WO2009153004A1 - Control module for a fuel cell system, fuel cell system with the control module and method for controlling a fuel cell system - Google Patents

Control module for a fuel cell system, fuel cell system with the control module and method for controlling a fuel cell system Download PDF

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Publication number
WO2009153004A1
WO2009153004A1 PCT/EP2009/004261 EP2009004261W WO2009153004A1 WO 2009153004 A1 WO2009153004 A1 WO 2009153004A1 EP 2009004261 W EP2009004261 W EP 2009004261W WO 2009153004 A1 WO2009153004 A1 WO 2009153004A1
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WO
WIPO (PCT)
Prior art keywords
fuel cell
stack
cell system
control module
val
Prior art date
Application number
PCT/EP2009/004261
Other languages
French (fr)
Inventor
Helmut Müller
Pere Antoni Pastor Nigorra
Sven Schmalzriedt
Christoph Ziegler
Original Assignee
Daimler Ag
Ford Global Technologies, Llc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Daimler Ag, Ford Global Technologies, Llc filed Critical Daimler Ag
Publication of WO2009153004A1 publication Critical patent/WO2009153004A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04291—Arrangements for managing water in solid electrolyte fuel cell systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0432—Temperature; Ambient temperature
    • H01M8/04358—Temperature; Ambient temperature of the coolant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0432—Temperature; Ambient temperature
    • H01M8/04365—Temperature; Ambient temperature of other components of a fuel cell or fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04604—Power, energy, capacity or load
    • H01M8/04619—Power, energy, capacity or load of fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04492—Humidity; Ambient humidity; Water content
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04992—Processes for controlling fuel cells or fuel cell systems characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • Control module for a fuel cell system, fuel cell system with the control module and method for controlling a fuel cell system
  • the invention relates to a control module for a fuel cell system comprising at least one fuel cell stack, with an input interface for receiving a temperature parameter for the temperature of the fuel cell stack, with an output interface for outputting a control signal for triggering a life cycle-increasing measure for the fuel cell system and/or components thereof, and with an evaluation device which is designed for evaluating the temperature parameter and for generating the control signal based on the evaluation in a program- technological and/or circuitry-technological manner.
  • the invention further relates to a fuel cell system with this control module, and a method for controlling one or the fuel cell system.
  • Fuel cell systems in addition to the application in automobiles, are used as alternative energy generators for the drive train, also as stationary systems, for example in the form of current generators for houses or the like, but also for portable applications, as for example as small fuel cells for electrical/electronic devices.
  • the fuel cell systems usually have one or several fuel cells, which are organized in one or several fuel cell stacks.
  • An electrochemical process is operated for energy generation, wherein a fuel, usually hydrogen, is converted with an oxidation means, usually oxygen or ambient air, and chemical energy is converted to electrical energy.
  • a membrane separating a cathode region from an anode region in the fuel cell stack or in the fuel cells plays an important part in the electrochemical process, as it separates the fuel from the oxidation means on the one hand, and has to be formed permeable for hydrogen ions (protons). During the operation, it is necessary that this membrane is always sufficiently humidified, so as to ensure a good proton conductivity and to prevent premature wear and therewith a reduced life cycle.
  • PAJ 2005150025 A discloses for example a fuel cell system, which measures the temperature of the expelled process gas for the stabilization of the water balance, and controls the maximum output power of the fuel cell system in dependence on the temperature of the expelled process gases.
  • a control module that is, a device for the control, which is suitable and/or designed for a fuel cell system.
  • the control module is for example represented as a data processing unit or as a circuit.
  • the fuel cell system is preferably meant for the automotive area, in particular for generating the energy of the drive train for a vehicle.
  • the fuel cell system can also be formed as a stationary or a portable fuel cell system, in particular portable by hand, for arbitrary other applications.
  • the fuel cell system includes at least one fuel cell stack, which comprises at least one fuel cell, but preferably a plurality of fuel cells, in particular more than 100 fuel cells.
  • the control module has an input interface for the wired and/or wireless acceptance of a temperature parameter, wherein the temperature parameter is chosen chacateristically for the temperature, in particular the current or operating temperature of the fuel cell stack, in particular the fuel cells and/or the membrane.
  • the control module further includes an output interface, which is formed for the output of a control signal.
  • the control signal serves for triggering a life cycle-increasing measure for the fuel cell system and/or components thereof or particularly for the membrane or membranes of the fuel cell system.
  • Life cycle-increasing measures are preferably measures which transfer, directly or indirectly, a current condition of the fuel cell system with a first life cycle expectation - in particular for the membrane or the membranes - into a second condition of the fuel cell system with a second life cycle expectation, wherein the second life cycle expectation is estimated to be larger than the first life cycle expectation.
  • An evaluation apparatus of the control module is formed for generating the control signal based on the evaluation in a program-technological or circuitry-technological manner.
  • the evaluation comprises the determination of an accumulation value of the temperature parameter and/or a variable derived therefrom or equivalent thereto, over time. Metaphorically speaking, the surface under the graph of the temperature parameter or the derived variable is thus determined when plotting the temperature parameter over time.
  • the accumulation value is determined as an integral, in particular numerical integral, Riemann integral, Cauchy integral over time, or a corresponding numerical conversion is used.
  • the invention thus permits an improved identification of the "stack- or membrane- damaging" operating region, and based thereon, a higher peak power of the fuel cell system with simultaneous minimization of the stack ageing, and this with a congenial system assembly compared to the state of the art.
  • the invention further enables a more exact and more specific regulation or control of stack- or membrane-protecting countermeasures and a more statistic sensing of stack-damaging operating modi.
  • the derived variable is formed as an offset-adjusted temperature parameter in a preferred embodiment of the invention.
  • the offset value is particularly formed as a temperature constant, which describes a maximum threshold prior to reaching a region with a life cycle-reducing temperature. This maximum threshold can for example be determined by laboratory tests.
  • the accumulation value only increases as a result in this embodiment, if the temperature parameter is above the maximum threshold, and reduces in contrast, if the temperature parameter is below the maximum threshold.
  • the evaluation apparatus is formed so as to compare the accumulation value with an accumulation constant.
  • This accumulation constant is also an estimated or measured expected variable which shows a threshold for a permanent or life-cycle reducing damage of the membranes.
  • the control signal is preferably activated by the accumulation value when exceeding the accumulation constant.
  • the control signal can be generated in dependence on, that is, for example proportional to the difference between the accumulation value and the accumulation constant.
  • the accumulation value can also be formed by a function of the temperature parameter. It is for example possible that the temperature parameter is entered into a broken function, so as to supplement a weighting function and the like. It is also possible and within the scope of the invention that the accumulation value takes up a central point in a complex control or regulation, as for example a fuzzy logic control, a neural network, an adaptive or non-adaptive controller etc.
  • the control signal is formed for the power control of the fuel cell system in a preferred embodiment of the invention.
  • the control signal can e.g. be formed for triggering a humidifying apparatus or for increasing the cooling performance.
  • the control signal can further also be formed for controlling a plurality of the mentioned or further countermeasures for reducing the temperature and/or for increasing the humidity.
  • a further object of the invention relates to a fuel cell system with at least one fuel cell stack, which is characterized by the control module as described above or according to one of the preceding claims.
  • the fuel cell system is used as a mobile fuel cell system in a vehicle.
  • a vehicle with such a fuel cell system is also disclosed.
  • the fuel cell system preferably has a temperature sensor, which is formed and/or arranged in a convenient arrangement for monitoring the starting temperature of a coolant for the fuel cell stack and for outputting the temperature parameter from the temperature sensor to the input interface.
  • the starting temperature of the coolant depicts a parameter for the temperature of the fuel cell stack which can be determined easiliy and in a cost- effective manner.
  • a last object of the invention relates to a method for controlling a fuel cell system with the characteristics of claim 11 , wherein the fuel cell system is preferably formed according to one of the preceding claims and/or provided with a control module according to one of the preceding claims. It is suggested according to the invention, that a temperature parameter of the fuel cell stack is accumulated as an accumulation value over time and that life cycle-increasing measures are initiated in dependence on the accumulation value.
  • FIG. 1 a fuel cell system with a control module as an example of an embodiment of the invention in a schematic block diagram
  • figure 2 a flow chart of a control strategy for controlling a fuel cell system.
  • Figure 1 shows a fuel cell system 1 with a fuel cell stack 2, which comprises at least one fuel cell, which shows an anode and a cathode region 3 a, b, which are separated from one another by a membrane 4, in particular a proton-conducting polymer electrolyte membrane (PEM).
  • the fuel cell system 1 is for example arranged in a vehicle (not shown) and serves for energy generation for the drive train of the vehicle.
  • a temperature sensor 5 is provided, which senses the temperature of the fuel cell stack 2, in particular as relative measurement of the temperature of the coolant in the region of the coolant exit 6, and passes it as a temperature parameter to a control module 8 via an input interface 7.
  • the temperature parameter is observed and evaluated over time in the control module 8, wherein the evaluation will be explained in a detailed manner in the following in connection with figure 2.
  • a control signal is generated based on the evaluation, which is outputted via an output interface 9 and transferred to the control of the fuel cell system 1.
  • control signal 9 effects a life cycle-increasing measure in the fuel cell system in its most general development, the control signal 9 particularly leads to a power control, in particular a power minimization of the maximum output power of the fuel cell system with a corresponding evaluation of the temporal behavior of the temperature parameter.
  • FIG. 2 shows a flow chart for illustrating the method according to the invention.
  • a temperature measurement is carried out by the temperature sensor 5, and a temperature parameter T_stack is determined.
  • the temperature parameter T_stack is equivalent to, or as a relative measuring variable, at least dependent on the internal fuel cell stack temperature.
  • hot _op_ val J(T _ stack - T _ stack _ th)dt , t
  • T_stack temperature parameter for the internal stack temperature, that is, the fuel cell stack temperature
  • T_stack_th limit temperature, where drying out effects of the membrane 4 do not yet result during permanent operation
  • hot_op_val hot operation integral value, corresponds to one or the accumulation value, and is a measure for the current or accumulated load on the membrane 4.
  • the accumulation value hot_op_val is checked if it is larger or smaller than zero. With values smaller than zero it means that no accumulated load is present, and in a step 40, the current value for the accumulation value hot_op_val and the observation period t is set to zero, and the calculation is repeated. By setting the current accumulation value to the value 0, it is ensured that the accumulation value hot_op_val cannot hold any negative values.
  • the accumulation value hot_op_val is larger than zero, it is checked in a step 50, if the accumulation value has already exceeded a threshold hot_op_val_th.
  • This threshold hot_op_val_th is also determined experimentally from life cycle tests or estimated theoretical Iy and describes, how long a fuel cell system 1 can be operated above the limit temperature T_stack_th without resulting in damaging drying out of the membrane 4.
  • the calculation of the integral is continued in step 20.
  • This case is for example present if the fuel cell system 1 is in an operating condition with a current fuel cell stack temperature T_stack larger than the limit temperature T_stack_th, but the temporal duration in this operating condition is not yet critical. It is then further possible, that the accumulation value increases further, until the threshold hot_op_val_th is exceeded, or that the accumulation value is disintegrated when the temperature parameter T_stack becomes smaller than the limit temperature T_stack_th.
  • a power reduction of the output power of the fuel cell system takes place in a step 60 in dependence on the difference between the accumulation value and the threshold.
  • a cooling of the temperature of the fuel celll stack 2 is expected as the effect of the power reduction, and the monitoring starts again at step 10.
  • a "load energy” which is defined as the product or integral of the temperature above a temperature threshold and the time. Life cycle-obtaining measures are initiated in dependence on the value of the load energy.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
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Abstract

The invention is based on the object to suggest a control module, a fuel cell system with the control module, and a method for controlling the fuel cell system with the aim to improve the life cycle of the fuel cell system or components thereof with a simultaneous good power output. A control module (8) is suggested for a fuel cell system (1) for this, which has at least a fuel cell stack (2), with an input interface (7) for receiving a temperature parameter T_stack for the temperature of the fuel cell stack (2), with an output interface (9) for outputting a control signal for triggering a life cycle-increasing measure for the fuel cell system (1) and/or components (4) thereof, which is formed in a program-technological and/or circuitry-technological manner for evaluating the temperature parameter and for generating the control signal based on the evaluation, wherein the evaluation comprises the determination of an accumulation value hot_op_val of the temperature parameter T_stack and/or a variable T_stack-T_stack_th derived therefrom over the time t.

Description

Control module for a fuel cell system, fuel cell system with the control module and method for controlling a fuel cell system
The invention relates to a control module for a fuel cell system comprising at least one fuel cell stack, with an input interface for receiving a temperature parameter for the temperature of the fuel cell stack, with an output interface for outputting a control signal for triggering a life cycle-increasing measure for the fuel cell system and/or components thereof, and with an evaluation device which is designed for evaluating the temperature parameter and for generating the control signal based on the evaluation in a program- technological and/or circuitry-technological manner. The invention further relates to a fuel cell system with this control module, and a method for controlling one or the fuel cell system.
Fuel cell systems, in addition to the application in automobiles, are used as alternative energy generators for the drive train, also as stationary systems, for example in the form of current generators for houses or the like, but also for portable applications, as for example as small fuel cells for electrical/electronic devices.
The fuel cell systems usually have one or several fuel cells, which are organized in one or several fuel cell stacks. An electrochemical process is operated for energy generation, wherein a fuel, usually hydrogen, is converted with an oxidation means, usually oxygen or ambient air, and chemical energy is converted to electrical energy.
A membrane separating a cathode region from an anode region in the fuel cell stack or in the fuel cells plays an important part in the electrochemical process, as it separates the fuel from the oxidation means on the one hand, and has to be formed permeable for hydrogen ions (protons). During the operation, it is necessary that this membrane is always sufficiently humidified, so as to ensure a good proton conductivity and to prevent premature wear and therewith a reduced life cycle.
The specification PAJ 2005150025 A (publication number) discloses for example a fuel cell system, which measures the temperature of the expelled process gas for the stabilization of the water balance, and controls the maximum output power of the fuel cell system in dependence on the temperature of the expelled process gases.
It is the object of the invention to suggest a control module, a fuel cell system with the control module, and a method for controlling the fuel cell system with the aim to extend the life cycle of the fuel cell system or components thereof with a simultaneous good power output.
This object is solved by a control module with the characteristics of claim 1 , a fuel cell system with the characteristics of claim 9, and a method for controlling one or the fuel cell system with the characteristics of claim 11. Preferred or advantageous embodiments of the invention result from the dependent claims, the following description and the enclosed figures.
According to the invention, a control module, that is, a device for the control, is suggested, which is suitable and/or designed for a fuel cell system. The control module is for example represented as a data processing unit or as a circuit.
The fuel cell system is preferably meant for the automotive area, in particular for generating the energy of the drive train for a vehicle. The fuel cell system can also be formed as a stationary or a portable fuel cell system, in particular portable by hand, for arbitrary other applications.
The fuel cell system includes at least one fuel cell stack, which comprises at least one fuel cell, but preferably a plurality of fuel cells, in particular more than 100 fuel cells.
The control module has an input interface for the wired and/or wireless acceptance of a temperature parameter, wherein the temperature parameter is chosen chacateristically for the temperature, in particular the current or operating temperature of the fuel cell stack, in particular the fuel cells and/or the membrane. The control module further includes an output interface, which is formed for the output of a control signal. The control signal serves for triggering a life cycle-increasing measure for the fuel cell system and/or components thereof or particularly for the membrane or membranes of the fuel cell system.
Life cycle-increasing measures are preferably measures which transfer, directly or indirectly, a current condition of the fuel cell system with a first life cycle expectation - in particular for the membrane or the membranes - into a second condition of the fuel cell system with a second life cycle expectation, wherein the second life cycle expectation is estimated to be larger than the first life cycle expectation.
An evaluation apparatus of the control module is formed for generating the control signal based on the evaluation in a program-technological or circuitry-technological manner.
It is suggested within the scope of the invention, that the evaluation comprises the determination of an accumulation value of the temperature parameter and/or a variable derived therefrom or equivalent thereto, over time. Metaphorically speaking, the surface under the graph of the temperature parameter or the derived variable is thus determined when plotting the temperature parameter over time.
It is thereby within the scope of the invention, that the accumulation value is determined as an integral, in particular numerical integral, Riemann integral, Cauchy integral over time, or a corresponding numerical conversion is used.
It is one consideration of the invention that, with a continuous operation of fuel cells at high temperatures, an accelerated ageing, in particular of the membrane material occurs and a reduction of the life cycle of the fuel cell or the fuel cell stack accompanies this. This effect occurs in particular in combination with dry or under-satisfied operating conditions.
So as to avoid a premature wear of the membrane or of the fuel cells, it thus appears to be necessary - as known from the state of the art - to exclude an operation at temperatures which are too high and/or having a humidity which is too low. According to the invention, it is suggested in this regard, to limit the operating duration at high temperatures and/or low humidity within a sensible scope. As the evaluation takes place via the determination of an accumulation value, it is ensured that life cycle- increasing measures are not initiated already when a measured temperature lies outside a limit, but the membranes are not sufficiently humidified, but only if an actual damage of the fuel cell system, in particular of the emembranes has to be feared. An unnecessary impairment of the energy supply behavior of the fuel cell system or the entire drive behavior of a vehicle driven with the fuel cell system is avoided in this manner.
Short-term "overshooters", which occur for example with time-limited, very high power demands (e.g. driving up-hill, "kick-downs" etc.) can thus be tolerated in spite of the exceeded temperature. Countermeasures are initiated only with a longer presence of these operating conditions, which lead especially to a drying out of the membrane and thus to a shortening of the life cycle of the fuel cell system, countermeasures are initiated. The invention thus permits an improved identification of the "stack- or membrane- damaging" operating region, and based thereon, a higher peak power of the fuel cell system with simultaneous minimization of the stack ageing, and this with a congenial system assembly compared to the state of the art. The invention further enables a more exact and more specific regulation or control of stack- or membrane-protecting countermeasures and a more statistic sensing of stack-damaging operating modi.
The derived variable is formed as an offset-adjusted temperature parameter in a preferred embodiment of the invention. The offset value is particularly formed as a temperature constant, which describes a maximum threshold prior to reaching a region with a life cycle-reducing temperature. This maximum threshold can for example be determined by laboratory tests. The accumulation value only increases as a result in this embodiment, if the temperature parameter is above the maximum threshold, and reduces in contrast, if the temperature parameter is below the maximum threshold.
In a preferred embodiment of the invention, the evaluation apparatus is formed so as to compare the accumulation value with an accumulation constant. This accumulation constant is also an estimated or measured expected variable which shows a threshold for a permanent or life-cycle reducing damage of the membranes. The control signal is preferably activated by the accumulation value when exceeding the accumulation constant. In alternative embodiments, the control signal can be generated in dependence on, that is, for example proportional to the difference between the accumulation value and the accumulation constant.
Even though a determination of the accumulation value was only disclosed in a very simple depiction in the above, it shall be pointed out that the accumulation value can also be formed by a function of the temperature parameter. It is for example possible that the temperature parameter is entered into a broken function, so as to supplement a weighting function and the like. It is also possible and within the scope of the invention that the accumulation value takes up a central point in a complex control or regulation, as for example a fuzzy logic control, a neural network, an adaptive or non-adaptive controller etc.
The control signal is formed for the power control of the fuel cell system in a preferred embodiment of the invention. In alternative embodiments, the control signal can e.g. be formed for triggering a humidifying apparatus or for increasing the cooling performance. The control signal can further also be formed for controlling a plurality of the mentioned or further countermeasures for reducing the temperature and/or for increasing the humidity.
A further object of the invention relates to a fuel cell system with at least one fuel cell stack, which is characterized by the control module as described above or according to one of the preceding claims.
In a preferred constructive realization, the fuel cell system is used as a mobile fuel cell system in a vehicle. According to the invention, a vehicle with such a fuel cell system is also disclosed.
The fuel cell system preferably has a temperature sensor, which is formed and/or arranged in a convenient arrangement for monitoring the starting temperature of a coolant for the fuel cell stack and for outputting the temperature parameter from the temperature sensor to the input interface. The starting temperature of the coolant depicts a parameter for the temperature of the fuel cell stack which can be determined easiliy and in a cost- effective manner. A last object of the invention relates to a method for controlling a fuel cell system with the characteristics of claim 11 , wherein the fuel cell system is preferably formed according to one of the preceding claims and/or provided with a control module according to one of the preceding claims. It is suggested according to the invention, that a temperature parameter of the fuel cell stack is accumulated as an accumulation value over time and that life cycle-increasing measures are initiated in dependence on the accumulation value.
Further characteristics, advantages and effects of the invention result from the following description of preferred embodiments of the invention. It shows thereby:
figure 1 a fuel cell system with a control module as an example of an embodiment of the invention in a schematic block diagram;
figure 2 a flow chart of a control strategy for controlling a fuel cell system.
Figure 1 shows a fuel cell system 1 with a fuel cell stack 2, which comprises at least one fuel cell, which shows an anode and a cathode region 3 a, b, which are separated from one another by a membrane 4, in particular a proton-conducting polymer electrolyte membrane (PEM). The fuel cell system 1 is for example arranged in a vehicle (not shown) and serves for energy generation for the drive train of the vehicle.
So as to prevent life cycle-reducing operating conditions of the fuel cell system 1 , in particular in view of the membrane 4, a temperature sensor 5 is provided, which senses the temperature of the fuel cell stack 2, in particular as relative measurement of the temperature of the coolant in the region of the coolant exit 6, and passes it as a temperature parameter to a control module 8 via an input interface 7.
The temperature parameter is observed and evaluated over time in the control module 8, wherein the evaluation will be explained in a detailed manner in the following in connection with figure 2. A control signal is generated based on the evaluation, which is outputted via an output interface 9 and transferred to the control of the fuel cell system 1.
The control signal effects a life cycle-increasing measure in the fuel cell system in its most general development, the control signal 9 particularly leads to a power control, in particular a power minimization of the maximum output power of the fuel cell system with a corresponding evaluation of the temporal behavior of the temperature parameter.
Figure 2 shows a flow chart for illustrating the method according to the invention. In a first step 10, a temperature measurement is carried out by the temperature sensor 5, and a temperature parameter T_stack is determined. The temperature parameter T_stack is equivalent to, or as a relative measuring variable, at least dependent on the internal fuel cell stack temperature.
In a next step 20, the following equation is calculated:
hot _op_ val = J(T _ stack - T _ stack _ th)dt , t
wherein the parameters are defined as follows:
T_stack: temperature parameter for the internal stack temperature, that is, the fuel cell stack temperature;
T_stack_th: limit temperature, where drying out effects of the membrane 4 do not yet result during permanent operation;
hot_op_val: hot operation integral value, corresponds to one or the accumulation value, and is a measure for the current or accumulated load on the membrane 4.
In a third step 30, the accumulation value hot_op_val is checked if it is larger or smaller than zero. With values smaller than zero it means that no accumulated load is present, and in a step 40, the current value for the accumulation value hot_op_val and the observation period t is set to zero, and the calculation is repeated. By setting the current accumulation value to the value 0, it is ensured that the accumulation value hot_op_val cannot hold any negative values.
In the case that the accumulation value hot_op_val is larger than zero, it is checked in a step 50, if the accumulation value has already exceeded a threshold hot_op_val_th. This threshold hot_op_val_th is also determined experimentally from life cycle tests or estimated theoretical Iy and describes, how long a fuel cell system 1 can be operated above the limit temperature T_stack_th without resulting in damaging drying out of the membrane 4.
In the case that the threshold hot_op_val_th is not exceeded, the calculation of the integral is continued in step 20. This case is for example present if the fuel cell system 1 is in an operating condition with a current fuel cell stack temperature T_stack larger than the limit temperature T_stack_th, but the temporal duration in this operating condition is not yet critical. It is then further possible, that the accumulation value increases further, until the threshold hot_op_val_th is exceeded, or that the accumulation value is disintegrated when the temperature parameter T_stack becomes smaller than the limit temperature T_stack_th.
In the case that the threshold hot_op_val_th is exceeded, a power reduction of the output power of the fuel cell system takes place in a step 60 in dependence on the difference between the accumulation value and the threshold.
A cooling of the temperature of the fuel celll stack 2 is expected as the effect of the power reduction, and the monitoring starts again at step 10.
Following a general consideration of the invention, it is suggested for the apparatus or the method to calculate a "load energy", which is defined as the product or integral of the temperature above a temperature threshold and the time. Life cycle-obtaining measures are initiated in dependence on the value of the load energy.

Claims

Claims
1. Control module (8) for a fuel cell system (1), comprisisng at least one fuel cell stack (2),
with an input interface (7) for receiving a temperature parameter (T_stack) for the temperature of the fuel cell stack (2),
with an output interface (9) for outputting a control signal for triggering a life cycle- increasing measure for the fuel cell system (1) and/or components (4) thereof, and
with an evaluation device, which is formed for the evaluation of the temperature parameter and for the generation of the control signal based on the evaluation in a program-technological and/or circuitry-technological manner,
characterized in that
the evaluation comprises the determination of an accumulation value (hot_op_val) of the temperature parameter (T_stack) and / or a variable (T_stack-T_stack_th) derived therefrom over time (t).
2. Control module (8) according to claim 1 , characterized in that the accumulation value (hot_op_val) is determined as an integral, numerical integral, Riemann integral, Cauchy integral over time or their numerical conversion.
3. Control module (8) according to claim 1 or 2, characterized in that the derived variable is formed as an offset-adjusted temperature parameter (T_stack-T_stack_th).
4. Control module (8) according to claim 3, characterized in that the offset (T_stack_th) is formed as a temperature constant which describes a maximum threshold for a life cycle- lowering temperature.
5. Control module (8) according to one of the preceding claims, characterized in that the accumulation value (hot_op_val) is compared to an accumulation constant (hot_op_val_th).
6. Control module (8) according to claim 5, characterized in that the control signal is activated by the accumulation value (hot_op_val) when the accumulation constant (hot_op_val_th) is exceeded.
7. Control module (8) according to one of claims 5 or 6, characterized in that the control signal is determined in dependence on the difference between accumulation constant (hot_op_val_th) and the accumulation value (hot_op_val).
8. Control module (8) according to one of the preceding claims, characterized in that the control signal is formed for the power control of the fuel cell system (1).
9. Fuel cell system (1) with at least one fuel cell stack (2), characterized by the control module (8) according to one of the preceding claims.
10. Fuel cell system (1) according to claim 9, characterized by a temperature sensor (5), which is formed and/or arranged for monitoring the starting temperature of a coolant for the fuel cell stack (1) and for outputting the temperature parameter to the input interface (7).
11. Method for controlling a fuel cell system (1), preferably according to one of the preceding claims and/or with a control module (8) according to one of the preceding claims, wherein a temperature parameter (T_stack) of the fuel cell stack (1) is accumulated over time (t) as an accumulation value (hot_op_val) and that life cycle- increasing measures are initiated in dependence on the accumulation value (hot_op_val).
PCT/EP2009/004261 2008-06-19 2009-06-12 Control module for a fuel cell system, fuel cell system with the control module and method for controlling a fuel cell system WO2009153004A1 (en)

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DE102008029176.5 2008-06-19
DE102008029176A DE102008029176A1 (en) 2008-06-19 2008-06-19 Control module for a fuel cell system, fuel cell system with the control module and method for controlling a fuel cell system

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Citations (2)

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WO2006054565A2 (en) * 2004-11-17 2006-05-26 Nissan Motor Co., Ltd. Output limiting device for fuel cell
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US20070259227A1 (en) * 2004-04-07 2007-11-08 Yamaha Hatsudoki Kabushiki Kaisha Fuel Cell System and Control Method Therefor
WO2006054565A2 (en) * 2004-11-17 2006-05-26 Nissan Motor Co., Ltd. Output limiting device for fuel cell

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