Patent Publication Number: US-2022212549-A1

Title: Modular range extender system for an electrically driven motor vehicle, and electrically driven motor vehicle having a range extender

Description:
The present invention relates to a modular range extender system for an electrically driven motor vehicle, a circuit arrangement for a vehicle electrical system of an electrically driven motor vehicle with a predetermined variant of a range extender of the modular range extender system as well as an electrically driven motor vehicle with a circuit arrangement of this kind. 
     Electrically driven motor vehicles often still have a relatively limited range due to the current energy density of high-voltage batteries. In order to extend the range, it is known per se to use so-called range extenders in electric vehicles, in order to increase the range. The currently most frequently used range extenders have internal combustion engines, which drive a generator, which in turn supplies the high-voltage battery and/or the electrical drive machine electric motor with power. 
     In addition, range extenders are also known, which have a multiplicity of fuel cells. An advantage of said range extenders is that they are virtually emission-free, since hydrogen and oxygen usually react to form water. Normally, such range extenders based on fuel cells require one or more compressors, in order to supply the compressed air to the fuel cells. The compressors have to be adapted to the respective range extender in a relatively complex manner. In addition, the electrical interconnection of such range extenders based on fuel cells with a high-voltage battery is relatively expensive. 
     The object addressed by the present invention is therefore to provide a solution, by means of which range extenders based on fuel cells can be adapted particularly easily to different boundary conditions. 
     Said object is solved by the subjects of the independent claims. Further possible embodiments of the invention are indicated in the dependent claims. 
     The modular range extender system according to the invention for an electrically driven motor vehicle comprises a plurality of fuel cell basic modules, which each have a plurality of fuel cells connected in series and interfaces for supplying hydrogen and air as well as for discharging water and residual gas. Furthermore, the modular range extender system comprises a media supply device, which is designed to supply air and hydrogen to the fuel cell basic modules via the interfaces and to discharge water and residual gas from the fuel cell basic modules via the interfaces. In order to provide different outputs and/or voltages, different numbers of fuel cell basic modules are electrically connectable to one another in different series and/or parallel circuits and are configurable with the media supply device to form respective variants of a range extender. 
     It is essential in the modular range extender system that the individual fuel cell basic modules can be scaled by a corresponding combination as desired for each application case to form an overall system, therefore, a specific variant of a range extender. By means of a corresponding parallel circuit and series circuit of the individual fuel cell basic modules, different variants of a range extender can be configured, which differ, for example, with regard to the power that can be provided, but, for example, can provide the same high voltage. Of course, it is also possible that the fuel cell basic modules can be interconnected in such a way that the voltages that can be provided differ in the case of different variants of the range extender. 
     The fuel cell basic modules can also include a wide variety of peripheral and system components that are integrated into the respective fuel cell basic modules for a highly independent function of said fuel cell basic modules. In particular, it is possible, in a configuration correspondingly adapted to a respective boundary condition to achieve a particularly high service life and efficiency in the relevant variant of the range extender. This is possible, among other things, in that a design adapted to the boundary condition can be achieved with defined operating points of the relevant variant of the range extender. In particular, it is also possible to design the respective variants of the range extender for a partial load range. 
     In particular, it is possible by means of the modular range extender system according to the invention, to configure variants of a range extender adapted to respective boundary conditions on the basis of the fuel cell basic modules that can be produced relatively inexpensively. Thus, it is possible to configure and to build different variants of range extenders based on the fuel cell basic modules, which can differ virtually as desired in terms of their output and voltage level. 
     The individual fuel cell basic modules can, for example, have a reactive surface of approx. 100 cm 2  and approx. 80 fuel cells. Of course, it is also possible, to design the number and surface of the bipolar plates and the number of fuel cells differently. The fuel cells connected in series for each fuel cell basic module can, for example, provide an open circuit voltage of 80 V and a voltage of 48 V in full load operation. However, depending on the design of the fuel cell basic modules other open circuit voltages and other operating points are also possible. 
     By means of the modular range extender system it is possible, for example, to configure very different variants of a range extender based on fuel cells for very different vehicle types. Thus, for example, a particularly powerful variant of a range extender can be provided for an electrically driven utility vehicle, and it is also possible, for example, to configure a less powerful variant of a range extender for an electrically driven small car based on the same fuel cell basic modules. The individual fuel cell basic modules have to be developed, tested and released only once. Subsequently, said different variants of the range extender can be configured on the basis of the preferably standardised fuel cell basic modules. 
     In particular, on the basis of the modular range extender system it is possible to configure a range extender on a fuel cell basis for a specific electric vehicle, which can be connected in parallel to a high-voltage battery of the electric vehicle without interposition of a DC voltage converter. The usually rather expensive DC voltage converter can therefore be dispensed with. Indeed, the voltage level of the correspondingly configured range extender on the basis of the modular range extender system can be adapted very easily to the voltage level of the relevant high-voltage battery, simply by connecting the individual fuel cell basic modules appropriately to one another in series and parallel circuits. 
     A possible embodiment of the invention provides that the fuel cell basic modules all have the same structure with regard to their components. In particular, it is also possible that the fuel cell basic modules all have the same dimensions. The fuel cell basic modules can thus be produced in large quantities in a particularly cost-effective manner, since they all consist of the same preferably standardised components. 
     A further possible embodiment of the invention provides that the fuel cell basic modules have their own control, wherein said control can be run on a common hardware of a respective variant of the range extender. In particular, this should be understood to mean that a software of the control does not necessarily have to run on a hardware associated with the respective fuel cell basic module, but rather can also run as software, for example, as a subroutine within a main control, on a control unit of the range extender. This has the advantage that one is not restricted to each fuel cell basic module having to maintain the corresponding control hardware. Said own control can therefore be understood as software. The fuel cell basic modules can thus be very easily exchanged with one another, for example, in the event of a fault with replacement modules, therefore with other fuel cell basic modules that have not been installed up to now. For this purpose, the control, sensor system and/or software for controlling a fuel cell basic mode—or else a software of the higher-level overall system, therefore of the relevant range extender variant—do not have to be changed or adapted. 
     A further possible embodiment of the invention provides that the fuel cell basic modules are designed to provide in each case an output in the range of 2 to 8 kW. Depending on the properties of the membrane electrode units installed in the fuel cell basic modules, the output can be different for the same reactive surface of the fuel cell basic modules. The aim is for all fuel cell basic modules to provide at least substantially exactly the same output. As a result, the scaling or configuration of different variants of the range extender on the basis of the individual fuel cell basic modules is particularly simple, since they provide at least substantially the same output. Preferably, the fuel cell basic modules also all have the same voltage. 
     According to a further possible embodiment of the invention it is provided that the media supply device for each fuel cell basic module has a separate air compressor for providing air. In particular, if the fuel cell basic modules are all designed the same or all have the same structure, exactly the same air compressor can also be used for all fuel cell basic modules. Regardless of this, it is possible in particular to provide exactly the right air compressor suitable for the respective fuel cell basic modules, which air compressor is adapted to the conditions of the respective fuel cell basic module. An air compression system for a certain variant of the range extender can also be configured and assembled particularly easily with regard to the air compressor. Indeed, for a certain variant, just as many air compressors have to be provided as there are fuel cell basic modules that have to be interconnected. A respective complex and new design of an air compression device for different variants of range extenders can therefore be dispensed with. 
     A further possible embodiment of the invention provides that the media supply device has a central media supply channel for supplying air and hydrogen as well as for discharging water, residual gas and air for the fuel cell basic modules, wherein the fuel cell basic modules can be coupled to the media supply channel to the left and right of said media supply channel. In addition to air, the residual gas contains unused or unreacted hydrogen. By means of this standardised structure, the fuel cell basic modules can be easily connected to the media supply channel in the case of very different configurations of the fuel cell basic modules. The media supply channel has standardised interfaces for this purpose, which can interact with likewise standardised interfaces of the respective fuel cell basic modules. Thus, it is possible very easily to couple the respective fuel cell basic modules to the media supply channel to the left and right of said media supply channel. The modular range extender system can, for example, have one or also a plurality of variants of different housings, wherein the central media supply channel can be integrated into these housings. Depending on the configured variants of the relevant range extender, the suitable housing variant with the associated media supply can then be selected. The individual fuel cell basic modules then simply only have to be connected to the relevant media supply channel. 
     According to a further possible embodiment of the invention, it is provided that the basic modules in each case have a first end plate and a second end plate, which are arranged at opposite ends of the fuel cell basic modules and between which the respective fuel cells are arranged, wherein exclusively the first end plate has the interfaces for supplying air and hydrogen as well as for discharging water, residual gas and air. This makes possible a particularly compact design for the relevant variant of the configured range extender. In addition, all interfaces on the respective fuel cell basic modules can be kept relatively small, since these are exclusively integrated into the first end plate. 
     A further possible embodiment of the invention provides that within the fuel cell basic modules, the fuel cells are positioned in two cell stacks arranged next to one another and electrically connected in series with one another, which cell stacks have a common U-shaped media guide for air, hydrogen, water and residual gas, wherein the second end plate for each basic module has a directional diversion for the media guide from one to the other cell stack. By means of the two cell stacks arranged next to one another and the U-shaped media guide, a particularly compact and flat design is produced for the individual fuel cell basic modules. This compact and in particular short design promises a relatively good robustness against mechanical loads and in particular against vibrations. The short and compact design also enables a simpler manufacture, since the smaller the number of stacked fuel cells and thus the shorter the design, the less the effect of tolerances. In addition, a highly automated production of the fuel cell basic modules can also be realised. 
     The circuit arrangement according to the invention for a vehicle electrical system of an electrically driven motor vehicle comprises a predetermined variant of a range extender based on the modular range extender system according to the invention or a possible embodiment of the modular range extender system according to the invention, a high-voltage battery for supplying energy to an electric drive machine of the motor vehicle, wherein the high-voltage battery and the range extender are interconnected without a DC voltage converter in the form of a parallel circuit and the range extender is designed to charge the high-voltage battery. In addition, the circuit arrangement comprises a switching device for establishing and disconnecting an electrically conductive connection between the range extender and the high-voltage battery. The circuit arrangement according to the invention has the particular advantage that it is possible to dispense with a normally otherwise required DC voltage converter, which is a relatively expensive component. The variant of the range extender is thereby designed in such a way that, on the one hand, it can charge the high-voltage battery without any problems and, on the other hand, it can be operated in such a way that it is not damaged when the range extender is connected or switched on, in particular, respective membranes of the range extender are not damaged. Said switching device can, for example, be a MOSFET, a transistor or also a mechanical relay, wherein freewheeling diodes can also be provided as safety elements. 
     The electrically driven motor vehicle according to the invention comprises the circuit arrangement according to the invention or a possible embodiment of the circuit arrangement. 
     A possible embodiment of the electrically driven motor vehicle provides that respective air compressors of the range extender for providing air to the fuel cell basic modules are arranged at other points in the motor vehicle than the associated fuel cell basic modules. Thus, although the air compressors can therefore be assigned to the respective fuel cell basic modules, they do not have to be arranged locally directly on the fuel cell basic modules. This can have a very advantageous effect with regard to the existing installation space or the utilisation of the existing installation space. The respective air compressors can be arranged individually or also combined in groups at suitable points in the electrically driven motor vehicle, specifically precisely where the air compressors have enough space and can suck in ambient air as well as possible. The fuel cell basic modules can in turn be arranged, for example, combined at a particularly crash-favourable point in the motor vehicle, where they also have a positive effect, for example, on a low centre of gravity of motor vehicle. 
     Further possible advantages, features and embodiments of the invention are described by means of the following figures. The features and combinations of features mentioned above in the description and the features and combinations of features shown alone below in the figure description and/or in the figures can be used not only in the combination indicated in each case, but also in other combinations or alone, without leaving the scope of the invention. 
    
    
     
       The drawing shows in: 
         FIG. 1  a schematic perspective view of a fuel cell basic module, which has a plurality of fuel cells connected in series and to which a compressor for supplying air is assigned; 
         FIG. 2  a schematic representation of a plurality of fuel cell basic modules, which combined groups are connected in series, wherein some of said groups are in turn connected to one another in parallel; 
         FIG. 3  a schematic top view of a possible variant of a range extender, which has been configured on the basis of the individual fuel cell basic modules; 
         FIG. 4  a top view of one of the fuel cell basic modules, wherein a U-shaped media guide is depicted schematically; 
         FIG. 5  a highly schematised representation of a circuit arrangement for a vehicle electrical system of an electrically driven motor vehicle, which comprises a parallel circuit of a variant of a range extender and a high-voltage battery; and in 
         FIG. 6  a schematic representation of an electrically driven motor vehicle, which has a variant of the range extender composed of the fuel cell basic modules. 
     
    
    
     In the figures, identical or functionally identical elements have been provided with the same reference signs. 
     In  FIG. 1 , a fuel cell basic module  10  is depicted in a perspective view in a highly schematised manner. The fuel cell basic module  10  comprises a stack  12 , also called a stack, of a plurality of fuel cells connected in series and not described in further detail. The fuel cells comprise respective bipolar plates and respective so-called membrane electrode units. The fuel cell basic module  10  additionally comprises a first end plate  14  and a second end plate  16 , between which the stack  12  is arranged. 
     In addition, the fuel cell basic module  10  comprises a plurality of interfaces not shown here for supplying hydrogen and air as well as for discharging water and residual gas. It can thereby be provided that exclusively the first plate  14  forms a kind of plug-and-play front end, which has all interfaces. In addition, a compressor  18  is associated with the fuel cell basic module  10 , which is used to convey air and thus oxygen to the individual fuel cells. Contrary to the present representation, however, it is not required that the compressor  18  is arranged directly on the fuel cell basic module  10 . Instead, it can also be provided that the compressor  18  is arranged at a completely different point during installation in the relevant motor vehicle than the fuel cell basic module  10 . It must merely be ensured by means of a corresponding line or piping, that the compressor  18  can convey air and thus oxygen to the fuel cell basic module  10 . 
     In  FIG. 2 , a plurality of the fuel cell basic modules  10  are depicted. In order to provide different outputs and/or voltages, different numbers of fuel cell basic modules  10  can be electrically connected to one another in different series and/or parallel circuits and can be configured with a media supply device not shown here to form respective variants of a range extender. Said media supply device, not shown here, is designed to supply air and hydrogen via the mentioned interfaces of the respective fuel cell basic modules  10  and to discharge water and residual gas from the respective fuel cell basic modules  10  via the interfaces. 
     In the present case, several groups  19  of fuel cell basic modules  10  connected to one another in series are shown schematically. For example, so many of the fuel cell basic modules  10  are connected to one another in series for each group  19 , that these can provide a voltage of, for example, 480 V and an output of 24 kW. Another interconnection is of course also possible. By connecting the individual groups  19  in parallel, it is possible to increase the output that can be provided, while the voltage remains the same. In principle, any scaling of the output for each application case is possible by a corresponding interconnection of the individual fuel cell basic modules  10 . 
     The individual fuel cell basic modules  10  can have, for example, a reactive surface of approx. 100 cm 2  and 80 individual fuel cells. Other surfaces and numbers are also possible. Thus, for example, it is possible that the respective fuel cell basic modules  10  can provide an open circuit voltage of 80 V and a voltage of 48 V under full load, wherein the fuel cell basic modules  10  can be designed, for example, to provide an output in the range of 2 to 8 kW. Other voltages and outputs are also possible, in particular, depending on the selected or installed membrane electrode units in the individual fuel cell basic modules  10 . 
     In particular, it can be provided that the fuel cell basic modules  10  all have the same structure with regard to their components. The fuel cell basic modules  10  therefore form highly standardised units, in which the same components are installed everywhere. This enables high economies of scale to be achieved with correspondingly low purchasing and production costs. The individual fuel cell basic modules  10  as well as the media supply device mentioned therefore jointly form a modular range extender system  20 , wherein depending on the boundary condition or application case the standardised fuel cell basic modules  10  can be interconnected in a wide variety of configurations. In each case the fuel cell basic modules can have their own control, wherein said control can be run, for example, on a common hardware for a specific configured variant of a range extender. 
     In  FIG. 3 , a possible variant of a range extender  22  is shown in a highly schematised manner in a top view, which has been configured or assembled on the basis of the individual fuel cell basic modules  10 . Purely by way of example, the individual fuel cell basic modules  10  have all been connected to one another in series. A negative pole  24  and a positive pole  26  of the thus configured range extender  22  are indicated schematically. The respective fuel cell basic modules  10  are arranged in an enclosure  28 . The previously mentioned media supply device comprises a central media supply channel  30  for supplying air and hydrogen as well as for discharging water, residual gas and air for the respective fuel cell basic modules  10 . As can be seen, the individual fuel cell basic modules  10  are arranged to the left and right of the media supply channel  30  and coupled to the latter. For this purpose, the media supply channel  30  comprises interfaces not shown in detail, which can interact with the interfaces of the individual fuel cell basic modules  10  already mentioned above. 
     In  FIG. 4 , one of the fuel cell basic modules  10  installed in the range extender  22  is schematically depicted in a top view. Deviating from the embodiments shown in  FIGS. 1 and 2 , the fuel cells, not described in greater detail here, are positioned within this fuel cell basic module  10  in two cell stacks  32 ,  34  arranged next to one another and electrically connected in series. The fuel cell basic module  10  comprises an only schematically indicated U-shaped media guide  36  for air, hydrogen, water and residual gas, wherein the second end plate  16  has a directional diversion  38  for the media guide from one to the other cell stack  34 ,  32 . The first end plate  1  in turn has exclusively the interfaces, not depicted in detail here, for supplying air and hydrogen as well as for discharging water and residual gas. 
     This results in a particularly compact design of the fuel cell basic modules  10 . In particular, a particularly flat design and short design can thus be achieved for the range extender  22  configured on the basis of the thus designed fuel cell basic modules  10 . 
     In  FIG. 5 , a circuit arrangement  40  for a vehicle electrical system, not shown in more detail, of an electrically driven motor vehicle is depicted in a highly schematised manner. The circuit arrangement  40  comprises a predetermined variant of a range extender  22  based on said modular range extender system  20 . Furthermore, the circuit arrangement  40  comprises a high-voltage battery  42  for supplying energy to an electric drive machine  44  of the relevant motor vehicle. A frequency converter  46 , which is associated with the electric drive machine  44 , is also shown schematically. The high-voltage battery  42  and the range extender  22  are interconnected in the form of a parallel circuit without a DC voltage converter, wherein the range extender  22  is designed to charge the high-voltage battery  42 . 
     A circuit arrangement  48  for establishing and disconnecting an electrically conductive connection between the range extender  22  and the high-voltage battery  42  is also part of the circuit arrangement  40 . The switching device  48  can, for example, be a MOSFET, a transistor or also a mechanical relay. One or a plurality of freewheeling diodes  50  can also be provided as safety elements. Due to the fact that the circuit arrangement  40  does not have a DC voltage converter, installation space and corresponding costs can be saved. It can be ensured by a correspondingly suitable predictive regulation or control, that when the range extender  22  is switched on, it is nevertheless not damaged. 
     In  FIG. 6 , an electrically driven motor vehicle  52  is depicted in a highly schematised manner. A part of the circuit arrangement  40  is also shown schematically. Several of the previously mentioned air compressors  18  are also shown schematically. The air compressors  18  are assigned to the individual fuel cell basic modules  10  (not shown) of the relevant or configured variant of the range extender  22 . The air compressor  18  can convey sucked-in air to the individual fuel cell basic modules  10  via corresponding channels or lines. The air compressors  18  do not thereby—as already mentioned—have to be arranged directly on the fuel cell basic modules  10 . Instead, the air compressors  18  can be arranged at other suitable points in the motor vehicle  52 , in particular where the space conditions allow it particularly well and at the same time the ambient air can be sucked in particularly well by means of the air compressor  18 . 
     The individual fuel cell basic modules  10  can in turn be arranged with regard to a favourable vehicle centre of gravity and a favourable packaging at other points in the motor vehicle  52 . The individual air compressors  18  can be combined, for example, in the form of a compressor module. Depending on the configuration of the range extender  22  and above all depending on the number of fuel cell basic modules  10  installed therein, the number of air compressors  18  to be used can vary. The number of air compressors  18  thereby corresponds precisely to the number of fuel cell basic modules  10 . 
     LIST OF REFERENCE SIGNS 
     
         
           10  fuel cell basic module 
           12  stack of fuel cells connected in series 
           14  first end plate 
           16  second end plate 
           18  air compressor 
           19  groups of fuel cell basic modules connected in series 
           20  modular range extender system 
           22  variant of a range extender 
           24  negative pole of the range extender 
           26  positive pole of the range extender 
           28  enclosure of the range extender 
           30  central media supply channel 
           32  cell stack 
           34  cell stack 
           36  U-shaped media guide 
           38  directional diversion for the media guide 
           40  circuit arrangement 
           42  high-voltage battery 
           44  electrical drive machine 
           46  frequency converter 
           48  switching device 
           50  free-wheeling diode 
           52  motor vehicle