Diagnostic method for diagnosing a state of a fuel cell-powered energy supply system

Abstract

The invention relates to a diagnostic method (100) for diagnosing a state of an energy supply system (200), which comprises a number of fuel cell systems (201, 203).

Description

[0001] Description

[0002] title

[0003] DIAGNOSTIC PROCEDURE FOR DIAGNOSIS OF A CONDITION OF A FUEL CELL-POWERED POWER SUPPLY SYSTEM

[0004] The presented invention relates to a diagnostic method for diagnosing a state of an energy supply system, an energy supply system, a vehicle and a program product according to the appended claims.

[0005] State of the art

[0006] Polymer electrolyte membrane (PEM) fuel cell systems convert hydrogen using oxygen to electrical energy, generating waste heat and water.

[0007] Converting hydrogen means that hydrogen molecules are consumed or removed on the anode side.

[0008] A PEM fuel cell consists of an anode supplied with hydrogen, a cathode supplied with air, and the polymer electrolyte membrane placed in between.

[0009] Several such individual fuel cells are stacked to form a fuel cell stack in order to increase the generated electrical voltage.

[0010] Within such a fuel cell stack, or “stack”, there are supply channels that supply the individual cells with hydrogen and

[0011] Supply air or remove the depleted humid air and the depleted anode exhaust gas. The supply of fresh hydrogen is carried out by hydrogen dosing valves, which can be designed as proportional valves.

[0012] The control strategy involves using a hydrogen dosing valve to regulate the gas pressure within an anode path, measured by a pressure sensor at a defined position, to a defined target pressure depending on the system operating point.

[0013] Reasons for the additional supply of fresh hydrogen can be, on the one hand, the consumption of hydrogen through electrochemical conversion and, on the other hand, other losses of gas molecules from the anode chamber, for example, due to a purge valve being opened for too long.

[0014] Depending on the hydrogen mass flow upstream of the hydrogen dosing valve, a pressure drop occurs relative to the high-pressure hydrogen regulator located further upstream.

[0015] Disclosure of the invention

[0016] Within the scope of the invention presented, a diagnostic method, an energy supply system, a vehicle, and a program product are presented. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details described in connection with the diagnostic method according to the invention naturally also apply in connection with the energy supply system according to the invention, the vehicle according to the invention, or the program product according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0017] The invention presented serves in particular to provide a robust fuel cell system.

[0018] Thus, according to a first aspect of the invention presented, a diagnostic method for diagnosing a state of an energy supply system comprising a number of fuel cell systems, ie one fuel cell system or several fuel cell systems, is presented.

[0019] The presented diagnostic method comprises measuring a supply pressure in a supply line between a number of high-pressure tanks and the number of fuel cell systems, in the flow direction after a high-pressure regulator and before respective shut-off valves of the number of fuel cell systems, measuring a specific pressure for each fuel cell system of the number of fuel cell systems in a consumer area after a shut-off valve for shutting off a hydrogen supply to a respective fuel cell system and before a metering valve for metering hydrogen into an anode subsystem of a respective fuel cell system, determining a specific mass flow for each fuel cell system of the number of fuel cell systems as a function of the supply pressure and a respective specific pressure, and outputting an error message in the eventthat at an identical operating point of respective fuel cell systems of the number of fuel cell systems, respective specific mass flows differ from each other by a diagnostic value that is greater than a predetermined threshold value.

[0020] The presented invention is based on the principle that a pressure curve in a medium pressure range, i.e., a range between a high pressure range in a tank system and a low pressure range in a fuel cell stack, is evaluated in order to determine a specific mass flow that is supplied to a respective fuel cell system.

[0021] Since the respective mass flows of the various fuel cell systems of an energy supply system should be comparable, in particular identical, at the same operating points of the various fuel cell systems, a deviation in the mass flows can be assumed to be a fault in one of the various fuel cell systems, in particular in the fuel cell system to which a larger mass flow is supplied. Accordingly, a corresponding error message can be output in such a case. It can be provided that the diagnostic method further comprises outputting the specific mass flows to at least one receiver function.

[0022] By outputting the specific mass flows to a receiver function in, for example, a vehicle or a control unit, the receiver function can be specifically adjusted to the state of the number of fuel cell systems.

[0023] It can further be provided that the supply pressure is measured in an area upstream of a distributor which distributes hydrogen flowing through the supply line to respective fuel cell systems of the number of fuel cell systems.

[0024] A supply pressure measured in an area upstream of a distributor that distributes hydrogen flowing through the supply line to the respective fuel cell systems of the number of fuel cell systems represents a reference that is the same for all fuel cell systems and that changes the same for all fuel cell systems. Accordingly, a supply pressure measured in an area upstream of a distributor that distributes hydrogen flowing through the supply line to the respective fuel cell systems of the number of fuel cell systems minimizes variance in determining the diagnostic value and maximizes the reliability of the proposed diagnostic method.

[0025] It may further be provided that when determining a respective specific mass flow, a specific hydraulic resistance in a respective consumer area is taken into account.

[0026] Considering a specific hydraulic resistance in a particular consumer zone requires the comparability of the respective specific mass pressures, even with different line geometries for the respective fuel cell systems. Furthermore, the respective specific hydraulic resistances can be determined through a flow simulation or by measuring with mass flow sensors integrated into or downstream of the respective consumer zones.

[0027] Specific hydraulic resistances can be determined once for a particular configuration of an energy supply system and then used as predefined values, e.g. as coefficients, to carry out the presented diagnostic procedure in the use of an energy supply system.

[0028] It can further be provided that, when determining a respective specific mass flow, a hydraulic resistance of the supply line is taken into account in addition to a specific hydraulic resistance in a respective consumer area.

[0029] Since the hydraulic resistance of the supply line also affects a mass flow in a respective consumer area, the hydraulic resistance of the supply line can also be determined in advance for a respective configuration of an energy supply system and then used as predetermined values, e.g. as coefficients, to carry out the presented diagnostic procedure in the use of an energy supply system.

[0030] According to a second aspect, the presented invention relates to an energy supply system for supplying a consumer with electrical energy.

[0031] The presented energy supply system comprises a tank system comprising a number of high-pressure tanks and a pressure reducer arranged in a central supply line, a number of fuel cell systems, each of which is fluidly connected to the supply line via a specific consumer line, a supply pressure sensor arranged in the supply line between the number of high-pressure tanks and the number of fuel cell systems, in the flow direction downstream of the high-pressure regulator and upstream of respective shut-off valves of the number of fuel cell systems, a plurality of specific pressure sensors arranged in a consumer area downstream of a shut-off valve for shutting off a hydrogen supply to a respective fuel cell system and upstream of a metering valve for metering hydrogen into an anode subsystem of a respective fuel cell system, and a computing unit configured toto carry out a possible design of the presented diagnostic procedure.,

[0032] The presented energy supply system is based on the use of a number of fuel cell systems, which are operated in parallel, for example, in order to maximize the performance of the energy supply system.

[0033] Accordingly, it can be provided that the energy supply system comprises a first fuel cell system and a second fuel cell system.

[0034] A configuration of the presented energy supply system with two fuel cell systems has proven particularly suitable for powering vehicles, as it represents a good compromise between performance and space requirements. Of course, the presented energy supply system is also conceivable with one or multiple fuel cell systems.

[0035] It can further be provided that the computing unit is a central server that is communicatively connected to a control unit of the energy supply system.

[0036] By using a central server as a processing unit, the server can monitor the status of a particular energy supply system, allowing, for example, repairs or maintenance of the energy supply system to be automatically scheduled if an error message is issued. A single server can serve as a processing unit for multiple energy supply systems.

[0037] According to a third aspect, the presented invention relates to a vehicle, wherein the vehicle comprises a possible embodiment of the presented energy supply system. According to a fourth aspect, the presented invention relates to a program product, wherein the program product comprises program code means that configure a computing unit to execute a possible embodiment of the presented diagnostic method when the program product is executed on the computing unit.

[0038] Advantages that are described in detail for the diagnostic method for diagnosing a state of an energy supply system according to the first aspect of the invention apply equally to the energy supply system for supplying a consumer with electrical energy according to the second aspect of the invention, to the vehicle according to the third aspect of the invention and to the program product according to the fourth aspect of the invention.

[0039] Further advantages, features, and details of the invention will become apparent from the following description, which describes exemplary embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0040] They show:

[0041] Figure 1 shows a possible design of the presented diagnostic procedure,

[0042] Figure 2 shows a schematic representation of a possible design of the presented energy supply system,

[0043] Figure 3 shows a possible design of the presented vehicle.

[0044] Figure 1 illustrates a diagnostic method 100 for diagnosing a condition of an energy supply system 200 according to Figure 2, which comprises a plurality of fuel cell systems 201 and 203. The diagnostic method 100 comprises a first measuring step 101, in which a supply pressure is measured in a supply line 205 between a number of high-pressure tanks 207 and the plurality of fuel cell systems 201, 203, downstream of a high-pressure regulator 209 and upstream of respective shut-off valves 211, 213 of the plurality of fuel cell systems 201, 203.

[0045] Furthermore, the diagnostic method 100 comprises a second measuring step 103 in which a specific pressure is measured for each fuel cell system 201, 203 in a consumer area 215, 217 after a shut-off valve 211, 213 for shutting off a hydrogen supply to a respective fuel cell system 201, 203 and before a metering valve 219, 221 for metering hydrogen into an anode subsystem of a respective fuel cell system 201, 203.

[0046] Furthermore, the diagnostic method 100 comprises a determination step 105 in which a specific mass flow is calculated for each fuel cell system 201, 203 as a function of the supply pressure and a respective specific pressure, for example according to formulas (1) to (4).

[0047] Furthermore, the diagnostic method 100 comprises an output step 107 in which an error message is output in the event that, at an identical operating point of the fuel cell systems 201, 203, respective specific mass flows differ from one another by a diagnostic value that is greater than a predetermined threshold value.

[0048] Figure 2 shows an energy supply system 200.

[0049] The energy supply system 200 comprises a first fuel cell system 201 and a second fuel cell system 203, as well as a supply line 205 between a number of high-pressure tanks 207 and the fuel cell systems 201, 203, a high-pressure regulator 209, and shut-off valves 211, 213, through which a mass flow of hydrogen to the fuel cell systems 201, 203 can be shut off. The first fuel cell system 201 is supplied with hydrogen by a first metering valve 219 arranged in a first consumer area 215, and the second fuel cell system 203 is supplied with hydrogen by a second metering valve 221 arranged in a second consumer area 217.

[0050] The points marked with P represent the respective pressures, and the points marked with R represent the respective resistances of the pipe geometries. Ro, Ri, R2, Po, Pi, and P2 are known, while P0', Vo, V1, and V2 are unknown. Accordingly, there are four unknowns for four equations, resulting in a solvable system.

[0051] After determining the volume flow, the density can be used to convert it into the mass flow.

[0052] The relationship shown can be stored in a data model in the computing unit provided according to the invention in order to easily determine the respective mass flows based on pressure measurements.

[0053] The following relationships apply to the calculations according to diagnostic procedure 100:

[0054] Pi = Po' - Pi ■ Vi (3)

[0055] P2=P o - - R2■ V2 2 (4)

[0056] For energy supply systems that have a specific pipe geometry, i.e., where, for example, pipes or pipe fittings differ between the respective fuel cell systems, this difference can be mathematically considered or compensated for by equations (5), (6) and (7). m = o ■ V (7)

[0057] Equation (5) applies to line geometries with pipes and equation (6) applies to line geometries with pipe fittings, which may include, for example, valves, heat exchangers and / or pipes.

[0058] The focus is for a resistance factor of pipe fittings such as heat exchangers, valves or pipes.

[0059] The resistance value of a pipe is determined using the term A ■ - D.

[0060] The relationships are outlined here as an example for a configuration with two fuel cell systems. The procedure can be applied analogously for n systems.

[0061] Figure 3 shows a vehicle 300. The vehicle 300 includes the energy supply system 200 shown in Figure 2.

Claims

Claims 1. Diagnostic method (100) for diagnosing a state of an energy supply system (200) comprising a number of fuel cell systems (201, 203), the diagnostic method (100) comprising: - measuring (101) a supply pressure in a supply line (205) between a number of high-pressure tanks (207) and the number of fuel cell systems (201, 203), in the flow direction after a high-pressure regulator (209) and before respective shut-off valves (211, 213) of the number of fuel cell systems (201, 203), - measuring (103) a specific pressure for each fuel cell system (201, 203) of the number of fuel cell systems (201, 203) in a respective consumer area (215, 217) after a shut-off valve (211, 213) for shutting off a hydrogen supply to a respective fuel cell system (201, 203) and before a metering valve (219, 221) for metering hydrogen into an anode subsystem of a respective fuel cell system (201, 203), - determining (105) a specific mass flow for each fuel cell system (201, 203) of the number of fuel cell systems (201, 203) as a function of the supply pressure and a respective specific pressure, - Outputting (107) an error message in the event that, at an identical operating point of respective fuel cell systems (201, 203) of the number of fuel cell systems (201, 203), respective specific mass flows differ from one another by a diagnostic value which is greater than a predetermined threshold value.

2. Diagnostic method (100) according to claim 1, characterized in that the diagnostic method further comprises: - Output of the specific mass flows to at least one receiver function.

3. Diagnostic method (100) according to claim 1 or 2, characterized in that the supply pressure is measured in a region upstream of a distributor which distributes hydrogen flowing through the supply line (205) to respective fuel cell systems (201, 203) of the number of fuel cell systems (201, 203).

4. Diagnostic method (100) according to one of the preceding claims, characterized in that when determining a respective specific mass flow, a specific hydraulic resistance in a respective consumer area (215, 217) is taken into account.

5. Diagnostic method (100) according to claim 4, characterized in that respective specific hydraulic resistances are determined by a flow simulation or by measuring with mass flow sensors integrated in respective consumer areas (215, 217) or connected downstream of the respective consumer areas (215, 217).

6. Diagnostic method (100) according to claim 4 or 5, characterized in that when determining a respective specific mass flow, a hydraulic resistance of the supply line (205) is taken into account in addition to a specific hydraulic resistance in a respective consumer area.

7. Energy supply system (200) for supplying a consumer with electrical energy, the energy supply system (200) comprising: a tank system comprising a number of high-pressure tanks (207) and a pressure reducer (209) arranged in a central supply line (205), a number of fuel cell systems (201, 203), each of which is fluidly connected to the supply line (205) via a specific consumer line, a supply pressure sensor arranged in the supply line (205) between the number of high-pressure tanks (207) and the number of fuel cell systems (201, 203), in the flow direction downstream of the high-pressure regulator (209) and upstream of respective shut-off valves (211, 213) of the number of fuel cell systems (201, 203), a plurality of specific pressure sensors arranged in a consumer area (215, 217) downstream of a shut-off valve (211, 213) for shutting off a hydrogen supply to a respective fuel cell system (201, 203) and upstream of a metering valve (219, 221) for metering hydrogen into an anode subsystem of a respective fuel cell system (201,203), a computing unit configured to carry out a diagnostic method (100) according to one of claims 1 to 5., 8. Energy supply system (200) according to claim 7, characterized in that the energy supply system (200) comprises a first fuel cell system (201) and a second fuel cell system (203).

9. Energy supply system (200) according to claim 7 or 8, characterized in that the computing unit is a central server which is communicatively connected to a control unit of the energy supply system (200).

10. Vehicle (300), wherein the vehicle (300) comprises a power supply system (200) according to claim 8 or 9. 11 . Program product, wherein the program product comprises program code means that configure a computing unit to execute a diagnostic method (100) according to one of claims 1 to 6 when the program product is executed on the computing unit.

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