Patent Application
20230173951
This application claims priority to German Patent Application No. DE 10 2021 213 977.9, filed on Dec. 8, 2021, the contents of which is hereby incorporated by reference in its entirety.
The invention relates to a method for operating a fuel cell system. In addition, the invention relates to a computer programme product and to a fuel cell system integrated in a motor vehicle.
A generic method is known from DE 10 2017 007 633 A1, according to which for operating a fuel cell of a motor vehicle it is provided to satisfy a specified requirement of drive power of a traction drive of the motor vehicle primarily by primary power, which is provided by a fuel cell of the motor vehicle. Because of the chemical operation of the fuel cell, providing the primary power however is relatively sluggish and lags the actual requirement of drive power, so that a power differential between the provided primary power and the specified requirement of drive power, which in practice is also referred to as power jump, has to be covered by additional power. This additional power referred to as secondary power is provided by a rechargeable traction battery of the motor vehicle. In order to prevent unfavourable operating ranges of the fuel cell caused by load peaks, DE 10 2017 007 633 A1 proposes to complement the dependency of the provision of primary power on the required drive power by a variable damping. By way of this, severe sudden changes of the required drive power can merely affect the provision of primary power or the operation of the fuel cell in a dampened manner. Disadvantageous in this actually elegant solution is that a delay in the response time of the fuel cell results in particular operating situations of the motor vehicle, for example start-up situations or emergency braking situations, a delay in the response time of the fuel cell results, which is not desirable in particular in these special operating situations of the motor vehicle.
The object of the invention lies in stating for a method for operating a fuel cell system an embodiment that is improved or at least different compared with the state of the art.
In the present invention, this object is solved through the subject matter of the independent claim(s). Advantageous embodiments are the subject matter of the dependent claim(s) and of the description.
The basic idea of the invention lies in operating the at least one fuel cell in a specified, energy-efficient operating range.
To this end, the invention proposes a method for operating a fuel cell system, with which the fuel cell system is provided at least with a fuel cell generating electric primary power, at least one rechargeable traction battery providing an electric secondary power, at least one traction drive and a power management device with which the at least one fuel cell, the at least one traction battery and the at least one traction drive are electrically coupled. It is substantial that the at least one fuel cell is profile-controlled.
This has the effect that the at least one fuel cell generates and provides electric primary power in a profile-controlled manner. In the process, the profile control can practically be dependent on the charge status of the battery. Further practically, the profile control can be varied or adapted as a function of the charge status of the traction battery. Further practically, the profile control can be varied or shifted as a function of the charge status of the traction battery so that the fuel cell either provides a relatively high amount of primary power, as a result of which a charge status of the at least one traction battery raised with respect to a mean charge status of the at least one traction battery is achieved, or provides a relatively low amount of primary power, as a result of which a charge status of the at least one traction battery that is lowered with respect to a mean charge status of the at least one traction battery is achieved. This has the advantage that undesirable operating ranges of the fuel cell, for example load peaks, are largely avoided. This has the positive effect that the at least one fuel cell consumes relatively few consumables. Further, it generates a constant lost heat flow free of load peaks which in terms of cooling, can be comparatively easily controlled and for example dissipated by means of a cooling system of the fuel cell system employed for cooling the at least one fuel cell.
Practically, the at least one fuel cell is profile-controlled dependent on a drive power and/or as a function of a charge status of the at least one traction battery. The operation of the at least one fuel cell or the provision of primary power can thus be coupled to a specified drive power to be provided by at least one traction drive and/or to a charge status of the at least one traction battery. Because of this, the at least one fuel cell can be operated so that an acceptable power jump results, i.e. an acceptable amount of secondary power has to be provided. This has the advantage that a desired target charge status of the traction battery can be achieved and/or maintained. Further, it can be operated in an energy-efficient operating range, in particular in a mean power range with optimal efficiency.
Practically, the invention interprets the term “profile-controlled” or “profile control” in a relatively wide sense, namely both in the sense of an open loop control and also in the sense of a closed loop control. Accordingly, profile-controlled can either mean an open loop profile control or a closed loop profile control.
Further practically it can be provided that the at least one fuel cell is profile-controlled so that it provides electric primary power as a function of a fuel cell profile referred to as FCBK in the following. Practically, the FCBK describes the functional relationship between the requirement of drive power and the primary power and/or secondary power to be provided by the fuel cell system for this purpose. The FCBK is practically dependent on a drive power and/or dependent on a charge status of the at least one traction battery. The FCBK is practically realised through a linear function or a non-linear function or a series of interpolable support points. The FCBK has practically a positive slope at least in portions, so that for small drive powers to be provided by at least one traction drive, small amounts of electric primary power and for growing drive powers to be provided, likewise growing larger amounts of electric primary power are generated and provided. Practically, the FCBK has a slope of zero at least in portions, so that in a diagram, in which drive powers to be provided are plotted over the provided primary powers, it forms a horizontal at least in portions.
Furthermore it can be provided that electric drive power, which is requested out of a power range extending from a no-load power to a full-load power of the at least one traction drive, is at least proportionally provided by the provided electric primary power. Here, a power differential (power jump) between the requested electric drive power and the provided electric primary power can be provided by electric secondary power, so that the requested electric drive power in total is composed of electric primary power and/or of electric secondary power. Because of this, at least one amount of the power required for providing the requested drive power is supplied by the at least one traction battery. By way of this, a certain relief of the at least one fuel cell and its cooling can be achieved. By way of the FCBK or the profile control of the at least one fuel cell, each requested drive power out of the said power range is assigned a specified composition ratio of electric primary power to electric secondary power. By way of this, the at least one fuel cell can be relatively easily operated within preferred operating ranges, so that in particular power peaks and excessively high operating temperatures accompanied by this can be avoided on the at least one fuel cell.
Furthermore, the primary power generated by the at least one fuel cell can be provided on the power management device and by means of the same, distributed to suit requirement to the at least one traction drive for providing a drive power and/or to the at least one traction battery for recharging the same. Optionally it can be provided that the profile control of the at least one fuel cell is carried out by the power management device. This means that the power management device carries out an open loop control or a closed loop control of the at least one fuel cell.
It is practical, furthermore, when the FCBK in a first power section of the said power range is provided by a straight line with constant, specifiable slope and with specifiable zero point offset. Because of this, the at least one fuel cell can be controlled within the first power section dependent on a drive power in such a manner that it provides electric primary power which is composed of a constant basic amount of primary power of electric primary power specified by the zero point offset and of an additional amount of primary power for growing drive powers to be provided likewise growing proportionally according to the specified slope of the straight line. Here, the said slope of the straight line can be positive so that the FCBK constantly increases over the said first power section which if applicable extends completely from a no-load power of the traction drive up to a full-load power of the traction drive. It is also conceivable that the said slope of the straight line is zero, in a pure range extender operation, i.e. the primary power provided by the fuel cell is dependent only on the charge status of the at least one traction battery, not on the requested drive power. In summary, constant electric primary powers likewise growing or a range extender operation can thus be provided within the first power section for growing, requested electric drive powers. Although for relatively high drive powers to be provided the amount of the drive power to be provided increases by way of this, which drive power is provided by electric primary power, but not to the same extent as the drive powers. By way of this, the amount to be provided by electric secondary power increases or diminishes at the same time. Conversely, the amount of the drive power to be provided for relatively low drive powers to be provided, which is provided by electric primary power, decreases, however likewise to a lesser extent than the drive power. By way of this, the amount to be provided by electric secondary power decreases. Because of this, the at least one fuel cell can be saved and operated in preferred operating ranges even with relatively low drive powers to be provided. For example, with relatively low drive powers to be provided (including no-load power), the at least one fuel cell can generate a certain base of electric primary power, which can be utilised for example for charging the at least one traction battery.
The said power range of at least one traction drive extends from a no-load power to a full-load power, in other words, it constitutes the power capacity of a traction drive. It can be practically standardised to a value range between 0 and 1 (0% and 100%). Additionally considering recuperation as well, the value range expands to negative values. What has been said can also be extrapolated into the negative range in this case. For example, the fuel cell can be continued to be operated with reduced power with increasing recuperation operation, as a result of which the traction battery on the one hand is charged by the power provided by the recuperation and on the other hand by the primary power provided by the fuel cell.
In other words, the said basic amount of primary power practically describes a base of electric primary power which is generated and provided by the at least one fuel cell in particular in the no-load mode. It can be specified by the said zero point offset, i.e. again in other words, by a shift of the FCBK, so that the at least one fuel cell generates and provides more or less electric primary power. The said additional amount of primary power is practically a variable amount of the electric primary power dependent on power and/or on a charge status of the at least one traction battery. Basic amount of primary power and additional amount of primary power together can form the electric primary power generated and provided by the at least one fuel cell in total.
Further it is practical when the first power section extends over the power range completely or at least in portions. Alternatively it can be provided that the first power section extends above a first specified power threshold and/or below a second specified power threshold. Here it can be useful when the first power threshold is variably adjustable over the entire power section; optionally it amounts to 30% of the full-load power. Further, the second power threshold can also be variably adjustable over the entire power section, and optionally it corresponds to 70% of the full-load power. It is obvious that values deviating upwards or downwards can also be selected. However, the second power threshold is practically always greater or equal to the first power threshold. Furthermore, the electric primary power can be provided with a basic amount of primary power of zero or greater than zero. By way of this, preferred ranges for the first power section are stated.
In order to be able to generate and provide adequate electric primary power and if applicable excess power for recharging the at least one traction battery by means of the at least one fuel cell, it can be provided, furthermore, that the specified basic amount of primary power is dependent on a charge status of the at least one traction battery. Alternatively or additionally it can be provided that a charge status of the at least one traction battery, raised with respect to the said charge status of the at least one traction battery, is achieved by increasing the specified basic amount of primary power. Conversely, it can also be provided that a charge status of the at least one traction battery that is lowered with respect to the said charge status of the at least one traction battery is achieved by reducing the specified basic amount of primary power.
Furthermore, the at least one fuel cell can be profile-controlled by means of the FCBK dependent on a drive power and/or dependent on a charge status of the at least one traction battery so that, in the event that the at least one traction drive is operated with a no-load power, it generates and provides a specified base of electric primary power referred to as basic amount of primary power deviating from zero. By way of this, the at least one fuel cell is then operated in a preferred operating range even when the at least one traction drive is in the no-load mode or switched off and the requested electric drive power is thus practically zero or zero. In other words, the fuel cell, by way of this, is operated with a basic utilisation, in the case of which a certain measure of electric primary power is provided permanently or for as long as the fuel cell system is active. Initially this has the advantage that even with the at least one traction drive at no-load, a certain base of accessible primary power is available, so that for example in a particular operating situation of a motor vehicle, for example a start-up situation, merely the remaining power differential has to be covered by electric secondary power. This results in a noticeable (measurable) relief of the at least one traction battery. Furthermore, the electric primary power (basic amount of primary power) generated with the at least one traction drive at no-load can be utilised for example for recharging the at least one traction battery, so that a specified charge status of the same can be retained.
In order to be able to depict different load statuses of the at least one traction battery, it can be practical when the specified basic amount of primary power is dependent on a specified (mean) load status of the at least one traction battery and/or on a differential of different load statuses of the at least one traction battery. In the process, a load status of the at least one traction battery, raised with respect to the specified (mean) load status of the at least one traction battery, can be achieved by increasing the specified basic amount of primary power. Conversely, a load status of the at least one traction battery lowered with respect to the specified (mean) load status of the at least one traction battery can be achieved by reducing the specified basic amount of primary power.
It is practical, further, when the FCBK, in a second power section of the said power range extending below a or the said first power threshold has the value zero or substantially the value zero. By way of this, the at least one fuel cell can be profile-controlled within the second power section so that it does not generate and provide any or practically no electric primary power. In the process, the first power threshold value can be variably adjustable over the entire power section; optionally it amounts to 30% of the full load power. This describes a capping range, within which the at least one fuel cell provides a constant amount (here zero or practically zero) of electric primary power, the same quasi independently of the actually requested drive power.
It is also practical when the FCBK has a constant maximum value in a third power section of the said power range extending above a second power threshold value. By way of this, the at least one fuel cell can be profile-controlled within the third power section so that it provides a maximally providable amount of primary power of electric primary power. In the process, the second power threshold value can be preferably variably adjustable over the entire power section, but optionally corresponds to 70% of the full load power of the at least one traction drive. This describes a further capping range within which the at least one fuel cell provides a constant amount (here greater than zero, preferably 100% of the electric primary power that can be provided by the at least one fuel cell) of electric primary power, and this quasi regardless of the actually requested drive power.
Furthermore it can be provided that the FCBK is dependent on a load status of the at least one traction battery. By way of this, electric primary power can be provided dependent on the battery charge status. Alternatively or additionally, the FCBK can be dependent on an ambient temperature of the fuel cell system, so that electric primary power is also provided dependent on temperature. Further alternatively or additionally, the FCBK can also be dependent on a battery production age of at least one traction battery, so that dependent on the battery status electric primary power is provided. Further, it can be alternatively or additionally provided that the FCBK is dependent on a battery charge cycle number of at least one traction battery, so that dependent on the battery status electric primary power is provided. It can also be practical when the FCBK is alternatively or additionally dependent on a fuel cell coolant temperature of at least one fuel cell, so that dependent on the fuel cell status electric primary power is provided. Further it is conceivable that the FCBK is alternatively or additionally dependent on a battery coolant temperature of at least one traction battery, so that dependent on the battery status electric primary power is provided. By way of this, the profile control of the at least one fuel cell is dependent on further variables relevant to the fuel cell system, so that the operation of the fuel cell can also take into account these variables.
Practically it can be provided that the traction battery is charged by means of the electric primary power provided by at least one fuel cell in the case that the requested drive power is smaller in the amount than the electric primary power provided by the fuel cell at this time. By way of this, the at least one traction battery can be recharged again in the case of an excess of electric primary power generated by the at least one fuel cell which is conceivable for example upon a sudden load change on at least one traction drive.
A further basic idea that can be realised additionally or alternatively to the above basic idea lies in stating a computer programme product which, when the programme or programme product is executed by a computer or a vehicle computer of a motor vehicle, in particular a power management device, prompts the same to carry out the method described above. Such a computer programme product can be implemented for example in a power management device of a fuel cell system in order to carry out the method described above in a fuel cell system. Practically, the computer programme product can also be implemented in a vehicle computer of a motor vehicle, which can practically form a part of a power management device of a fuel cell system of a motor vehicle.
Another further basic idea that can be realised additionally or alternatively to the above basic ideas lies in stating a fuel cell system integrated in a motor vehicle which is equipped at least with a rechargeable traction battery providing electric secondary power, at least one traction drive and a power management device with which the at least one fuel cell, the at least one traction battery and the at least one traction drive is electrically coupled. The said power management device is practically equipped in order to execute the computer programme product described above and/or carry out the method described above. By way of this, a preferred implementation of the method described above in a power management device of a fuel cell system of a motor vehicle is stated. Hence, the motor vehicle is quasi equipped in order to use the above method.
In summary it remains to note: the present invention preferentially relates to a method for operating a fuel cell system, in the case of which the fuel cell system is provided with a fuel cell generating electric primary power, at least one rechargeable traction battery providing electric secondary power, at least one traction drive and a power management device, with which the at least one fuel cell, the at least one traction battery and the at least one traction drive are electrically coupled, the at least one fuel cell being profile-controlled. In addition, the invention practically relates to a computer programme product comprising commands, which, when the programme is executed by a computer or a vehicle computer of a motor vehicle, causes the same to carry out the above method. In addition, the invention further practically relates to a fuel cell system integrated in a motor vehicle for carrying out the above method.
Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description by way of the drawings.
It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated, but also in other combinations or by themselves without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference numbers relate to same or similar or functionally same components.
It shows, in each case schematically:
The diagram shown in
Since the drive power 9, if applicable, is only covered at least proportionally by the electric primary power 2 generated and provided by the fuel cell 3 it is provided that a power differential 14 between the electric drive power 9 and the actually provided electric primary power 2 is provided by electric secondary power 4. By way of this, the electric drive power 9, at least in the case that the fuel cell 3 does not provide the entire requested electric drive power 9, is composed of electric primary power 2 and of electric secondary power 4.
In
The diagram shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 213 977.9 | Dec 2021 | DE | national |
