ELECTRICAL SYSTEM FOR A MOTOR VEHICLE AND METHOD FOR CONTROLLING THE SAME

Abstract

The present development relates to an electrical system (5) for a motor vehicle (1) comprising: - at least an electric drive (32) and - Fuel cell arrangement (20) comprising a first fuel cell (40) and a second fuel cell (42), which are of different dimensions and can be controlled and / or regulated independently of each other, - a control unit (50) designed to control or regulate the electrical power output of the first fuel cell (40) and the second fuel cell (42) depending on the current or predicted electrical energy consumption of the motor vehicle (1).

Description

Technical field

[0001] The present development relates to an electrical system for a motor vehicle and a method for controlling such an electrical system. Furthermore, the present development relates to a motor vehicle equipped with such an electrical system. background

[0002] Electric vehicles, i.e., vehicles where traction is predominantly or at least partially provided by an electric drive, must be supplied with sufficient electrical power. This can be achieved, for example, with a battery, such as a high-voltage battery.

[0003] However, batteries with sufficient storage and / or charging capacity are comparatively expensive and also contribute significantly to the overall weight of the vehicle.

[0004] To reduce the storage and / or charging capacity of such batteries, it is already known to generate a sufficiently high electrical power continuously or on demand, for example by means of a fuel cell, or to provide it for propulsion and / or for charging the high-voltage battery.

[0005] Conventional fuel cells are often unable to respond relatively quickly to changing electrical power demands from the vehicle's electrical system. Therefore, it is often necessary to provide a high-voltage battery as a buffer storage device.

[0006] Fuel cells require a relatively long time interval, especially during the start-up phase but also for a shutdown, in order to switch between a standby mode and a continuous power mode.

[0007] Against this background, it is desirable to increase the dynamics and performance of the electrical power of a fuel cell or fuel cell assembly in order to reduce the capacity of a buffer battery of the vehicle, for example for the purpose of cost and / or weight optimization. Advantageous designs

[0008] The described disadvantages and problems are eliminated or solved with an electrical system for a motor vehicle, with a motor vehicle, and by means of a method for controlling and / or regulating an electrical system according to the features of the independent patent claims.

[0009] In a first aspect, an electrical system for a motor vehicle is provided. The electrical system comprises at least an electric drive and a fuel cell assembly. The fuel cell assembly comprises a first fuel cell and a second fuel cell. The first fuel cell and the second fuel cell are of different dimensions. They can be controlled and / or regulated independently of each other.

[0010] The electrical system further includes a control unit designed to manage and / or regulate the electrical power output of the first and second fuel cells based on the vehicle's current or predicted electrical energy consumption. The vehicle's current or predicted electrical energy consumption can essentially be defined or determined by the current or future, i.e., predicted, power consumption of the electric drive.

[0011] Depending on the driving situation of the motor vehicle, for example when driving in city traffic, driving on expressways or motorways or driving on roads with inclines or declines, a wide variety of electrical power requirements arise from the electric drive.

[0012] With the fuel cell arrangement proposed here, comprising two differently dimensioned fuel cells, the motor vehicle, in particular the varying power requirements of the electric drive, can react relatively quickly and spontaneously and thus adequately to varying electrical power requirements.

[0013] Fuel cells of different sizes exhibit different characteristics in terms of their response, power dynamics, electrical power output, and thermal properties. A relatively small fuel cell, due to its comparatively small size and low power consumption, can be switched from standby mode to regular operating mode relatively quickly.

[0014] The thermal adaptability of a relatively small fuel cell is comparatively high; it is at least higher than that of a larger fuel cell. In other words, a relatively small fuel cell can be heated up to its operating temperature relatively quickly. It can be heated to an operating temperature level significantly faster and more efficiently with a given amount of thermal energy than a larger fuel cell.

[0015] In this respect, a comparatively small fuel cell can provide a significant amount of electrical power, particularly during a cold start phase of the electrical system or the motor vehicle, at a relatively early point in time, which can be used for traction of the motor vehicle or for operating various electrical consumers of the motor vehicle relatively early, i.e., already a short time after a start of the motor vehicle or the electrical system.

[0016] A relatively large fuel cell, due to its greater mass and larger geometric dimensions, exhibits a comparatively slow thermal adaptation. It requires a comparatively long time, or at least significantly longer than a smaller fuel cell, to transition from a cold initial state to a regular operating state at a predetermined operating temperature through warming or heating.

[0017] Nevertheless, a comparatively large fuel cell can provide higher electrical power during operation than a smaller one. Furthermore, a larger fuel cell can respond much more quickly to varying power demands, such as those of the vehicle's electrical system, during operation.

[0018] Because the electrical system, in particular its fuel cell arrangement, has two differently dimensioned and independently controllable and / or independently adjustable fuel cells, advantageous synergy effects can be achieved by combining the electrical power output of the first fuel cell and the second fuel cell in a wide variety of driving situations or operating states of the motor vehicle and its electrical system.

[0019] For example, during a cold start phase, the smaller fuel cell can provide a significant, or effectively usable, electrical power to the vehicle at an earlier point in time than the larger fuel cell, so that a significant electrical power can already be provided by the fuel cell arrangement in a relatively early phase within a cold start procedure of the vehicle.

[0020] For several load requirements encountered in practice, such as when the vehicle is driven only in city traffic at the beginning of a journey and during a cold start phase, electrical power generation or provision primarily by the smaller fuel cell may be sufficient. The smaller fuel cell can provide sufficient electrical power, particularly in a relatively early phase or shortly after the start-up phase of the fuel cell system, for example, to warm the larger fuel cell to a predetermined operating temperature level using an electric heater.

[0021] In this respect, the smaller fuel cell can be used to shorten the heating phase of the larger fuel cell to a predetermined operating temperature level, thus effectively shortening the overall heating phase of the fuel cell arrangement.

[0022] In other or further driving situations, such as when the current or predicted energy consumption of the vehicle suddenly changes, especially if, for example, the electrical power requirement for the fuel cell arrangement should increase abruptly due to the electric drive for acceleration of the vehicle and / or for driving at high speed, the larger dimensioned fuel cell can react without any significant delay, i.e., almost instantaneously, to the increased power requirement of the drive and / or the electrical system, or the electrical consumers of the vehicle, due to its shorter and comparatively prompt response time compared to the smaller fuel cell.

[0023] Such a rapid reaction or response would not be achievable with a comparatively small fuel cell.

[0024] By combining two fuel cells of different sizes, the electrical system can react much more dynamically to varying instantaneous and / or predicted electrical power demands of the drive system or the vehicle. Consequently, a buffer battery, such as a high-voltage battery, which can be coupled to the fuel cell array via a DC / DC converter, can have a smaller capacity compared to existing solutions or solutions with only one fuel cell. This can further reduce the battery's weight and thus the overall vehicle weight. Furthermore, the manufacturing costs for such a battery can be lowered.

[0025] It is even possible and conceivable, with appropriate design of the fuel cell arrangement, to completely dispense with a buffer battery if it is ensured that the combination of differently sized first and second fuel cells or, if necessary, further fuel cells with dimensions different from the first and second fuel cells, covers the current and / or predicted electrical energy consumption of the vehicle.

[0026] After further development of the electrical system, the control system is designed to control and / or regulate the electrical power of one of the first fuel cells and the second fuel cell depending on a current or predicted operating state of the other of the first and second fuel cells.

[0027] For example, if the first fuel cell is the one that is larger than the second fuel cell, it may be planned that during a cold start phase of the electrical system, for example when neither of the two fuel cells has a predetermined operating temperature, the second fuel cell should first be put into operation in order to heat the second fuel cell to a predetermined operating temperature level in this way and possibly using a comparatively small amount of thermal energy, at which the second fuel cell first generates electrical power that can then subsequently be used to heat or temper the first, larger fuel cell.

[0028] On the one hand, this increases the efficiency of the electrical system, since the thermal energy required to start up the fuel cell array only needs to be calculated based on the smaller fuel cell. Only after the second fuel cell is operational and providing usable electrical power can the first, i.e., the larger, fuel cell be started up successively. In this way, less primary energy needs to be supplied to the electrical system or the vehicle, for example, to heat up the fuel cell array and bring both fuel cells to a predetermined operating temperature.

[0029] According to a further embodiment, the control system can also be designed to control or regulate the electrical power of a first fuel cell and a second fuel cell, depending on a current or predicted operating state of the respective fuel cell.

[0030] In a further embodiment of the electrical system, the control system is designed to control and / or regulate the electrical power output of the first and second fuel cells in relation to the total power output of the fuel cell array, depending on a change or rate of change in the current or predicted electrical energy consumption of the vehicle. In particular, it may be provided that the proportion of the output of the first and second fuel cells to the total power output of the fuel cell array is controlled and / or regulated depending on a change or rate of change in the current or predicted electrical energy consumption of the vehicle, or adaptively adapted to the current or predicted total electrical energy consumption of the vehicle.

[0031] If, for example, the motor vehicle is on a highway or motorway and the operation of the motor vehicle requires a significant constant electrical power, which, for example, for efficiency reasons, is to be covered predominantly by the larger fuel cell, i.e. the first fuel cell, it may be possible to reduce the power of the second fuel cell and / or to put the second fuel cell into a standby mode.

[0032] In further embodiments or application examples, it may also be provided that, in the case of a constant significant power demand from the motor vehicle or the electric drive, the first fuel cell, i.e. the larger dimensioned fuel cell, is operated a predetermined amount below its maximum power, so that in case of need, for example in the case of a changing energy consumption of the motor vehicle, for example in particular in the case of a sudden or spontaneous increase in the electrical power demand of the motor vehicle, it is possible to act as quickly as possible by means of the comparatively short response time of the first fuel cell.

[0033] Reducing the power output of the larger fuel cell in these cases is also based on the fact that fuel cells operate most efficiently at a point below their maximum power output. Therefore, it is desirable, and provided the power requirement allows it, to operate both fuel cells as close as possible to their optimal efficiency point.

[0034] According to a further embodiment, the control system of the electrical system is designed to control and / or regulate the electrical power of the first and second fuel cells in relation to the total power of the fuel cell arrangement as a function of the instantaneous operating temperature of the first and / or second fuel cell. In particular, it can be provided that in a comparatively cold operating condition of the first and / or second fuel cell, the total power of the fuel cell arrangement is primarily supplied or provided by the smaller fuel cell.

[0035] If both fuel cells are at a predetermined operating temperature, the electrical power distribution between the first fuel cell and the second fuel cell can be regulated such that the total power of the fuel cell arrangement is predominantly or mainly supplied by the first, i.e., the larger, fuel cell. However, the first fuel cell is preferably operated at a power level that is a predetermined amount below its maximum power. In this way, the first fuel cell can react to a changing load requirement of the vehicle, in particular to an increase in the electrical load requirement of the vehicle or the electrical system, with virtually no delay.

[0036] Following a further refinement of the electrical system, the control system is also designed to primarily supply electrical power to the fuel cell array from the smaller fuel cell during the start-up phase. In this way, during a cold start phase of the electrical system or the vehicle, the smaller fuel cell can be brought into operation relatively quickly, so that usable electrical power can be provided by the smaller, i.e., the second, fuel cell shortly after the electrical system is started.

[0037] According to a further embodiment, the control system for the electrical system is designed, in response to an increase in the current or predicted electrical energy consumption of the vehicle, to primarily supply the electrical power of the fuel cell arrangement from the larger fuel cell, for example, the first fuel cell. Due to its size and dimensions, the larger fuel cell is better suited than the smaller fuel cell to respond to varying electrical load requirements.

[0038] In a kick-down situation, where the vehicle needs to accelerate immediately, the fuel cell system may be required to deliver increased electrical power within a very short time. A larger fuel cell, with its correspondingly short or comparatively instantaneous response time, can meet this increased power demand immediately.

[0039] Finally, a further aspect involves a motor vehicle comprising a vehicle body and a previously described electrical system. In this respect, all features, properties, and advantages described with regard to the electrical system also apply equally to the motor vehicle; and vice versa. The motor vehicle can be implemented, for example, as a passenger car, a van, a bus, or a commercial vehicle.

[0040] With further modification of the vehicle and / or its electrical system, the electrical system can also be designed entirely without a buffer battery. In this case, the electrical system, or the vehicle itself, can be designed without a high-voltage battery. The first fuel cell and the second fuel cell can then directly cover the varying power requirements of the vehicle's electrical consumers, such as the varying power requirements of at least one or more of the vehicle's electric drives.

[0041] A further aspect of this development includes a method for regulating and / or controlling, and thus operating, the electrical system of a motor vehicle. The electrical system comprises a fuel cell arrangement consisting of a first fuel cell and a second fuel cell. The first and second fuel cells are of different dimensions and can be controlled and / or regulated independently of each other.

[0042] The process includes the steps of determining the current or predicted electrical energy consumption of the vehicle. The process further includes controlling and / or regulating the electrical output of the first fuel cell and / or controlling and / or regulating the second fuel cell depending on the determined electrical energy consumption of the vehicle.

[0043] In this way, the system can react immediately to varying electrical energy consumption of the vehicle by appropriately regulating and / or controlling the first and second fuel cells. Due to their different dimensions, the first and second fuel cells have different response times and, consequently, different electrical and / or thermal response characteristics. Furthermore, due to their different dimensions, the first and second fuel cells also exhibit different thermal properties, particularly when heating up to an operating temperature.

[0044] The smaller fuel cell, such as the second fuel cell, can be heated to a predetermined operating temperature much faster and more efficiently, requiring less thermal energy, due to its smaller size or dimensions. Therefore, the second fuel cell is particularly suitable for relatively immediate operation of the fuel cell array during a cold start phase.

[0045] The first fuel cell, which can be larger than the second fuel cell, is particularly suitable, due to its shorter electrical response time, for reacting as quickly and as little time delay as possible to varying power requirements of the vehicle, especially increasing power requirements of at least one electric drive, when both fuel cells are in operation.

[0046] Naturally, both fuel cells can be operated simultaneously using a dedicated control system, for example to achieve maximum power output. Furthermore, the electrical output of each fuel cell can be variably and flexibly adapted to the respective driving situation, and thus to the vehicle's energy consumption.

[0047] The method is specifically designed and intended for regulating and / or controlling a previously described electrical system. Therefore, all features, advantages, and applications described with regard to the electrical system also apply equally to the method; and vice versa.

[0048] In a further embodiment of the method, the electrical output of the first and second fuel cells is controlled and / or regulated depending on the current or predicted operating state of the other fuel cell. For example, if both fuel cells are in standby mode and / or their operating temperatures are below a predetermined operating temperature level, the system may, for instance, prioritize the operation of the second fuel cell, which is smaller than the first, or draw electrical power primarily from the second fuel cell.For this purpose and during this time, it may be necessary to supply the second fuel cell with thermal energy until it reaches a predetermined operating temperature level at which the second fuel cell in question is able to provide usable electrical power.

[0049] In a further embodiment of the method, the electrical power of the first fuel cell and the second fuel cell is controlled or regulated with respect to the total power of the fuel cell arrangement as a function of a change or rate of change of the current or predicted electrical energy consumption of the motor vehicle.

[0050] This allows the power distribution between the first and second fuel cells, or rather the respective share of the total power output of the fuel cell array, to be controlled and / or regulated depending on the current or predicted electrical energy consumption of the vehicle. For example, if the vehicle is on a highway or expressway and the predicted total energy consumption is comparatively high, perhaps due to high-speed driving, the vehicle's electrical energy needs can be primarily met by the larger fuel cell.

[0051] If, however, maximum power is required, both fuel cells must naturally be operated at their maximum power level. Furthermore, it can be provided that, when the electrical power demand is between approximately 60% and 80% of the maximum power of the fuel cell array, the first fuel cell, which is larger than the second fuel cell, is continuously operated at a predetermined level below its maximum power. This allows for a spontaneous and, if possible, immediate response to any further increase in the vehicle's power demand. Brief description of the characters

[0052] Further objectives, features, and advantageous applications of the motor vehicle, its electrical system, and a method for controlling or regulating the electrical system are described in the following description of an exemplary embodiment with reference to the figures. These figures show: Fig. 1 a schematic representation of a motor vehicle equipped with a fuel cell, Fig. 2. A block diagram of the electrical system of the motor vehicle, Fig. 3 a block diagram of a fuel cell arrangement of the electrical system, Fig. 4. A flowchart of a process for controlling or regulating the electrical system or its fuel cell arrangement. Fig. 5 a performance diagram of two fuel cells during a cold start phase of the motor vehicle and Fig. 6 A performance diagram of two fuel cells during dynamic driving of the motor vehicle. Detailed description

[0053] The in Fig. 1. A schematically represented motor vehicle 1 has a vehicle body 2 and an interior 3 functioning as a passenger cell. The motor vehicle 1 is implemented as a fuel cell vehicle. It has an electrical system 5 with a fuel cell arrangement 20, which is in Fig. 2 is shown schematically.

[0054] The fuel cell assembly 20 is connected to a fuel storage device 22, for example, a hydrogen tank. Electrical energy can be generated by the fuel cell assembly 20 through an electrochemical reaction with the fuel supplied via the tank, for example, hydrogen. This energy can be supplied to a high-voltage battery 30 via a DC / DC converter 28. The high-voltage battery 30 can also provide electrical power for a drive 32, for example, an electric motor.

[0055] Furthermore, the high-voltage battery 30 can be connected to a high-voltage network 34 and supply it with electrical power. A low-voltage network or low-voltage system 26 can also be connected to the DC / DC converter, which can be supplied with electrical power via the DC / DC converter and ultimately by the high-voltage battery 30. Optionally, the electrical system 5 can include a charging unit 24, which allows, for example, the high-voltage battery 30 to be charged by connecting it to an external power grid.

[0056] The fuel cell arrangement 20 is also linked to a controller 50 via data transmission. The controller 50, i.e., a separate fuel cell controller, controls the operation of the fuel cell arrangement 20. The controller 50 allows the fuel cell arrangement or individual fuel cells thereof 40, 42 to be switched on and off as needed, thus enabling the operation of the fuel cell arrangement 20 in a power generation mode and the transition of the fuel cell arrangement 20 to a standby mode, for example, depending on the state of charge of the high-voltage battery 30.

[0057] Furthermore, the control unit 50 allows the respective output of both fuel cells to be controlled and / or regulated independently of each other.

[0058] If the high-voltage battery 30 has a comparatively high state of charge or is approaching a maximum permissible state of charge, the fuel cell arrangement 20 can be switched off as required or put into a sleep mode or a standby mode.

[0059] For example, fuel cell 40, which has the highest minimum power output, can be switched off first. Then both fuel cells can be switched off. It proves advantageous that the smaller fuel cell 42, which will be switched on again at a later time, can then be warmed up to its operating temperature more quickly.

[0060] The high-voltage network 34 or high-voltage system as well as the low-voltage system 26 can each have additional electrical consumers 21, 23 which can be supplied with electrical energy from the battery 30 or from the fuel cell arrangement 20 as required.

[0061] Electrical consumers 21, 23 include in particular an electric passenger compartment heater, an electric fuel cell preheater, an electric air conditioning system or an electric compressor.

[0062] During operation of the vehicle 1, particularly when driving downhill or during braking maneuvers, the electric drive 32 can also be operated in a so-called recuperation mode, in which electrical energy is recuperated during the braking process and fed back into the battery 30. Furthermore, by connecting the charging unit 24 to an external battery or an external grid, excess electrical energy, which can be generated, for example, by the operation of the fuel cell 20, can also be supplied to or fed into the external battery and / or the external grid. This enables so-called vehicle-to-grid (V2X) operation of the fuel cell arrangement 20.

[0063] In the block diagram of the Fig. Figure 3 shows an example of the fuel cell arrangement 20 provided here. The fuel cell arrangement 20 comprises a first fuel cell 40 and a second fuel cell 42. The fuel cells 40 and 42 are independently controllable, for example, by means of an electrical control unit 50. In particular, the electrical power of the fuel cells 40 and 42 can be controlled independently of each other by means of the electrical control unit 50. For this purpose, the supply of fuel, for example, the supply of hydrogen from a fuel tank 22 to the respective fuel cells 40 and 42, is to be regulated and / or controlled. For this purpose, the control unit 50 can be connected via data transmission to controllable valves 44 and 46, which, for example, are each in flow connection with the anode side of the respective fuel cell 40 or 42.

[0064] By regulating or controlling the valve 44, the fuel flow to the first fuel cell 40 can be regulated as needed. Similarly, the supply of fuel, for example hydrogen from the fuel tank 22 to the second fuel cell 42, can be controlled or regulated by means of the valve 46.

[0065] The electrical power generated by the respective fuel cells 40, 42 is fed into the DC / DC converter 28, from where the electrical power generated on board the vehicle can be distributed as needed to the individual electrical consumers 21, 23 and to the drive 32. The two fuel cells 40, 42 are also coupled on the cathode side to a compressor 48, for example, an air compressor. The supply of air or oxygen to the fuel cells 40, 42 can be varied by operating the compressor 48 accordingly. Furthermore, it is conceivable that additional control valves (not shown) are also arranged in the supply lines 45, 47, which extend from the compressor 48 to the respective fuel cells 40, 42, and which can likewise be controlled or actuated by the electrical control unit 50.

[0066] As in Fig. As only indicated in Figure 3, the first fuel cell 40 is larger than the second fuel cell 42. Due to the different dimensions of the fuel cells 40 and 42, different thermal and electrical properties result. In particular, the fuel cells 40 and 42 differ in their electrical power output and their electrical and thermal response behavior, for example, in achieving or maintaining a predetermined operating temperature level.

[0067] In the flowchart of the Fig. Figure 4 schematically shows a method for regulating and / or controlling the electrical system 5. In a first step 100, the current or predicted electrical energy consumption of the vehicle is determined. In step 102, the electrical power of the first fuel cell and / or second fuel cell is controlled or regulated as a function of the determined electrical energy consumption of the vehicle. In an optional intermediate step 104, this control or regulation of the two fuel cells 40, 42 can be carried out as a function of a current or predicted operating state of the first fuel cell 40 and / or second fuel cell 42.

[0068] For example, if the query in step 104 reveals that the first fuel cell 40 has an operating temperature below its specified operating temperature level, the control or regulation in step 102 can primarily target the control or regulation of the second fuel cell 42.

[0069] Meanwhile, i.e., while the electrical power of the entire fuel cell arrangement 20 is predominantly or exclusively supplied by the second fuel cell 42, the first fuel cell 40 can be heated to the predetermined operating temperature level, for example, by electrical energy supplied by the two fuel cells 42. Subsequently, depending on and / or taking into account the operating temperature level of the first fuel cell 40 and / or the second fuel cell 42, the electrical power distribution between the first fuel cell 40 and the second fuel cell 42 can be regulated or adjusted according to demand, i.e., taking into account the current or predicted electrical energy consumption of the vehicle.

[0070] Steps 100 and 102 and the optional intermediate step 104 can be continuously repeated in a loop during the operation of electrical system 5 and can be performed repeatedly according to a predetermined timing.

[0071] In the two performance diagrams at the Fig. 5 and Fig. Figure 6 shows two exemplary operating modes of the electrical system 5. In both diagrams 200 and 300, the electrical power of the electrical system 5 and the fuel cell arrangement 20, respectively, is shown over time. Fig. 5 reflects a cold start phase of the electrical system 5, or of the motor vehicle 1.

[0072] Graph 202 represents the power requirement of the motor vehicle, and thus the required electrical energy consumption of the motor vehicle. Graph 204 represents the electrical power, and thus the electrical power output of the first fuel cell 40. Graph 206 reflects the corresponding electrical power of the second fuel cell 42, and graph 208 indicates the total power of the fuel cell arrangement 20.

[0073] Due to the smaller dimensions of the second fuel cell 42 compared to the first fuel cell 40, during the cold start phase of the system, i.e., at times before time t1, it is intended that the total power 208 of the fuel cell arrangement 20 is initially or predominantly supplied by the power 206 of the second fuel cell 42. This allows the second fuel cell to be heated up to an operating temperature level relatively quickly during the cold start phase and thus provide usable electrical power after only a short time.

[0074] The warm-up time or warm-up phase of the larger fuel cell 40 is considerably longer. It can only deliver a significant electrical output sufficient to meet the energy demand of the vehicle, together with the second fuel cell 42, at time t1. Nevertheless, by providing the first and second fuel cells 40, 42, the fuel cell arrangement 20 can deliver a total electrical output 208 well before time t1 is reached, which is significantly greater than the output 204 available from the first fuel cell 40. In this respect, the fuel cell arrangement 20 can respond to the electrical power demand 202 of the vehicle 1 relatively early by means of the smaller fuel cell 42.

[0075] In Fig. 6 is one of the Fig.Figure 5 shows a fundamentally comparable power-time diagram. Here, both fuel cells 40 and 42 are already at the required operating temperature. Up to time t1, the vehicle 1, or rather the electrical system 5, demands a comparatively low or almost no power. At time t1, however, the electrical energy consumption, or rather the electrical power demand 302 of the vehicle 1, increases abruptly. This abrupt increase causes the first fuel cell 40 to react relatively quickly due to its shorter response time and to provide a sharply increasing electrical power output 304. The electrical response time of the second fuel cell 42 is significantly longer. To meet the power demand, the power output 306 of the second fuel cell 42 is also steadily increased in the time interval between t1 and t3.

[0076] At time t2, which lies between times t1 and t3, the total power 308 of the fuel cell arrangement matches the power requirement 302 of the vehicle. To maintain the electrical power 308 of the entire fuel cell arrangement 20, it is now provided in the time interval between t2 and t3 that the electrical power 304 of the first fuel cell 40 is slightly reduced and that this reduction is essentially compensated for by an increase in the power 306 of the second fuel cell 42.

[0077] In this way, it can be achieved that at time t3 both fuel cells 40, 42 are operated in a medium power range, which is a predetermined amount below the maximum power of the respective fuel cell 40, 42.

[0078] Reducing the power output of the larger fuel cell 40 in these cases and replacing it with the power output of the smaller fuel cell 42 is also based on the fact that fuel cells can be operated most efficiently at a point below their maximum power output. Therefore, if the power requirement allows, the aim is to operate both fuel cells 40 and 42 as close as possible to their optimal efficiency point.

[0079] In the time interval between t3 and t4, the power demand 302 of the vehicle 1 decreases. Both fuel cells 40 and 42 can react directly and immediately to this reduced power demand by means of a corresponding reduction in power output. At time t4, the power demand 302 increases again. The power demand of the vehicle 1 rises here, specifically to the maximum power output 310.

[0080] As illustrated in the period between t4 and t5, the first fuel cell 40 can again respond immediately to the increased power demand due to its shorter electrical response time. At time t5, both fuel cells 40 and 42 can finally deliver their maximum power to fully provide the required maximum power to the fuel cell array 20.

[0081] The illustrated embodiments merely show possible configurations of the development, for which numerous further variants are conceivable during development. The exemplary embodiments shown are in no way to be interpreted as limiting with regard to the scope, applicability, or configuration possibilities of the development. The present description merely shows the person skilled in the art one or a few possible implementation(s) of an embodiment. Thus, a wide variety of modifications can be made to the function and arrangement of the described elements without departing from the scope of protection defined by the following claims or their equivalents. Reference symbol list 1 motor vehicle 2 Motor vehicle body 3 Interior 5 electrical system 20 Fuel cell arrangement 21 consumers 22 fuel storage 23 consumers 24 charging units 26 Low-voltage system 28 DC / DC converters 30 high-voltage battery 32 Drive 34 High-voltage network 40 Fuel cell 42 Fuel cell 44 valve 45 Supply line 46 valve 47 Supply line 48 Compressor 50 Control

Claims

[1] Electrical system (5) for a motor vehicle (1) comprising: - at least an electric drive (32) and - Fuel cell arrangement (20) comprising a first fuel cell (40) and a second fuel cell (42), which are of different dimensions and can be controlled and / or regulated independently of each other, - a control unit (50) designed to control or regulate the electrical power output of the first fuel cell (40) and the second fuel cell (42) depending on the current or predicted electrical energy consumption of the motor vehicle (1). [2] Electrical system (5) according to claim 1, wherein the control (50) is configured to control or regulate the electrical power of one of the first fuel cell (40) and the second fuel cell (42) depending on an instantaneous or predicted operating state of the other of the first fuel cell (40) and the second fuel cell (42). [3] Electrical system (5) according to one of the preceding claims, wherein the control (50) is configured to control or regulate an electrical power of first fuel cell (40) and second fuel cell (42) with respect to a total power of the fuel cell arrangement (20) depending on a change or rate of change of the instantaneous or predicted electrical energy consumption of the motor vehicle (1). [4] Electrical system (5) according to one of the preceding claims, wherein the control (50) is configured to control or regulate an electrical power of first fuel cell (40) and second fuel cell (42) with respect to a total power of the fuel cell arrangement (20) as a function of an instantaneous operating temperature of first fuel cell (40) and / or second fuel cell (42). [5] Electrical system (5) according to claim 4, wherein the control (50) is configured to supply electrical power to the fuel cell arrangement (20) primarily from the smaller dimensioned fuel cell (42) during a start-up phase of the fuel cell arrangement (20). [6] Electrical system (5) according to one of the preceding claims, wherein the control (50) is configured to supply the electrical power of the fuel cell arrangement (20) primarily from the larger dimensioned fuel cell (40) in response to an increase in the instantaneous or predicted electrical energy consumption of the motor vehicle (1). [7] Motor vehicle (1) comprising: - a motor vehicle body (2) and - an electrical system (5) according to any one of the preceding claims. [8] Method for controlling and / or regulating an electrical system (5) of a motor vehicle (1), wherein the electrical system comprises a fuel cell arrangement (20) comprising a first fuel cell (40) and a second fuel cell (42) which are of different dimensions and can be controlled and / or regulated independently of each other, wherein the method comprises the following steps: - Determination of the current or predicted electrical energy consumption of the motor vehicle (1), - Controlling and / or regulating the electrical power of the first fuel cell (40) and / or the second fuel cell (42) depending on the determined electrical energy consumption of the motor vehicle (1). [9] Method according to claim 8, wherein the electrical power of one of the first fuel cell (40) and the second fuel cell (42) is controlled and / or regulated depending on an instantaneous or predicted operating state of the other of the first fuel cell (40) and the second fuel cell (42). [10] Method according to claim 8 or 9, wherein an electrical power of first fuel cell (40) and second fuel cell (42) is controlled and / or regulated with respect to a total power of the fuel cell arrangement (20) depending on a change or rate of change of the instantaneous or predicted electrical energy consumption of the motor vehicle (1).

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