Method and control device for monitoring a fuel cell system for hydrogen leakage and fuel cell system

Abstract

The invention relates to a method for monitoring a fuel cell system (100) for hydrogen leakage. The method comprises a step of detecting a hydrogen supply to an anode (A) of the fuel cell system (100), which hydrogen supply is shut off by at least one hydrogen metering valve (124) of the fuel cell system (100). The method further comprises a step of reading in a pressure sensor signal (S_p) via an interface (151) from a pressure detection device (116) of the fuel cell system (100). The pressure sensor signal (S_p) represents anode pressure values which indicate an actual pressure drop in the anode (A) or from which the actual pressure drop in the anode (A) can be determined. In addition, the method comprises a step of carrying out a comparison between the pressure sensor signal (S_p) and a specific reference value in order to generate comparison data. The method also comprises a step of checking the comparison data for fulfillment of a predefined leakage criterion indicating hydrogen leakage in order to determine a monitoring result (159).

Description

[0001] Description

[0002] title

[0003] Method and control unit for monitoring a fuel cell system for hydrogen leakage and fuel cell system

[0004] State of the art

[0005] The present invention relates to a method for monitoring a fuel cell system for hydrogen leakage, a corresponding control unit, a fuel cell system and a corresponding computer program product.

[0006] In a fuel cell or fuel cell system, electrical energy can be generated from hydrogen and oxygen. A leak from the anode of the fuel cell can conventionally be detected using two hydrogen concentration sensors, or H2 sensors. One H2 sensor can be placed, for example, at the top of a housing that encloses the fuel cell stack. This detects hydrogen that is unintentionally escaping the system. The second H2 sensor can be placed in the exhaust duct and detect whether an excessive amount of hydrogen is leaving the system through the exhaust duct. This can occur, for example, if the purge valve and / or drain valve no longer close tightly or if a leak in the stack allows hydrogen to flow onto the cathode side.

[0007] Disclosure of the invention

[0008] Against this background, the approach presented here introduces a method, a control unit that uses this method, a fuel cell system, and finally a corresponding computer program product according to the main claims. Advantageous embodiments are described in the respective dependent claims and the following description.

[0009] According to embodiments, a means of diagnosing anode leakage, or in other words, monitoring for hydrogen leakage, can be provided for a fuel cell system, eliminating the need for a second hydrogen sensor in the system. Thus, for example, leaks in a purge valve and / or a drain valve of the fuel cell system can be reliably detected without having to place a hydrogen sensor in an exhaust line of the fuel cell system. Therefore, not only can a hydrogen sensor installed in the exhaust line of the fuel cell system be dispensed with, but a stuck or leaking purge valve and / or drain valve can also be detected easily, quickly, and reliably during a phase with the hydrogen metering valve closed.

[0010] A method for monitoring a fuel cell system for hydrogen leakage is presented, the method comprising the following steps:

[0011] Detecting a hydrogen supply to an anode of the fuel cell system that is blocked by at least one hydrogen metering valve of the fuel cell system;

[0012] Reading a pressure sensor signal via an interface from a pressure sensing device of the fuel cell system, wherein the pressure sensor signal represents anode pressure values ​​that indicate an actual pressure drop in the anode or from which the actual pressure drop in the anode can be determined;

[0013] Performing a comparison between the pressure sensor signal and a specific reference value to generate comparison data; and

[0014] Checking the comparison data for compliance with a predefined leakage criterion indicating hydrogen leakage in order to determine a monitoring result. The fuel cell system may be intended for use in a vehicle, such as a passenger car or the like. The fuel cell system may, for example, be a PEM fuel cell system (PEM = Proton Exchange Membrane;

[0015] The fuel cell system can be a proton exchange membrane (PEM) fuel cell system, a polymer electrolyte (PEM) fuel cell system, or another type of fuel cell system. The fuel cell system can comprise multiple fuel cell modules, also known as a stack or fuel cell stack. Such fuel cell stacks can include many individual fuel cell modules or cells, which may be stacked and held together, for example, by a clamping system. Each individual cell may include a membrane that separates the media on the anode and cathode sides. A hydrogen metering valve may also be called an HGI (hydrogen gas injector).

[0016] Optionally, during the input step, a current signal can be read via an interface from a voltage sensing device of the fuel cell system. This current signal can represent an electric current currently generated by the fuel cell system. The procedure can also include a step for determining the reference value as an expected pressure drop in the anode using the current signal and a defined procedure. This procedure can define physicochemical relationships between the currently generated electric current and the expected hydrogen consumption, as well as between the expected hydrogen consumption and the expected pressure drop. Furthermore, during the execution step, a comparison can be made between the actual pressure drop and the expected pressure drop.The determination procedure used in the determination step can include a mass balance model in the anode. Such an embodiment offers the advantage of enabling particularly reliable and accurate leak detection. According to one embodiment, a limit value for a pressure drop gradient can be used as a leakage criterion in the verification step. Such an embodiment offers the advantage that a leak can be reliably detected if, for example, the gradient is greater than the limit value, i.e., if the pressure drop is greater than expected.

[0017] In the verification step, a limit value for the time period until a predefined threshold is reached or fallen below can also be used as a leakage criterion. This embodiment offers the advantage that a leak can be detected simply and reliably if, for example, the threshold is reached or fallen below faster than expected.

[0018] Furthermore, the method can include a step of closing the hydrogen metering valve to shut off the hydrogen supply. This closing step can be performed before the detection step. Such an embodiment offers the advantage that monitoring can also be carried out when needed, even if the hydrogen metering valve is not already closed, such as during dynamic load changes or pulsed anode operation. Additionally, the method can include a step of releasing the hydrogen metering valve to restore an operationally induced adjustment of the hydrogen supply when the monitoring step is complete or at least one of the anode pressure values ​​reaches or falls below a predefined threshold.Such an embodiment offers the advantage that safe operation of the fuel cell system can be maintained even if the hydrogen metering valve has been actively closed for monitoring purposes.

[0019] The approach presented here further creates a control unit that is configured to carry out or implement the steps of a variant of the method presented here in appropriate facilities. This embodiment of the invention in the form of a control unit also allows the problem underlying the invention to be solved quickly and efficiently.

[0020] The control unit can be designed as a fuel cell control unit of the fuel cell system or as a part of such a fuel cell control unit. Alternatively, the control unit can be connected to a fuel cell control unit of the fuel cell system via a signal transmission device.

[0021] In this context, a control unit can be understood as an electrical device that processes sensor signals and outputs control and / or data signals accordingly. The control unit can have an interface, which can be implemented in hardware and / or software. In the case of a hardware-based interface, the interfaces can, for example, be part of a so-called system ASIC, which incorporates various functions of the control unit. However, it is also possible that the interfaces are separate integrated circuits or at least partially comprised of discrete components. In the case of a software-based interface, the interfaces can be software modules, which, for example, are located on a microcontroller alongside other software modules.

[0022] A fuel cell system is also presented, which has the following features:

[0023] a pressure sensing device configured to provide a pressure sensor signal representing anode pressure values ​​indicating an actual pressure drop in an anode of the fuel cell system, or from which the actual pressure drop in the anode can be determined;

[0024] at least one hydrogen metering valve configured to regulate the hydrogen supply to an anode of the fuel cell system; and

[0025] an embodiment of a control unit mentioned herein, wherein the control unit is connected to the pressure sensing device and the at least one hydrogen metering valve in a signal-transmitting manner.

[0026] In conjunction with the fuel cell system, an embodiment of the control unit mentioned herein can thus be advantageously employed or used to monitor the fuel cell system for hydrogen leakage. Optionally, the fuel cell system can additionally include a voltage sensing device configured to provide a current signal representing an electrical current currently generated by the fuel cell system. The control unit can be connected to the voltage sensing device via a signal transmission mechanism.

[0027] According to one embodiment, the fuel cell system can have a single hydrogen detection device for measuring the hydrogen concentration. This hydrogen detection device can be arranged on a stack housing of the fuel cell system. Such an embodiment offers the advantage that a leak at this point can be detected quickly and reliably.

[0028] It is also advantageous to have a computer program product with program code that can be stored on a machine-readable medium such as semiconductor memory, hard disk memory or optical memory and is used to carry out the method according to one of the embodiments described above, if the program product is executed on a computer or device.

[0029] The approach presented here is explained in more detail below using the attached drawings as examples. These show:

[0030] Fig. 1 shows a schematic representation of an embodiment of a fuel cell system; and

[0031] Fig. 2 shows a flowchart of an embodiment of a method for monitoring a fuel cell system for hydrogen leakage.

[0032] In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and acting similarly, without repeating these elements.

[0033] Fig. 1 shows a schematic representation of an embodiment of a fuel cell system 100. The fuel cell system 100 is designed for automotive use or for use in a motor vehicle, or is arranged in a motor vehicle. The fuel cell system 100 is, for example, a PEM fuel cell system.

[0034] Proton exchange membrane fuel cell system (PEM = Proton Exchange Membrane).

[0035] According to the embodiment shown here, the fuel cell system 100 comprises a hydrogen subsystem, an air subsystem, and a fuel cell stack 110 consisting of many individual cells arranged in a stack housing 111, which can, for example, be stacked and held together by a clamping system. Each individual cell can have a membrane that separates the media on the anode side and the cathode side from each other.

[0036] The hydrogen subsystem shown in Fig. 1 includes, by way of example, a hydrogen supply line 121 from a tank (after pressure reduction), a system isolation valve 122, a heat exchanger 123, a hydrogen metering valve 124 designed to adjust the hydrogen supply to an anode A of the fuel cell system 100, a jet pump 125, a water separator 126, a drain valve 127 to the cathode path or air subsystem, a purge valve 128 to the cathode path or air subsystem, and a recirculation blower 129.

[0037] The air subsystem shown in Fig. 1 includes, by way of example, an air supply line 131 for ambient air, an air filter 132, a conveying unit 133 comprising an electric air compressor with turbine, an intercooler 134, a humidifier 135, a humidifier bypass valve 136, stack separator valves 137, a water separator 138, a Denk bypass valve 139, a pressure regulating valve 141, an inlet 142 from the anode path, more precisely from the drain valve 127 and the purge valve 128, a silencer 143 and an outlet line 144 for air and water.

[0038] The fuel cell stack 110 comprises the anode A (or stack anode) and a cathode K (or stack cathode). Furthermore, the fuel cell stack 110 includes electrical stack connections 112 and stack cooling connections 114. A number of sensors or detection devices are also associated with the fuel cell stack 110, of which only a pressure detection device 116, a voltage detection device 118, and a hydrogen detection device 119 are explicitly named here as examples. A temperature detection device may also be provided.

[0039] The pressure sensing device 116 is configured to provide a pressure sensor signal S_p representing anode pressure values ​​that indicate an actual pressure drop in the anode A of the fuel cell system 100 or from which the actual pressure drop in the anode A can be determined.

[0040] The voltage sensing device 118 is configured to provide a current signal S_l representing an electric current currently generated by the fuel cell system 100. The voltage sensing device 118 is, for example, a so-called Cell Voltage Monitor (CVM) or the like.

[0041] The hydrogen detection device 119 is the only hydrogen detection device of the fuel cell system 100. The hydrogen detection device 119 is designed to detect a hydrogen concentration. The hydrogen detection device 119 is arranged on the stack housing 111.

[0042] The fuel cell system 100 further comprises a control unit 150. The control unit 150 is designed to monitor the fuel cell system 100 for hydrogen leakage. The control unit 150 is connected to the pressure sensing device 116 and the at least one hydrogen metering valve 124 via signal transmission. Optionally, the control unit 150 is also connected to the voltage sensing device 118 via signal transmission.

[0043] The control unit 150 comprises a recognition device 153, a reading device 154, a processing device 156, and a verification device 157. The control unit 150 also includes an interface 151 or communication interface. Optionally, the control unit 150 may additionally include a locking device 152 and / or a determination device 155 and / or a release device 158. All components of the control unit 150 are interconnected to transmit signals.

[0044] The detection device 153 is configured to detect a hydrogen supply to the anode A that is shut off by the at least one hydrogen metering valve 124. The reading device 154 is configured to read the pressure sensor signal S_p from the pressure sensing device 116 via the interface 151. The feedthrough device 156 is configured to perform a comparison between the pressure sensor signal S_p and a specific reference value in order to generate comparison data. The verification device 157 is configured to check the comparison data for compliance with a predefined leakage criterion indicating hydrogen leakage in order to determine a monitoring result 159. The monitoring result 159 indicates whether or not a hydrogen leakage is present and optionally includes additional quantitative information about any hydrogen leakage.

[0045] According to one embodiment, the inspection device 157 is designed to use a limit value for a gradient of the pressure drop obtained from the pressure sensor signal S_p as a leakage criterion.

[0046] Additionally or alternatively, the inspection device 157 is designed to use as a leakage criterion a limit value for a time period until a predefined threshold is reached or fallen below by at least one of the anode pressure values ​​of the pressure sensor signal S_p.

[0047] According to a further embodiment, the reading device 154 is also configured to read the current signal S_l from the voltage sensing device 118 via the interface 151. In this embodiment, the optionally included determination device 155 is configured to determine the reference value for the feedthrough device 156 as an expected pressure drop in the anode A using the current signal S_l and a determination procedure. The determination procedure defines physicochemical relationships between the currently generated electric current and an expected hydrogen consumption dependent on the currently generated electric current, and between the expected hydrogen consumption and the expected pressure drop. Furthermore, the feedthrough device 156 is configured to perform the comparison between the actual pressure drop and the expected pressure drop.

[0048] According to one embodiment, the optional additional closing device 152 is designed to close the hydrogen metering valve 124 in order to shut off the hydrogen supply. The optional additional releasing device 158 is designed to release the hydrogen metering valve 124 to restore the hydrogen supply to an operationally determined setting when the monitoring device 157 has performed the check or at least one of the anode pressure values ​​of the pressure sensor signal S_p reaches or falls below a predefined threshold.

[0049] In other words, Fig. 1 shows, among other things, a structure of an anode system or hydrogen subsystem of the fuel cell or fuel cell system 100 with the hydrogen metering valve 124, the drain valve 127, and the purge valve 128, as well as a structure of a cathode system or air subsystem of the fuel cell or fuel cell system 100, where the inlet 142 marks the point where a purge / drain line is connected to the exhaust air line. Using the control unit 150, for example, a leaking purge valve and / or drain valve can be detected.

[0050] Fig. 2 shows a flowchart of an embodiment of method 250 for monitoring a fuel cell system for hydrogen leakage. The monitoring method 250 can be implemented to monitor the fuel cell system from Fig. 1 or a similar fuel cell system for hydrogen leakage. The monitoring method 250 can be implemented using the control unit from Fig. 1 or a similar control unit. The monitoring method 250 comprises a detection step 253, a reading step 254, an execution step 256, and a verification step 257.

[0051] In step 253 of the detection process, a hydrogen supply to an anode of the fuel cell system that is blocked by at least one hydrogen metering valve of the fuel cell system is detected. The subsequent steps of procedure 250 for monitoring are therefore only executed if the blocked hydrogen supply has been detected. Subsequently, in step 254 of the reading process, a pressure sensor signal is read via an interface from a pressure sensing device of the fuel cell system. The pressure sensor signal represents anode pressure values ​​that indicate an actual pressure drop in an anode of the fuel cell system or from which the actual pressure drop in the anode can be determined. Following this, in step 256 of the execution process, a comparison is made between the pressure sensor signal and a specific reference value to generate comparative data.

[0052] In step 257 of the verification process, the comparison data is subsequently checked for compliance with a predefined leakage criterion indicating hydrogen leakage in order to determine a monitoring result.

[0053] According to one embodiment, in step 254 of the reading process, a current signal is read via an interface from a voltage sensing device of the fuel cell system. The current signal represents an electric current currently generated by the fuel cell system. Here, the monitoring method 250 also includes step 255 of determining the reference value as an expected pressure drop in the anode using the current signal and a determination procedure. The determination procedure defines physicochemical relationships between the currently generated electric current and an expected hydrogen consumption dependent on the currently generated electric current, and between the expected hydrogen consumption and the expected pressure drop. Furthermore, in step 256 of the execution process, a comparison is made between the actual pressure drop and the expected pressure drop.

[0054] According to one embodiment, the monitoring method 250 also includes a step 252 of closing the hydrogen metering valve to shut off the hydrogen supply. The closing step 252 is performed before the detection step 253. Additionally, the monitoring method 250 also includes a step 258 of releasing the hydrogen metering valve to restore an operationally induced adjustment of the hydrogen supply when the checking step 257 is completed or at least one of the anode pressure values ​​reaches or falls below a predefined threshold.

[0055] With reference to the figures described above, exemplary embodiments and their advantages are summarized and explained in other words below.

[0056] In the event of leaks in the purge valve 128 and / or drain valve 127, an unacceptably large amount of hydrogen escapes the hydrogen subsystem or anode system. When the hydrogen metering valve 124 is closed, no hydrogen is added to the system. The consumed hydrogen can be accurately modeled using the stack flow rate. From this, the expected pressure drop in anode A can be determined. If hydrogen also flows out through a leaking purge valve 128 and / or drain valve 127, this leads to a greater pressure drop, which can be detected by the existing pressure sensor 116. An H₂ sensor in the exhaust line is not required.

[0057] For a low-tolerance model of the mass balance in anode A, it is necessary to close the hydrogen metering valve 124. This can be achieved in three different ways: (1) During dynamic load changes, the anode pressure regulator closes the hydrogen metering valve 124 to reduce the pressure in anode A. (2) During pulsed operation of anode A, the hydrogen metering valve 124 is opened and closed cyclically. (3) For testing or monitoring purposes, the hydrogen metering valve 124 is briefly closed by the closing device 152, specifically during step 252 of the closing process, to perform the diagnostics or monitoring described here.

[0058] With the hydrogen metering valve 124 closed, no hydrogen is added to the system. The hydrogen consumed in the reaction can be modeled with low tolerance using the stack flow rate. From this, the expected pressure drop in anode A can be determined. If hydrogen also flows out via a leaking purge valve 128 and / or drain valve 127, this leads to a greater pressure drop, which can be detected by the existing pressure sensor 116. If the hydrogen metering valve 124 was closed for testing purposes as mentioned above, the test should be terminated as soon as the pressure in anode A reaches a minimum threshold or the predefined threshold value. In this case, instead of the pressure gradient, the time until the minimum threshold is reached can also be used as a diagnostic or leakage criterion.

[0059] The embodiments described and shown in the figures are only examples. Different embodiments can be combined completely or with respect to individual features. An embodiment can also be supplemented by features from another embodiment.

[0060] Furthermore, the procedural steps presented here can be repeated and carried out in a different order than described.

[0061] If an embodiment includes an “and / or” connection between a first feature and a second feature, this is to be read as meaning that the embodiment according to one embodiment has both the first feature and the second feature, and according to another embodiment either only the first feature or only the second feature.

Claims

Claims 1. Method (250) for monitoring a fuel cell system (100) for hydrogen leakage, wherein the method (250) comprises the following steps: Detect (253) a hydrogen supply to an anode (A) of the fuel cell system (100) that is blocked by at least one hydrogen metering valve (124) of the fuel cell system (100); Reading (254) a pressure sensor signal (S_p) via an interface (151) from a pressure sensing device (116) of the fuel cell system (100), wherein the pressure sensor signal (S_p) represents anode pressure values ​​that indicate an actual pressure drop in the anode (A) or from which the actual pressure drop in the anode (A) can be determined; Performing (256) a comparison between the pressure sensor signal (S_p) and a specified reference value to generate comparison data; and Check (257) the comparison data for compliance with a predefined leakage criterion indicating hydrogen leakage in order to determine a monitoring result (159).

2. Method (250) according to claim 1, wherein in step (254) of reading, a current signal (S_l) is read via an interface (151) from a voltage sensing device (118) of the fuel cell system (100), wherein the current signal (S_l) represents an electric current currently generated by the fuel cell system (100), wherein the method (250) comprises a step (255) of determining the reference value as an expected pressure drop in the anode (A) using the current signal (S_l) and a determination procedure, wherein the determination procedure describes physicochemical relationships between the currently generated electric current and an expected value depending on the currently generated electric current. Hydrogen consumption and between the expected hydrogen consumption and the expected pressure drop are defined, wherein in step (256) of the execution the comparison between the actual pressure drop and the expected pressure drop is carried out.

3. Method (250) according to one of the preceding claims, wherein in step (257) of checking a limit value for a gradient of pressure drop is used as a leakage criterion.

4. Method (250) according to one of the preceding claims, wherein in step (257) of checking, a limit value for a time period until a predefined threshold is reached or fallen below is used as a leakage criterion by at least one of the anode pressure values.

5. Method (250) according to one of the preceding claims, comprising a step (252) of closing the hydrogen metering valve (124) to shut off the hydrogen supply, wherein the closing step (252) is performed before the detection step (253), and comprising a step (258) of releasing the hydrogen metering valve (124) to release an operational adjustment of the hydrogen supply when the checking step (257) is completed or at least one of the anode pressure values ​​reaches or falls below a predefined threshold.

6. Control unit configured to perform the steps (252, 253, 254, 255, 256, 257, 258) of a method (250) according to one of the preceding claims in corresponding devices (152, 153, 154, 155, 156, 157, 158).

7. Fuel cell system (100) having the following features: a pressure sensing device (116) configured to provide a pressure sensor signal (S_p) representing anode pressure values ​​that reflect an actual pressure drop in an anode (A) of the display fuel cell system (100) or from which the actual pressure drop in the anode (A) can be determined; at least one hydrogen metering valve (124) configured to regulate the hydrogen supply to an anode (A) of the fuel cell system (100); and a control unit (150) according to claim 6, wherein the control unit (150) is connected to the pressure sensing device (116) and the at least one hydrogen metering valve (124) in a signal-transmitting manner.

8. Fuel cell system (100) according to claim 7, comprising a single hydrogen detection device (119) for detecting a hydrogen concentration, wherein the hydrogen detection device (119) is arranged on a stack housing (111) of the fuel cell system (100).

9. Computer program configured to execute and / or control the steps of the method (250) according to any one of claims 1 to 5.

10. Machine-readable storage medium on which the computer program according to claim 9 is stored.

Images