Method for controlling an air compressor system with at least two air compressor units of a fuel cell system for a vehicle

Abstract

The disclosure comprises a method (100) for controlling an air compressor system (50) with at least two air compressor units (55, 57) of a fuel cell system (70) for a vehicle (80) comprising, in particular, the following steps: providing (102) initial measurement data (10) and / or model data (12) which represent a current state of the air compressor system (50) at time t0; generating (104) a state parameter (20) from the initial measurement data (10) and / or model data (12) for the fuel cell system (70); comparing (106) the state parameter (20) with a predetermined limit value (25) to determine a risk of derating the air compressor system (50) at a defined time t1 and, if necessary, determining (108) an operating strategy (30) depending on the detected state parameter (20) and the limit value (25).

Description

[0001] The present invention relates to a method for controlling an air compressor system with at least two air compressor units of a fuel cell system for a vehicle. State of the art

[0002] In vehicles where drive energy is provided by a fuel cell system, which can consist of one or more fuel cells, the oxidizing agent oxygen from the ambient air is usually used to react with hydrogen in the fuel cell to form water (or water vapor) and thus generate electrical power through electrochemical conversion.

[0003] The ambient air is to be supplied to the fuel cell system by means of an air conveying system or an air compression system, i.e. a corresponding (variable) air mass flow and a corresponding pressure level are necessary.

[0004] To achieve this pressure level, air compressor systems are known in the state of the art that can achieve higher system pressures in the cathode path of a fuel cell, which were previously unattainable with single-stage compression. Further air compressor systems are also known that utilize at least two electric motor compressors and can supply one or more fuel cells, which can also form a fuel cell stack(s).

[0005] Controlling these often complex air compressor systems for a fuel cell system has so far been a technical challenge, as high and diverse technical requirements must be taken into account while simultaneously maintaining low cost targets.

[0006] It is therefore the object of the present invention to provide a solution by means of which an air compressor system with at least two air compressor units of a fuel cell system for a vehicle can be controlled in an efficient and reliable manner. Disclosure of the invention

[0007] This object is achieved by a method for controlling an air compressor system with at least two air compressor units of a fuel cell system for a vehicle having the features of the independent claim.

[0008] According to a first aspect, the disclosure relates to a method for controlling an air compressor system with at least two air compressor units of a fuel cell system for a vehicle, which method comprises the following steps: In a first step, initial measurement data and / or model data are provided, which represent a current state of the air compressor system at time t0.

[0009] In a second step, a state parameter is created from the first measurement data and / or model data for the fuel cell system.

[0010] In a third step, the condition parameter is compared with a predefined limit value in order to determine the risk of derating of the air compressor system at a defined time t1. If the condition parameter reaches or exceeds the predefined limit value, in a fourth step, an operating strategy is determined depending on the recorded condition parameter, wherein the operating strategy comprises at least one of the following steps: - Adjusting the load distribution between at least two air compressor units; - Changing at least one operating parameter of the fuel cell system; - Changing an energy flow in the fuel cell system; - Changing an energy flow between a battery-side energy storage device in the vehicle and the fuel cell system.

[0011] For the purposes of the present invention, the term derating is understood to mean a reduction in performance, for example a reduction in a mass flow, a reduction in a pressure, a reduction in an electrical power or another variable of the air compressor system.

[0012] In a fifth step, the appropriate operating strategy is selected to bring the condition parameter below the specified limit and to reduce the identified risk of derating of the air compressor system at time t1.

[0013] A fundamental idea of ​​the present invention is that, based on a detected state parameter for the fuel cell system, a suitable operating strategy is selected in order to reduce, in particular, an identified risk of derating the air compressor system of the fuel cell system.

[0014] This approach allows the fuel cell system to operate efficiently and effectively under a wide range of predefined or changing operating conditions. This also improves the robustness of the control system, as controller switching due to limit violations is eliminated or reduced. Furthermore, the service life of the fuel cell system is extended or optimized.

[0015] Furthermore, the method according to the invention reduces the complexity of operating the fuel cell system, which is also accompanied by a reduction in the operating costs of the fuel cell system.

[0016] One possible embodiment of the method provides for the first measurement data to be temperature data of the fuel cell system, which is recorded by at least one sensor. This provides the advantage that the current state of the air compressor system can be accurately determined.

[0017] A possible embodiment of the method provides that the temperature data of the fuel cell system is formed at least as a temperature in the air compressor system, in a cathode system, in an anode system of the fuel cell system and / or in a coolant system of the fuel cell system.

[0018] Alternatively, a possible embodiment of the method further provides that the temperature data is configured at least as a temperature of a component and / or in a fluid in an air compressor system, a cathode system, an anode system, and / or a coolant system of the fuel cell system. Furthermore, however, the temperature data can also be configured as a temperature of a cooling medium of the fuel cell system, a temperature at an anode, and / or at a cathode of the fuel cell system. This provides the advantage that the current state of the air compressor system can be effectively determined.

[0019] One possible embodiment of the method provides for the at least one operating parameter of the fuel cell system to be configured as a pressure, a mass flow, a stoichiometry, or a temperature of the fuel cell system. This provides the advantage that the operating point can be changed via an operating strategy in such a way that the risk of derating is reduced.

[0020] One possible embodiment of the method provides for the limit value to be configured as a variable, adjustable limit value that depends on measurement data, operating data, and / or model data. This provides the advantage that a so-called trigger for corresponding measures can be flexibly adapted to changing operating and / or ambient conditions through a selectable operating strategy for controlling the air compressor system.

[0021] A possible embodiment of the method provides that the selection of the suitable and optimal operating strategy is based on a machine learning model that is designed to determine the expected occurrence of a performance-limiting condition of the fuel cell system and / or to react to the current occurrence of a performance-limiting condition of the fuel cell system. This achieves the advantage that efficient operation of the fuel cell system can be automated.

[0022] One possible embodiment of the method provides that the state parameter or its temporal progression over a lifetime represents an indicator of the aging state and / or energy demand of the fuel cell system or at least one component of the fuel cell system. This provides the advantage that this state parameter can be used in the method to effectively optimize the fuel cell system with respect to minimizing aging or energy demand, or both.

[0023] One possible embodiment of the method provides for the fuel cell system to have a multi-stack system, wherein the multi-stack system consists of a number of interconnected fuel cell stacks that can be operated independently of one another and / or coupled with one another. This provides the advantage that the requested energy for the vehicle can be provided flexibly to the respective operating or environmental conditions, and aging can be minimized by deactivating individual fuel cell stacks as needed or temporarily.

[0024] According to a second aspect, the disclosure relates to a fuel cell system for monitoring and / or diagnosis according to the method according to the invention.

[0025] According to a third aspect, the disclosure relates to a multi-stack system comprising at least one fuel cell stack within a fuel cell system according to the second aspect.

[0026] According to a fourth aspect, the disclosure relates to a computer program containing machine-readable instructions which, when executed on one or more computers and / or computer instances, cause the computer or computer instances to carry out the method according to the invention.

[0027] According to a fifth aspect, the disclosure relates to a machine-readable data carrier and / or download product comprising the computer program.

[0028] According to a sixth aspect, the disclosure relates to one or more computers and / or computer instances with the computer program, and / or with the machine-readable data carrier and / or the download product.

[0029] Further measures improving the invention are presented in more detail below together with the description of the preferred embodiments of the invention with reference to figures. Examples of implementation

[0030] It shows: Fig. 1 Schematic flow diagram of the method 100 for controlling an air compressor system 50 with at least two air compressor units 55, 57 of a fuel cell system for a vehicle 80; Fig. 2 Schematic representation of an air compressor system 50 for a vehicle 80 with an energy storage device 85 according to an embodiment of the present invention, and Fig. 3 Schematic representation for carrying out the method 100 according to an embodiment of the present invention.

[0031] Fig. 1 shows a schematic flow diagram of the method 100 for controlling an air compressor system 50 with at least two air compressor units 55, 57 of a fuel cell system for a vehicle 80.

[0032] In step 102, first measurement data 10 and / or model data 12 are provided, which represent a current state of the air compressor system 50 at time t0.

[0033] The first measurement data 10 can be designed as temperature data of the fuel cell system 70, which is measured by at least one sensor 75 (see Fig. 2). The model data 12 can also be based on model calculations.

[0034] Furthermore, the temperature data of the fuel cell system can be formed as at least one temperature in the air compressor system, in a cathode system, in an anode system of the fuel cell system and / or in a coolant system of the fuel cell system.

[0035] Alternatively, a possible embodiment of the method further provides that the temperature data are stored at least as a temperature of a component and / or in a fluid in an air compressor system, a cathode system, in an anode system (not shown in Fig. 1 to 3) and / or in a coolant system of the fuel cell system.

[0036] Furthermore, the temperature data may also be a temperature of a cooling medium of the fuel cell system 70, a temperature at an anode and / or at a cathode of the fuel cell system 70 (not shown in Fig. 1 to 3). This provides the advantage that the current status of the air compressor system can be effectively determined.

[0037] In step 104, a state parameter 20 is created 104 from the first measurement data 10 and / or model data 12 for the fuel cell system 70.

[0038] The state parameter 20 or its temporal progression over a lifetime can optionally be regarded as an indicator of an aging state of the fuel cell system 70 or at least one component of the fuel cell system 70.

[0039] In step 106, the state parameter 20 is compared 106 with a predetermined limit value 25 in order to determine a risk of derating of the air compressor system 50 occurring at a defined time t1, and if the state parameter 20, e.g. a temperature value, exceeds the predetermined limit value 25, an operating strategy 30 is determined 108 in step 108 depending on the detected state parameter 20 and the limit value 25. Alternatively, the determination 108 of an operating strategy 30 could also be dependent on a trigger.

[0040] The limit value 25 can preferably be designed as a variable, adjustable limit value which depends on the state parameter 20, measured data 10 and / or operating data and / or model data 12.

[0041] The operating strategy 30 includes at least one of the following steps: - Adjusting 120 a load distribution between the at least two air compressor units 55, 57. - Changing 122 at least one operating parameter 35 of the fuel cell system 70. The at least one operating parameter 35 of the fuel cell system 70 can be designed as a pressure, a mass flow, a stoichiometry or a temperature of the fuel cell system 70. - Changing 124 an energy flow in the fuel cell system 70, which is particularly relevant for multi-stack systems. - Changing 126 an energy flow between a battery-side energy storage device 85 in the vehicle 80 and the fuel cell system 70.

[0042] It should be noted that the above measures or steps 120 to 126 can be carried out in parallel or sequentially / cascaded or by any combination of the order of steps 120 to 126.

[0043] In step 110, the appropriate operating strategy 30 is selected to bring the state parameter 20 below the predetermined limit value 25 and to reduce the identified risk of derating the air compressor system 50 at time t1.

[0044] The operating strategy can be adapted iteratively, or repeatedly. This means that if a measure from step 108 of method 100 is insufficient, a further measure can be implemented. This means that the steps of the method are executed repeatedly at a specific cycle time—as is usual in the control unit.

[0045] The step 110 of selecting the suitable and optimal operating strategy can optionally be carried out on the basis of a machine learning model which is designed to determine an expected occurrence of a performance-limiting state of the fuel cell system 70 and / or to react to a current occurrence of a performance-limiting state of the fuel cell system 70.

[0046] It should also be noted that stoichiometry related to the stack-cathode path and therefore relevant to the air compressor system is also referred to as lambdaCathode. This is the ratio of air mass flow into the stack-cathode divided by the air mass flow required for the reaction in the fuel cell on the cathode side. This is also referred to as stoichiometric mass flow. Stoichiometry refers to the chemical reaction and the necessary reactants: LambdaCathode = mAir / mAirStoichio.

[0047] LambdaCathode is in normal operation over 1 ie more air mass flow is supplied than necessary for the reaction ie at the outlet of the stack cathode there is still oxygen in the exhaust gas.

[0048] With LambdaCathode=1 and ideal homogeneous distribution in the stack and ideal reaction, there would be no more oxygen in the exhaust gas.

[0049] Limiting factors for the air compressor units can include, for example, temperature limitations of power electronic components of the fuel cell system.

[0050] The following additional limitations, which are given as examples, can be applied to one or both air compressor units 55, 57 (see Fig. 2) occur and are applied as the respective limit value (25) with the associated state parameter (20) (examples, possibly not complete): - Temperature limitation power electronics - Temperature limitation capacitor - Temperature limitation stator - Temperature limitation rotor - Temperature limitation of radial bearings (usually two) - Temperature limitation of axial bearings (usually one) - Power supply, because if the voltage is too low then the required load may no longer be reached. - The air compressor units can be integrated differently into the vehicle's electrical system 80, ie a voltage that is too low or too high can only occur at one unit / inverter at a time. - Performance limitation - Power limitation - Cooling air supply for the bearings (temperatures, mass flow) - Coolant supply unit, power electronics (temperatures, mass flow) - Limiting speeds, nmin for idle speed, nmax - Limitation of compressor characteristic map, especially surge limit, plugging limit - NVH limits (vibrations, noise, etc.) - Rotordynamic limits. - Limits for turbine regarding humidity, drops, water in the exhaust gas. - Limits for freeze start e.g. warm-up gradients

[0051] The method 100 according to the invention can react reactively to a current occurrence of limitations and / or predictively to an expected occurrence of limitations of the fuel cell system 70.

[0052] The method 100 according to the invention can additionally / optionally also be carried out diagnostically (for diagnoses).

[0053] The method 100 according to the invention can be carried out statically and / or adaptively and / or learning-based, e.g. by means of AI / ML methods.

[0054] The method 100 according to the invention is not limited to two air compressor units and can also be transferred to several air compressor units if topologies with three or more air compressor units are required.

[0055] Fig. 2 shows a schematic representation of an air compressor system 50 for a vehicle 80 with an energy storage device 85 according to an embodiment of the present invention.

[0056] The air compressor system 50 has in the example of Fig. 2 includes a first air compressor unit 55 and a second air compressor unit 57. A plurality of air compressor units can be implemented in the air compressor system 50.

[0057] The air compressor system 50 preferably has two electric motor-driven drive shafts (not shown). The interconnection of the air compressor units 55, 57 can be implemented according to topologies known in the prior art and will therefore not be explained in detail here.

[0058] The Fig. 2 exemplary fuel cell system 70 contains a multi-stack system 95, wherein the multi-stack system 95 consists of a number of interconnected fuel cell stacks 90, which can be operated independently of one another and / or coupled with one another.

[0059] The fuel cell system 70 further comprises at least one sensor 75 for providing first measurement data 10 and / or model data 12.

[0060] The vehicle 80, in which the fuel cell system 70 according to the invention can be implemented, has an energy storage device 85 which is supplied with energy by the fuel cell system and / or by the vehicle drive in recuperation mode.

[0061] Fig. 3 shows a schematic representation for carrying out the method 100 according to an embodiment of the present invention.

[0062] In particular, the various and diverse intervention options are clearly illustrated in the form of different levels 1 to 4 in order to control the air compressor system 50 of the fuel cell system 70 depending on the detected state parameter 20 and the limit value 25.

[0063] These will be described below with reference to individual process steps of the process 100 according to the Fig. 1 and Fig. 2 will be explained.

[0064] The first and highest level 1 (= LevCtr1) for a vehicle control / total energy management comprises the step of changing 126 an energy flow between the battery-side energy storage 85 in the vehicle 80 and the fuel cell system 70.

[0065] This degree of freedom at level 1 of the distribution between energy converters and energy storage devices can be used according to the invention to avoid derating. The energy storage devices (e.g., batteries) can provide at least temporary relief. In addition, the vehicle's trajectory planning can be adjusted, e.g., by reducing speed on an uphill stretch.

[0066] Level 2 (= LevCtr2) for an energy converter overall control / multistack power split includes the step of changing 124 an energy flow in the fuel cell system 70.

[0067] This degree of freedom at level 2 of the distribution between the individual stacks is used according to the invention to avoid derating (50). If air systems of other stacks do not have a derating risk or if no other limitations exist, then changing the power distribution between the multiple stacks can reduce the load on the respective system or units that have a derating risk.

[0068] It should be noted that the load distribution between air compressor units 55 and 57 occurs at one air system level. In this example, this is implemented via level 4 (= LevCtr4). This is the first intervention, because the other levels 1 and 3 do not yet need to be taken into account. Only when the load distribution between 55 and 57 is not yet sufficient with LevCtrl4 do additional levels come into play to make further adjustments or changes to control the air compressor system.

[0069] Level 3 (= LevCtr3) for an overall stack control / water management / cooling systems comprises the step of changing 122 at least one operating parameter 35 of the fuel cell system 70. - For each stack i=1,2,3,4, etc. there are individual operating conditions with degrees of freedom. - These degrees of freedom relate in particular to water management, where pressure, lambda cathode (excess air) and stack temperature are important variables that must be coordinated with one another. - LevCtrl3 can be implemented individually for each stack ie LevCtrl3-1, LevCtrl3-2, etc.. - The degrees of freedom within this system level can be used to avoid derating (number 40 in Level 3). - For example, the degree of freedom "cathode pressure in the stack vs. lambda cathode path stack" can be used here to relieve the load on an air compressor unit. This can be done either stationary / permanently (number 41 in Level 3) or temporarily (numbers 43, 44 in Level 3). - Temporary measures can be taken because the stack has a certain Water storage capacity means that the membrane humidity does not change as dynamically as the mass flow or pressure in the air system. - The stack temperature can be lowered (number 42 in Level 3) to reduce the pressure requirements in particular. - Can the cooling be improved (number 45 in level 3) e.g. by improved intercooler or by improved cooling of the power electronics.

[0070] Level 4 (= LevCtr4) shows an example of a procedure for controlling the operation of the air compressor system 50 with the units 55, 57 (see Fig. 2) to regulate or optimize. The following measures can be taken within Level 4: - If intervention is necessary due to limitations being reached, the degree of freedom within LevCtrl4 should preferably be used. This way, the higher-level levels or LevCtrl 1, 2, and 3 are not affected until further notice. Alternatively, adaptation can also take place across multiple levels. - The units 55, 57 are operated according to the “normal” regulation / control of the entire air system (see numbers 11a, 11b in Level 4 of the Fig. 3). For this purpose, all other actuators of the air system are controlled accordingly (see number 10b in Level 4 of the Fig. 3). - Based on measured values ​​and models, a risk of derating (see numbers 12, 14 in Level 4 of the Fig. 3) can be determined. This can be done for current operation or predictively. For example, a temperature in the power electronics or stator becomes too high. - If a risk or a limitation approach or a limitation violation is detected, then measures are initiated (see numbers 20, 30 of Level 4 in Fig. 3). - If the machine of air compressor unit 55 is at a limit, the load can be reduced or the operating point can be changed so that the limit is no longer reached or the distance to the limit is not further reduced (predictive). To compensate for this, machine 57 is subjected to a correspondingly higher load or a changed operating point (see number 32 in Level 4 of the Fig. 3). This means the balance between both machines is changed. - At number 34 of level 4 in Fig. Figure 3 shows the opposite situation. Unit 57 is / will be reaching a limit. The measure here is also to change the balance between the two machines 55 and 57. - When changing the balancing of the machines, the entire air system control is involved, ie also the corresponding other actuators (see number 30b of the Fig. 3) will be adjusted. - If both machines are at risk of derating at the same time or almost at the same time (whereby there may be different limitations, e.g. in one machine the temperature of the power electronics is too high, in the other machine the cooling air is no longer cooled sufficiently or the pump limit is reached), ie number 22 in level 4 of the Fig. 3, then measures can be carried out outside the air system control LevCtrl4. - These measures can be used sequentially or in parallel. - Derating can be avoided by adapting the operation via LevCtrl3 and / or LevCtrl2 and / or LevCtrl1.

Claims

[1] Method (100) for controlling an air compressor system (50) with at least two air compressor units (55, 57) of a fuel cell system (70) for a vehicle (80), comprising the following steps: - Providing (102) first measurement data (10) and / or model data (12) which represent a current state of the air compressor system (50) at time t0; - creating (104) a state parameter (20) from the first measurement data (10) and / or model data (12) for the fuel cell system (70); - comparing (106) the state parameter (20) with a predetermined limit value (25) in order to determine a risk of derating of the air compressor system (50) at a defined time t1 and - if the state parameter (20) reaches or exceeds the specified limit value (25), step (108) takes place, - Determining (108) an operating strategy (30) as a function of the detected state parameter (20) and the limit value (25), wherein the operating strategy (30) comprises at least one of the following steps: ◯ Adjusting (120) a load distribution between the at least two air compressor units (55, 57); ◯ Changing (122) at least one operating parameter (35) of the fuel cell system (70); ◯ Changing (124) an energy flow in the fuel cell system (70); ◯ Changing (126) an energy flow between a battery-side energy storage device (85) in the vehicle (80) and the fuel cell system (70); - selecting (110) the appropriate operating strategy (30) to bring the state parameter (20) below the predetermined limit value (25) and to reduce the identified risk of derating of the air compressor system (50) at time t1. [2] Method (100) according to claim 1, wherein the first measurement data (10) are formed as temperature data of the fuel cell system (70), which are detected by at least one sensor (75). [3] Method (100) according to claim 2, wherein the temperature data of the fuel cell system (70) is formed at least as a temperature in the air compressor system (50), in a cathode system, in an anode system of the fuel cell system (70) and / or in a coolant system of the fuel cell system (70). [4] Method (100) according to one of the preceding claims, wherein the at least one operating parameter (35) of the fuel cell system (70) is designed as a pressure, a mass flow, a stoichiometry or a temperature of the fuel cell system (70). [5] Method (100) according to one of the preceding claims, wherein the limit value (25) is designed as a variable adjustable limit value which is dependent on measurement data (10) and / or operating data and / or model data (12). [6] Method (100) according to one of the preceding claims, wherein the selection (110) of the suitable and optimal operating strategy (30) is carried out on the basis of a machine learning model which is designed to determine an expected occurrence of a performance-limiting state of the fuel cell system (70) and / or to react to a current occurrence of a performance-limiting state of the fuel cell system (70). [7] Method (100) according to one of the preceding claims, wherein the state parameter (20) or its temporal course over a lifetime represents an indicator for an aging state of the fuel cell system (70) or at least one component of the fuel cell system (70). [8] Method (100) according to one of the preceding claims, wherein the fuel cell system (70) comprises a multi-stack system (95), wherein the multi-stack system (95) consists of a number of interconnected fuel cell stacks (90) which can be operated independently of one another and / or coupled to one another. [9] Fuel cell system (70) for monitoring and / or diagnosing according to a method according to one of the preceding claims 1 to 8. [10] Multistack system (95) comprising at least one fuel cell stack (90) within a fuel cell system (70) according to claim 8. [11] Computer program containing machine-readable instructions which, when executed on one or more computers and / or computer instances, cause the computer or computer instances to carry out the method according to one of claims 1 to 8 and / or to control the fuel cell system (70) according to one of claims 1 to 8. [12] Machine-readable data carrier and / or download product with the computer program according to claim 11. [13] One or more computers and / or computer instances with the computer program according to claim 11, and / or with the machine-readable data carrier and / or download product according to claim 12.

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