according to one aspect. The fuel cell system includes a fuel cell stack and an anode subsystem for receiving fuel (in particular hydrogen) for the fuel cell stack. The anode subsystem may include a water separator configured to separate liquid water from the anode exhaust of the fuel cell stack. Additionally, the anode subsystem may include a purge valve configured to discharge the water separated by the water separator from the anode subsystem. The apparatus may be configured to open the purge valve to cause a purge event and thereby discharge liquid water from the anode subsystem.

[0009] The purge event can thereby be used to discharge liquid water from the anode subsystem. Here, one or more operating parameters, such as for example the duration and / or repetition rate of the purge event, can be matched with respect to the purge event. By repeatedly causing the purge event, accumulation of liquid water in the anode of the fuel cell stack can be avoided, as well as the associated insufficient fuel supply to the anode and the associated damage to the anode. On the other hand, causing the purge event too frequently can lead to a reduction in the efficiency of the fuel cell system (since fuel may be discharged through the purge valve). The apparatus described herein may be focused on enabling a particularly energy-efficient and economic operation of the fuel cell system.

[0010] The anode subsystem may be configured such that after a first phase of the purge event (in which substantially only liquid water is discharged from the anode subsystem), fuel is discharged from the anode subsystem in at least one subsequent phase (if the purge event has a total duration exceeding the duration of the first phase). Since discharging fuel can reduce the energy efficiency of the fuel cell system.

[0011] Alternatively or additionally, the anode subsystem may be configured such that during the (second or third) phase of the purge event in which fuel is discharged from the anode subsystem, the pressure of the fuel in the anode inlet line to the anode of the fuel cell stack and / or the pressure of the anode exhaust in the anode exhaust line from the anode (compared to the pressure during the first phase of the purge event) decreases. This pressure drop can be caused by directly discharging the fuel (through the purge valve) from the anode subsystem during this (second or third) phase of the purge event, such that the gas pressure in the anode inlet line and / or in the anode exhaust line decreases. This decrease in gas pressure can be used for the analysis of the purge event.

[0012] The device is set to determine the time curve of the pressure in the anode subsystem (e.g., in the anode inlet line and / or in the anode exhaust line) during at least one previous purge event. The anode subsystem may include at least one pressure sensor configured to detect the pressure of the fuel in the anode inlet line and / or the pressure of the anode exhaust in the anode exhaust line. The device may be set to determine the time curve of the pressure in the anode subsystem during the previous purge event based on the sensor data of the pressure sensor.

[0013] The device is further set to determine one or more operating parameters for operating the fuel cell system (in particular one or more operating parameters regarding the purge of the fuel cell system) based on the detected time curve of the pressure (during the previous purge event). The one or more operating parameters for operating the fuel cell system may include one or more operating parameters regarding the implementation of one or more subsequent purge events. In the case of implementing one or more subsequent purge events (each based on the curve of the pressure detected during the respective previous purge event), a repeated adaptation (e.g., in the form of regulation / closed-loop control) of the one or more operating parameters may be implemented. In this way, the accumulation of liquid water in the anode can be prevented in a particularly efficient and reliable manner.

[0014] The one or more operating parameters of the fuel cell system may in particular include:

[0015] - the duration of at least one subsequent purge event; and / or

[0016] - the time interval between the subsequent purge event and the previous purge event; and / or

[0017] - the repetition rate of one or more subsequent purge events; and / or

[0018] - the opening degree of the purge valve during the subsequent purge event; and / or

[0019] - the value of the pressure in the anode subsystem (in particular in the anode inlet line); and / or

[0020] - the value of the electrical power of the fuel cell stack.

[0021] The device is thus set to analyze the pressure curve in the anode subsystem during the previous purge event in order to adapt the subsequent operation of the fuel cell system. In this way, a particularly efficient, reliable and economical operation of the fuel cell system can be achieved. In particular, an insufficient fuel supply in the anode of the fuel cell stack can be avoided in a reliable manner. In addition, excessive fuel consumption can be avoided in this way.

[0022] The device can be set to determine, based on a time curve of pressure, whether the previous purge event included at least one (second or third) phase in which fuel was discharged from the anode subsystem. Then, one or more operating parameters for operating the fuel cell system can be determined in a particularly efficient and reliable manner based on whether the previous purge event included at least one phase in which fuel was discharged from the anode subsystem.

[0023] The device can be set to determine one or more characteristics of the previous purge event based on a time curve of pressure. The one or more characteristics can be determined by one or more comparisons of the time-pressure curve with one or more pressure thresholds. The one or more characteristics can include:

[0024] - The fact that the previous purge event included only the first phase, in which only water was discharged from the anode subsystem substantially;

[0025] - The fact that the previous purge event included, in addition to the first phase, a second phase, in which in addition to water, fuel was also discharged from the anode subsystem;

[0026] - The fact that the previous purge event included, in addition to the second phase, a third phase, in which substantially only fuel was discharged from the anode subsystem; and / or

[0027] -- The duration of the first phase, the second phase, and / or the third phase.

[0028] Then, one or more operating parameters for operating the fuel cell system can be determined and / or adapted in a particularly efficient and accurate manner based on the one or more characteristics of the previous purge event.

[0029] The device can be set to compare the time curve of pressure with at least one pressure threshold. Then, one or more operating parameters for operating the fuel cell system can be determined based on this comparison.

[0030] The device can in particular be set to compare the time curve of pressure with a first pressure threshold. By this comparison, it can be determined whether the previous purge event (in addition to the first phase) included a second phase, in which in addition to water, fuel was also discharged from the anode subsystem. Furthermore, the duration of the second phase can be determined.

[0031] In addition, the device can be set to compare the time curve of the pressure with a second pressure threshold, where the second pressure threshold is less than the first pressure threshold. Thereby, it can be determined whether the previous purge event (except for the first and second phases) includes a third phase, in which only fuel is discharged from the anode subsystem substantially. In addition, the duration of the third phase can be determined.

[0032] One or more characteristics of the previous purge event can be determined in a particularly efficient and precise manner by applying one or more threshold comparisons.

[0033] As described above, one or more operating parameters for the subsequent operation of the fuel cell system can be determined and / or adapted based on the one or more characteristics of the previous purge event. The device can be set such that if the previous purge event includes only the first phase, then the duration and / or repetition rate of one or more subsequent purge events is increased and / or the time interval between one or more subsequent purge events is decreased. In this way, the risk of insufficient fuel supply can be reduced. Alternatively or additionally, the device can be set such that if the previous purge event includes the third phase, then the duration and / or repetition rate of one or more subsequent purge events is decreased and / or the time interval between one or more subsequent purge events is increased. In this way, the energy efficiency of the fuel cell system can be increased.

[0034] The measures described herein can be repeated over time. Here, one or more previous purge events can be analyzed based on the respective pressure curves. The subsequent operation of the fuel cell system can be adapted based on the analysis of the one or more previous purge events. In this way, a durable, efficient and reliable operation can be achieved.

[0035] The device can be set to determine the one or more operating parameters for operating the fuel cell system such that the duration of the (second) phase in which fuel is discharged from the anode subsystem during at least one subsequent purge event has a determined nominal value (e.g., zero or close to zero). In particular, an adjustment can be caused in which one or more operating parameters are repeatedly adapted based on the time-pressure curve of one or more previous purge events such that the duration of the second phase of one or more subsequent purge events is set, in particular adjusted, to a determined nominal value. In this way, a particularly efficient and reliable operation of the fuel cell system can be achieved.

[0036] External (dynamic) events can occur during the operation of a fuel cell system, thereby affecting the pressure (in the anode inlet line and / or in the anode exhaust line). This can be the case especially when the fuel cell system is operating in a motor vehicle. It can happen that such external events occur during a purge event and thus cause a distortion of the pressure-time curve required for the purge event.

[0037] The device can be set up to check whether the time curve of the pressure detected for the previous purge event, in particular based on external dynamic events, is distorted. For this purpose, the time curve of the pressure can be compared with one or more reference curves (for a non-distorted pressure curve). Classification can thus be achieved as to whether the time curve of the pressure required for the purge event is distorted or not.

[0038] Then, when determining the one or more operating parameters for operating the fuel cell system, the time curve of the detected pressure can be considered depending on whether the time curve of the detected pressure is identified (i.e., classified) as distorted. In particular, the form of consideration of the time curve of the pressure can be adapted depending on whether the time curve of the detected pressure is identified (i.e., classified) as distorted.

[0039] By identifying and taking into account the distorted time-pressure curve, the operating reliability of the fuel system can be further improved. The device can be set up, for example, such that if it is identified or classified that the time curve of the pressure detected for the previous purge event is distorted, then it is generally determined that the previous purge event does not have a phase in which fuel is discharged from the anode subsystem (i.e., the purge event only has the first phase). In this way, the operating reliability of the fuel system can be improved in a particularly efficient manner.

[0040] According to another aspect, a fuel cell system is described, which fuel cell system includes the device described herein.

[0041] According to another aspect, a (road) motor vehicle (in particular a passenger car or a goods vehicle or a bus or a motorcycle) is described, which motor vehicle includes the device described herein and / or the fuel cell system described herein.

[0042] According to another aspect, a method for operating a fuel cell system is described, wherein the fuel cell system has a fuel cell stack and an anode subsystem for receiving fuel of the fuel cell stack. The method includes: determining a time curve of the pressure in the anode subsystem during at least one previous purge event (for discharging liquid water from the anode subsystem). The method further includes: determining one or more operating parameters for operating the fuel cell system based on the detected time curve of the pressure. The one or more operating parameters for operating the fuel cell system may include one or more operating parameters for performing one or more subsequent purge events.

[0043] According to another aspect, a software (SW) program is described. The SW program may be configured to be implemented on a processor (e.g., on a control device of a vehicle) and thereby implement the method described herein.

[0044] According to another aspect, a storage medium is described. The storage medium may include an SW program that is configured to be implemented on a processor and thereby implement the method described herein.

[0045] It should be noted that the methods, devices, and systems described herein can be applied not only individually but also in combination with other methods, devices, and systems described herein. In addition, each aspect of the methods, devices, and systems described herein can be combined with each other in various ways. In particular, the features of the respective claims can be combined with each other in various ways. In addition, the features listed in parentheses should be understood as optional features. Description of the Drawings

[0046] Furthermore, the present invention is further described according to embodiments. The drawings show:

[0047] Figure 1 An exemplary fuel cell system with a fuel cell stack is shown;

[0048] Figure 2 An exemplary structure of a fuel cell is shown;

[0049] Figure 3 A side view of an exemplary fuel cell stack is shown;

[0050] Figure 4 A front view of an exemplary fuel cell stack is shown;

[0051] Figure 5 An exemplary anode subsystem of a fuel cell stack is shown;

[0052] Figure 6a An exemplary time curve of the pressure at the anode input or at the anode discharge of a fuel cell stack is shown;

[0053] Figure 6b Illustrate an exemplary chronological order of a purge event during the operation of a fuel cell stack; and

[0054] Figure 7 Illustrate a flowchart of an exemplary method for operating a fuel cell stack. DETAILED DESCRIPTION

[0055] As described above, the present disclosure is directed to enabling efficient and safe operation of a fuel cell stack, particularly with respect to supplying fuel to the anode of the fuel cell stack.

[0056] Figure 1 Illustrate a fuel cell system 100, including a fuel cell stack 102 with at least one fuel cell 101. The fuel cell system 100 is contemplated, for example, for mobile applications such as motor vehicles, particularly for providing energy for at least one drive motor for the forward movement of a motor vehicle. The fuel cell 101 is an electrochemical energy converter that converts fuel and an oxidant into reaction products and generates electricity and heat therewith. The fuel cell 101 includes (as shown in Figure 2 ) an anode 201 and a cathode 202, which are separated by an ion-selective or ion-permeable separator 203. The anode 201 is supplied with fuel 211. Preferred fuels 211 are: hydrogen (H 2 ), low molecular weight ethanol, biofuel, or liquefied natural gas. The cathode 202 is supplied with an oxidant 212. Preferred oxidants 212 are: air, oxygen, and peroxide. The ion-selective separator 203 can be configured, for example, as a proton exchange membrane (PEM). Preferably, a cation-selective polymer electrolyte membrane is employed. Materials for such a membrane are, for example and

[0057] The fuel cell system 100 includes, in addition to at least one fuel cell 101, peripheral system components (Balance-of-Plant (BOP) components), which can be used in the operation of the at least one fuel cell 101. Typically, multiple fuel cells 101 are combined into a fuel cell stack or stack 102. In addition, the fuel cell system 100 typically includes at least one pressure vessel, particularly a pressure tank 110, which is used to provide fuel 211 for one or more fuel cells 101. The pressure vessel 110 is connected to one or more fuel cells 101 by one or more pipelines 112.

[0058] The anode 201 and the cathode 202 of the fuel cell 101, or rather the fuel cell stack 102, can be connected to the contact member 204. An operating voltage (for example, approximately 1 V for the fuel cell 101) is typically applied between the contact members 204, and current can be provided. The operating voltage of the fuel cell stack 102 can be increased by connecting a plurality of fuel cells 101 in series (that is to say, by providing a stack or rather a fuel cell stack 102).

[0059] The fuel cells 101 of the fuel cell stack 102 typically each include two separator plates (not shown). The ion-selective separator 203 of the fuel cell 101 is typically disposed between the two separator plates. One separator plate together with the ion-selective separator 203 constitutes the anode 201. Another separator plate disposed on the opposite side of the ion-selective separator 203 simultaneously constitutes the cathode 202 together with the ion-selective separator 203. Gas channels for the fuel 211 or rather for the oxidant 212 are preferably provided in the separator plates.

[0060] The separator plates can be configured as single plates and / or bipolar plates. In other words, the separator plates advantageously have two sides, where one side together with the ion-selective separator 203 constitutes the anode 201 of the first fuel cell 101, and where the second side together with another ion-selective separator 203 of an adjacent second fuel cell 101 constitutes the cathode 202 of the second fuel cell 101.

[0061] A so-called gas diffusion layer or rather a gas diffusion laminate (GDL) is typically also provided between the ion-selective separator 203 and the separator plate.

[0062] Figure 3 A side view showing the structure of an exemplary fuel cell stack 102 is shown. The fuel cell stack 102 includes end plates 301, and a plurality of fuel cells 101 are provided between the end plates. The end plates 301 can be used to hold or rather press the fuel cells 101 of the fuel cell stack 102 together. As described above, the fuel cell 101 can be formed by one side of each of two adjacent bipolar plates 303. An electrode-membrane unit (Membrane Electrode Assembly, MEA) 304 can be provided between two adjacent bipolar plates 303, which optionally includes the above-mentioned gas diffusion layer. In addition, the fuel cell stack 102 includes a pipeline 302, through which the fuel 211 and / or the oxidant 212 can be guided to the respective fuel cells 101 through the bipolar plates 303, and one or more reaction products can be guided from the respective fuel cells 101 (again through the bipolar plates 303).

[0063] The inlets to the respective pipelines 302 are typically only located on one side of the fuel cell stack 102 in order to reduce the structural space.Figure 4 A front view of an exemplary fuel cell stack 102 is shown. In particular, Figure 4 The end plate 301 of the fuel cell stack 102 is shown, on which there are inlets for the different lines 302 of the fuel cell stack 102. The fuel cell stack 102 may have a fuel cell input line 401 (also referred to as an anode input line), through which the fuel 211 can be guided to the individual fuel cells 101. In addition, the fuel cell stack 102 may have an oxidant input line 402, through which the oxidant 212 can be guided to the individual fuel cells 101. In addition, the fuel cell stack 102 may have a reaction product discharge line 403, through which the reaction products of the fuel cell 101 can be discharged (for example together with excess oxidant 212 or air). In addition, the fuel cell stack 102 may have a fuel discharge line 404 (also referred to as an anode discharge line), through which unconsumed fuel 211 can be discharged from the fuel cell 101 (for example within the scope of anode flushing or within the scope of fuel recirculation).

[0064] Fuel cell system 100 - as exemplified in Figure 5 As shown in the figure - it includes an anode subsystem 500 (including one or more anode-side components), which is composed of structural parts for conducting fuel of the fuel cell system 100. The anode subsystem 500 can have at least one anode input line 401 (composed of at least one pressure vessel 110, at least one tank shut-off valve (=TAV) and, if necessary, at least one pressure reducer) leading to the anode inlet, an anode space in the fuel cell stack 102, at least one anode exhaust line 404 leading away from the anode outlet, at least one water separator 503 (=AWS), at least one anode purge valve 507 (=APV) (also called purge valve), at least one active or passive fuel recirculation conveyor 504 (=ARE or ARB) and / or at least one recirculation line 502 and, if necessary, additional elements. Figure 5 In the example shown in , the anode subsystem 500 has a collecting container 505 for receiving water 506 , which is designed to receive the water 506 from the water separator 503 .

[0065] The primary tasks of the anode subsystem 500 are to direct and distribute the fuel 211 to the electrochemically active surfaces of the anode space and to conduct the anode exhaust gas.

[0066] In addition, the fuel cell system 100 includes a cathode subsystem (including one or more components on the cathode side). The cathode subsystem is formed by a structural member that guides the oxidant. The cathode subsystem may have at least one oxidant transporter 205, at least one cathode inlet line 402 that leads to the cathode inlet, at least one cathode exhaust line 403 that is led away from the cathode outlet, the cathode space in the fuel cell stack 102, and additional elements. The main task of the cathode subsystem is to guide and distribute the oxidant 212 to the electrochemically active surface of the cathode space and to discharge the unused oxidant 212 and / or reaction products.

[0067] As described above, the amount of fuel 211 supplied to the anode space of the fuel cell stack 102 can be matched in order to match the electrical power provided by the fuel cell system 100. Here, the current anode state, that is, in particular the current fuel concentration of the gas mixture in the anode space of the fuel cell stack 102, can be taken into account so that the amount of fuel 211 to be supplied (from one or more pressure vessels 110) can be adjusted in a particularly precise manner.

[0068] The anode subsystem 500 can - as shown in Figure 5 - include a first pressure sensor 511, which is arranged to detect a first measured value of the (first) gas pressure on the input side of the fuel cell stack 102, in particular on the input side of the anode space of the fuel cell stack 102, for example on the anode inlet line 401. In addition, the anode subsystem 500 can include a second pressure sensor 512, which is arranged to detect a second measured value of the (second) gas pressure on the output side of the fuel cell stack 102, in particular on the output side of the anode space of the fuel cell stack 102, for example on the anode exhaust line 404. The second pressure sensor 512 can be arranged, for example - as shown in Figure 5 - downstream of the water separator 503 (so that the second pressure sensor 512 and / or the sensor data of the second pressure sensor 512 are not affected by the liquid water 506 in the anode exhaust line 404). Here, a positioning directly in the vicinity of the water separator 503 and / or the purge valve 507 is advantageous. In this way, the gas pressure on the output side of the fuel cell stack 102 can be determined in a particularly precise manner.

[0069] The fuel cell system 100 described herein includes a concentration sensor for determining the fuel concentration within the anode 201 or within the anode subsystem 500. In order to avoid insufficient fuel supply and thus increased aging or damage on the fuel cell stack 102, the anode 201 can be operated at an increased fuel concentration, which, however, results in a reduced energy efficiency of the fuel cell system 100.

[0070] Insufficient fuel supply can in particular be caused by the (possibly localized) accumulation of liquid water 506 in the anode 201. Such an accumulation of liquid water is typically difficult to measure or identify via an operating model because the generation or accumulation of liquid water 506 in the anode 201 is related to a variety of different factors (such as, for example, the purge strategy (for draining the anode 201), the stack operating temperature, the component temperature, the temperature gradient, the vehicle tilt, the operating point of the fuel cell stack 102, the operating history, the anode density, the anode pressure, the cathode pressure, the cathode air humidity, the vehicle vibration, the vehicle acceleration, etc.).

[0071] Due to the various influences on the liquid water budget (Flüssigwasserhaushalt) of the anode 201, the current anode state can mostly not be reliably determined by the sensor data of the sensors and / or via a model at different operating points of the fuel cell stack 102. The accumulation of liquid water 506 in the anode 201 can, depending on the operating state of the fuel cell stack 102, lead to: The fuel cell stack 102 reaches a critical state with respect to the accumulation of liquid water 506 within a period ranging from approximately 10 seconds (in cold operation and / or at full load) to approximately 10 minutes (in hot operation and / or at base load) based on the normal state (without significant accumulation of liquid water 506). In the critical state, there is local insufficient fuel supply in the anode 201, which leads to a reduction in the efficiency of the fuel cell stack 102 and / or an increase in the aging of the fuel cell stack 102. If the insufficient fuel supply is not recognized, this can lead to damage at the fuel cell stack 102. Therefore, an immediate and complete shutdown of the fuel cell system 100 can be achieved in response to a suspected supply shortage, but this reduces the availability of the fuel cell system 100.

[0072] In this document, the following measures are described by which the liquid water budget in the anode 201 of the fuel cell stack 102 can be monitored in an efficient, precise, and reliable manner. This also enables: An efficient and reliable operation of the fuel cell stack 102, in particular with respect to the fuel concentration in the anode 201 of the fuel cell stack 102.

[0073] Figure 6aShows the time curve of the pressure 610 on the anode inlet line 401 or on the anode exhaust line 404. The time curve of the pressure 610 can be detected by one or more pressure sensors 511, 512 of the anode subsystem 500. In order to remove the liquid water 506 from the anode 201 of the fuel cell stack 102 and / or from the collection container 505 of the anode subsystem 500, the anode purge valve 507 can be repeatedly opened to cause a so-called purge or flushing event. The (control) device 103 can be set to cause a (pulse-shaped) control signal 601 for controlling the anode purge valve 507 to open the anode purge valve 507 and thereby cause a purge event. Here, the duration of the purge event can be adjusted by the duration or width 605 of the pulsed control signal 601.

[0074] The anode purge valve 507 is opened by the control signal 601. Here, the opening degree of the anode purge valve 507 is typically shown by the current 602 that flows through the anode purge valve 507. From the current 602, it can thus be read how wide and / or for how long the anode purge valve 507 is effectively opened in the case of a purge event.

[0075] The opening of the anode purge valve 507 in the scope of the purge event causes: First, the liquid water 506 (from the collection container 505) to flow out. Therefore, the pressure 610 on the anode inlet line 401 and / or on the anode exhaust line 404 remains unchanged. This is visible in the case of the first purge event, which is shown on the Figure 6a left side. The purge event - in which basically only the liquid water 506 is removed from the anode subsystem 500 - can be called the first type of purge event. This phase of the purge event - in which basically only the liquid water 506 is removed from the anode subsystem 500 - can be called the first phase 611.

[0076] After most of the liquid water 506 has flowed out, more and more gas (especially the fuel 211) is mixed with the mass flow passing through the anode purge valve 507. The outflow of gas from the anode 201 causes the pressure 610 on the anode inlet line 401 and / or on the anode exhaust line 404 to drop. This is visible in the Figure 6b second purge event shown in the middle. The purge event - in which at least in the second phase 612 of the purge event the liquid water 506 together with gas is removed from the anode subsystem 500 - can be called the second type of purge event. The second phase 612 of the purge event has a determined duration 615 in the Figure 6a example shown.

[0077] In the third stage 613 of the purge event, the following can occur, namely that essentially only gas still flows through the anode purge valve 507. The third stage 613 can be identified by a significant drop in the gas pressure 610 in the anode inlet line 401 and / or in the anode exhaust line 404 (as can be seen, for example, in the purge event shown on the Figure 6a right side of Figure 6a ). Such a purge event can be referred to as a third type of purge event. Such a purge event thus includes a second stage 612 with a determined duration 615 and a subsequent third stage 613 with a determined duration 616.

[0078] In order to identify the type of purge event and / or in order to identify the stages 611, 612, 613 of the purge event, the measured pressure 610 can be compared with one or more pressure thresholds 621, 622. For example, it can be determined that if the pressure 610 drops below a first pressure threshold 621, then the purge event enters the second stage 612. Furthermore, it can be determined that if the pressure 610 drops below a second pressure threshold 622 (which is less than the first pressure threshold 621), then the purge event enters the third stage 613.

[0079] The (control) device 103 of the fuel cell system 100 can be set to repeatedly cause purge events. Furthermore, the individual purge events can be analyzed. In particular, the type of each purge event can be determined. Furthermore, the duration 615, 616 of one or more stages 611, 612, 613 of each purge event can be determined. Thus, one or more characteristics of one or more previous purge events can be determined. Then, the fuel cell system 100 can be operated based on the one or more characteristics of the one or more previous purge events determined. Herein, in particular, one or more operating parameters regarding the implementation of one or more subsequent purge events can be determined based on the one or more characteristics of the one or more previous purge events determined. Exemplary operating parameters are the duration 605 of the control signal 601 for a subsequent purge event and / or the repetition rate of the subsequent purge event or the time interval between two consecutive subsequent purge events.

[0080] One or more of the following rules can be applied in the determination of one or more operating parameters:

[0081] - If each of the one or more previous purge events has only the first stage 611 (and thus it cannot be ensured that the liquid water 506 is completely removed from the anode subsystem 500), then increase the duration 605 of the control signal 601 and / or decrease the time interval of the purge event (i.e., the control signal 601); and / or

[0082] - If each of the one or more previous purge events has already had a third phase 613 (and thus has also removed fuel 211 from the anode subsystem 500 in addition to liquid water 506, because it was "purged" too strongly), then reduce the duration 605 of the control signal 601 and / or increase the time interval of the purge event (i.e., the control signal 601).

[0083] It should be noted that additional rules can be applied to determine one or more operating parameters for one or more subsequent purge events. Generally, the adjustment of one or more operating parameters for subsequent purge events can be implemented based on the characteristics of past purge events. The adjustment can be directed at: reducing the duration 615, 616 of the second and / or third phases 612, 613 of the purge event (in particular, each reduced to zero) or setting to a rated value. In this way, the accumulation of liquid water 506 in the anode 201 can be prevented in an efficient and reliable manner.

[0084] Figure 6b An exemplary time curve of the purge event 631 is shown. In addition, Figure 6b It is clarified whether the fuel cell stack 102 is operating in an optimized state 640 (without significant accumulation of liquid water 506 and without significant loss of fuel 211 through the anode purge valve 507), in an inefficient state 641 (without significant accumulation of liquid water 506 but with significant loss of fuel 211 through the anode purge valve 507) or in a critical state 642 (with significant accumulation of liquid water 506 but without significant loss of fuel 211 through the anode purge valve 507) at the corresponding moment.

[0085] As can be seen from the time curve of the state 645 of the fuel cell stack 102, the adjustment of one or more operating parameters of the purge event 631 described herein contributes to setting the state of the fuel cell stack 102 close to the optimized state 640.

[0086] Thus, in the case of each purging event, the purging characteristics can be analyzed in real time on the control device 103 and classified into different stages 611, 612, 613. An assessment for achieving the critical state 642 of the fuel cell stack 102 can be derived based on the durations 615, 616 of the identified stages 611, 612, 613 and / or based on the accumulated results of previous purging events. Based on this assessment, one or more corresponding measures (such as, for example, increasing the purging rate, increasing the pressure (in the anode 201), reducing the current generated by the fuel cell stack 102, etc.) can be introduced in a timely manner before reaching the critical state 642, thereby increasing the system stability and / or the lifetime of the fuel cell stack 102. Alternatively or additionally, the supply of fuel 211 in the fuel cell stack 102 can be reduced (especially the "safety buffer"), thereby increasing the efficiency and / or the range of the fuel cell system 100.

[0087] The occurrence of purging events can be monitored continuously. Once a purging event occurs, the current 602 through the purge valve 507 can be used to determine the opening degree (since typically the opening degree is proportional to the current in the case of solenoid valves). Once the purge valve current 602 exceeds the current threshold (i.e., exceeds the minimum current for opening the valve 507), the first stage 611 begins, in which the discharge of liquid water is realized. In this first stage 611, only water 506 is discharged from the water separator 503 into the exhaust. The duration of the first stage 611 is initially related to the water level in the water separator 503 and / or to the pressure difference across the purge valve 507. Here, the pressure difference typically corresponds to the anode pressure relative to the ambient pressure.

[0088] Once a significant pressure drop 610 is detected (in the anode inlet 401 and / or in the anode outlet 404), the purging event is in the dynamic transition stage 612 (i.e., in the second stage). The second stage 612 is the transition from liquid water discharge to gas discharge. Here, typically no accurate description can be given for the corresponding part - liquid or gaseous. This transition is typically realized dynamically without a clearly definable separation of the stage parts (liquid or gaseous). Here, the proportion of the stage parts typically moves continuously from liquid water discharge to gas discharge. It can be observed that this dynamic transition (i.e., the second stage 612) has a substantially constant and / or the same duration 615 for different purging events (if the corresponding purging event is not interrupted prematurely).

[0089] Once the transition stage 612 ends, no significant liquid water part is discharged anymore. Then, (pure) gas discharge is realized in the third stage 613. In this third stage 613, there can still be water 506 in the water separator 503, but there is no longer sufficient pressure acting on the water 506 to discharge the water 506.

[0090] The anode state can be evaluated as follows, i.e., whether there is a second stage 612 or a third stage 613 during the purge event and how long each of these stages 612, 613 lasts if necessary. If a critical anode state 642 is recognized, the anode state can be influenced by one or more weighted corresponding measures (increasing the purge rate, increasing the pressure, reducing the current, etc.). If the anode state is in the inefficient range 641, one or more corresponding measures can be reduced. In addition, one or more measures for saving fuel 211 can be carried out. Thereby, the anode 201 can be kept in a range near the optimized state 640.

[0091] During dynamic vehicle operation, external (dynamic) influences can act on the pressure drop during the purge event (e.g., based on the driving operation of the motor vehicle). If an external influence is recognized, the following can be achieved through the above weighting, i.e., the purge event is evaluated earlier than critical (e.g., earlier than a purge event of the first type). Thereby, the evaluation may briefly move away from the optimized state 640 in the direction of the inefficient range 641. However, more serious damage mechanisms are thereby avoided. Medium-term, possible faults are compensated by the weighting of the evaluation (since external events during the purge event 631 are quite rare).

[0092] As Figure 6a shown, the time curve of the pressure 610 has a typical curve for the first, second, or third type of purge event 631. In particular, a stepwise decrease in the pressure 610 occurs during the second stage 612 and / or during the third stage 613 of the purge event 631. On the other hand, a stepwise increase in the pressure 610 occurs at the end of the purge event 631. The pressure 610 basically rises again to the same pressure value as before the start of the purge event 631 after the end of the purge event 631. Therefore, one or more reference curves can be determined and saved for the time curve of the pressure during the purge event 631 (e.g., respective reference curves for the first, second, and / or third type of purge event 631).

[0093] The device 103 can be set to check whether an external (dynamic) event has acted on the fuel cell system 100 during a purge event 631 (e.g., during the driving operation of a motor vehicle in which the fuel cell system 100 is installed). For this purpose, the sensor data of the motor vehicle (such as an acceleration sensor and / or an inertial measurement unit, for example) can be analyzed and processed. Alternatively or additionally, the device 103 can be set to check whether the time curve of the pressure 610 determined for the purge event 631 corresponds to a reference curve. If the time curve of the pressure 610 differs from one or more reference curves, it can be inferred that an external event has acted on the fuel cell system 100 during the purge event 631, and thus the time curve of the pressure 610 is distorted. Therefore, the classification can be carried out as to whether the time curve of the pressure 610 is undistorted (and thus can be used to adapt the operation of the fuel cell system 100) or distorted (and thus cannot or can only be used to a limited extent to adapt the operation of the fuel cell system 100).

[0094] The device 103 can be set, for example, to generally classify the purge event 631 as a first type of purge event if it is recognized that the time curve of the pressure 610 determined for the purge event 631 (based on an external event) is distorted. This can cause a particularly reliable and / or safe operation of the fuel cell system 100 (even when the fuel cell system 100 is used in a motor vehicle).

[0095] Figure 7 A flowchart showing a (possibly computer-implemented) method 700 for operating a fuel cell system 100 is shown, wherein the fuel cell system 100 has a fuel cell stack 102 and an anode subsystem 500 for receiving the fuel 211 of the fuel cell stack 102.

[0096] The method 700 includes determining 701 the time curve of the pressure 610 in the anode subsystem 500 (in particular in the anode inlet line 401 and / or in the anode exhaust line 404) during at least one previous purge event 631, wherein the purge event 631 aims to discharge the liquid water 506 from the anode subsystem 500, in particular from the water separator 503.

[0097] The method 700 further includes determining 702 one or more operating parameters for operating the fuel cell system 100 based on the detected time curve of the pressure 610.

[0098] The measures described herein can cause a particularly efficient and reliable operation of the fuel cell stack 102, especially with respect to the adjustment of an optimized anode state 640.

[0099] The present invention is not limited to the illustrated embodiments. In particular, it should be noted that the description and the drawings are only to illustrate the principles of the proposed methods, devices, and systems in an exemplary manner.

[0100] List of reference numerals

[0101] 100 Fuel cell system

[0102] 101 Fuel cell

[0103] 102 Fuel cell stack

[0104] 103 (Control) device

[0105] 110 Pressure vessel

[0106] 112 Fuel line

[0107] 201 Anode

[0108] 202 Cathode

[0109] 203 Separator

[0110] 204 Contact (electrode)

[0111] 205 Oxidant transporter

[0112] 211 Fuel (especially hydrogen)

[0113] 212 Oxidant (especially air)

[0114] 301 End plate

[0115] 302 Pipeline

[0116] 303 Bipolar plate

[0117] 304 Electrode-membrane unit

[0118] 401 Fuel input pipeline

[0119] 402 Oxidant input pipeline

[0120] 403 Reaction product outlet pipeline

[0121] 404 Anode exhaust pipeline

[0122] 500 Anode subsystem

[0123] 502 Recirculation pipeline

[0124] 503 Water separator

[0125] 504 Fuel recirculation transporter

[0126] 505 Collection container

[0127] 506 Water

[0128] 507 Valve

[0129] 511 Pressure Sensor (before the anode space of the fuel cell stack)

[0130] 512 Pressure Sensor (after the anode space of the fuel cell stack)

[0131] 601 (Pulsed) Control Signal

[0132] 602 Control Current

[0133] 605 Duration of the Control Current

[0134] 610 Pressure

[0135] 611, 612, 613 Phases of the Purge Event

[0136] 615, 616 Durations of the Phases

[0137] 621, 622 Pressure Thresholds

[0138] 631 Purge Event

[0139] 640 Optimized Anode State

[0140] 641 Inefficient Anode State

[0141] 642 Critical Anode State

[0142] 645 Actual Anode State

[0143] 700 Method for Operating a Fuel Cell Stack

[0144] 701 - 702 Method Steps

Claims

1. Apparatus (103) for operating a fuel cell system (100); wherein, the fuel cell system (100) has a fuel cell stack (102) and an anode subsystem (500) for receiving fuel (211) of the fuel cell stack (102); the apparatus (103) is arranged to, - determine a time curve of the pressure (610) in the anode subsystem (500) during at least one prior purge event (631) for discharging liquid water (506) from the anode subsystem (500); and - determine one or more operating parameters for operating the fuel cell system (100) based on the detected time curve of the pressure (610), the one or more operating parameters for operating the fuel cell system (100) including one or more operating parameters regarding the implementation of one or more subsequent purge events (631).

2. The apparatus (103) according to claim 1, wherein, the apparatus (103) is arranged to, - determine based on the time curve of the pressure (610): whether the prior purge event (631) includes at least one stage (612, 613) in which fuel (211) is discharged from the anode subsystem (500); and - determine the one or more operating parameters for operating the fuel cell system (100) based on whether the prior purge event (631) includes at least one stage (612, 613) in which fuel (211) is discharged from the anode subsystem (500).

3. The apparatus (103) according to any one of the preceding claims, wherein, the apparatus (103) is arranged to, - compare the time curve of the pressure (610) with at least one pressure threshold (621, 622); and - determine the one or more operating parameters for operating the fuel cell system (100) based on the comparison.

4. The apparatus (103) according to claim 3, wherein, the apparatus (103) is arranged to, - compare the time curve of the pressure (610) with a first pressure threshold (621) in order to —— determine: whether the prior purge event (631) includes a second stage (612) in which in addition to water (507) fuel (211) is also discharged from the anode subsystem (500), and / or —— determine the duration (615) of the second stage (612); and / or - compare the time curve of the pressure (610) with a second pressure threshold (622) in order to —— determine: whether the prior purge event (631) includes a third stage (613) in which substantially only fuel (211) is discharged from the anode subsystem (500), and / or —— determine the duration (616) of the third stage (613); wherein the second pressure threshold (622) is less than the first pressure threshold (621); and —— based on the fact that the prior purge event (631) includes the second stage (612) and / or the third stage (613); and / or ——based on the duration (615, 616) of the second stage and / or the third stage (612, 613) - to determine the one or more operating parameters for operating the fuel cell system (100).

5. The device (103) according to one of the preceding claims, wherein, the device (103) is configured to, - determine one or more characteristics of the previous purge event (631) based on the time curve of the pressure (610); the one or more characteristics particularly include: —— the fact that the previous purge event (631) only includes the first stage (611), in which only water (507) is discharged from the anode subsystem (500) substantially; —— the fact that the previous purge event (631) includes the second stage (612) in addition to the first stage (611), in which in addition to water (507), fuel (211) is also discharged from the anode subsystem (500); —— the fact that the previous purge event (631) includes the third stage (613) in addition to the second stage (612), in which substantially only fuel (211) is discharged from the anode subsystem (500); and / or —— the duration (615, 616) of the first stage, the second stage and / or the third stage (611, 612, 613); and - determine the one or more operating parameters for operating the fuel cell system (100) based on the one or more characteristics of the previous purge event (631).

6. The device (103) according to one of the preceding claims, wherein, the device (103) is configured to determine the one or more operating parameters for operating the fuel cell system (100) so as to cause: the duration (615, 616) of the stage (612, 613) of at least one subsequent purge event (631) in which fuel (211) is discharged from the anode subsystem (500) has a rated value.

7. The device (103) according to one of the preceding claims, wherein, the one or more operating parameters of the fuel cell system (100) include: - the duration (605) of at least one subsequent purge event (631); and / or - the time interval between the subsequent purge event (631) and the previous purge event (631); and / or - the repetition rate of the subsequent purge event (631); and / or - the opening degree of the purge valve (507) during the subsequent purge event (631); and / or - the value of the pressure (610) in the anode subsystem (500); and / or - the value of the electrical power of the fuel cell stack (102).

8. The device (103) according to claim 7, referring back to claim 5, wherein, the device (103) is configured to, - If the previous purge event (631) only includes the first stage (611), then increase the duration (605) and / or repetition rate of one or more subsequent purge events (631) and / or decrease the time interval of one or more subsequent purge events (631); and / or - If the previous purge event (631) includes the third stage (613), then decrease the duration (605) and / or repetition rate of one or more subsequent purge events (631) and / or increase the time interval of one or more subsequent purge events (631).

9. The device (103) according to one of the preceding claims, wherein, - The anode subsystem (500) includes a water separator (503) configured to separate liquid water (507) from the anode exhaust of the fuel cell stack (102); - The anode subsystem (500) includes a purge valve (507) configured to discharge the water (507) separated by the water separator (503) from the anode subsystem (500); and - The device (103) is configured to open the purge valve (507) to initiate a purge event (631).

10. The device (103) according to claim 9, wherein, The anode subsystem (500) is configured to, - If the purge event (631) has a total duration exceeding the duration of the first stage (611), then after the first stage (611) in which water (507) is substantially only discharged from the anode subsystem (500) during the purge event (631), fuel (211) is discharged from the anode subsystem (500) in at least one subsequent stage (612, 613); and / or - During the stage (612, 613) of the purge event (631) in which fuel (211) is discharged from the anode subsystem (500), the pressure (610) of the fuel (211) in the anode input line (401) to the anode (201) of the fuel cell stack (102) and / or the pressure (610) of the anode exhaust in the anode exhaust line (404) from the anode (201) decreases.

11. The device (103) according to one of the preceding claims, wherein, - The anode subsystem (500) includes at least one pressure sensor (511, 512) configured to detect the pressure (610) of the fuel (211) in the anode input line (401) to the anode (201) of the fuel cell stack (102) and / or the pressure (610) of the anode exhaust in the anode exhaust line (404) from the anode (201); and - The device (103) is configured to obtain the time curve of the pressure (610) in the anode subsystem (500) during the previous purge event (631) based on the sensor data of the pressure sensor (511, 512).

12. The device (103) according to one of the preceding claims, wherein, The device (103) is configured to, - Check: whether the time curve of the pressure (610) detected for the previous purge event (631), in particular based on an external dynamic event, is distorted; and - When determining the one or more operating parameters for operating the fuel cell system (100), consider the time curve of the detected pressure (610) depending on whether the time curve of the detected pressure (610) is recognized as being distorted.

13. The device (103) according to claim 2, referring back to claim 12, wherein, the device (103) is configured such that if it is recognized that the time curve of the pressure (610) detected for the previous purge event (631) is distorted, then determine that: the previous purge event (631) does not have a stage (612, 613) in which fuel (211) is discharged from the anode subsystem (500).

14. A method (700) for operating a fuel cell system (100); wherein, the fuel cell system (100) has a fuel cell stack (102) and an anode subsystem (500) for receiving the fuel (211) of the fuel cell stack (102); the method (700) includes: - During at least one previous purge event (631) for discharging liquid water (506) from the anode subsystem (500), determine (701) the time curve of the pressure (610) in the anode subsystem (500); and - Determine (702) one or more operating parameters for operating the fuel cell system (100) based on the time curve of the detected pressure (610), the one or more operating parameters for operating the fuel cell system (100) including one or more operating parameters regarding the implementation of one or more subsequent purge events (631).

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