Electrical energy supply system and electric drive train having a fuel cell system and a generator connected in series

Abstract

The electrical energy supply system includes a fuel cell system having at least one fuel cell and having a first voltage output for providing a first voltage supplyable by the fuel cell system, and at least one electrical generator, each having a second voltage output for providing an associated second voltage generated by an associated generator. In an electrical interconnection situation, the first voltage output is connected in series or parallel to at least one of the second voltage outputs to provide a supply voltage present across the series or parallel circuit for providing electrical energy that can be produced by the energy supply system. The fuel cell system includes a plurality of fuel cell stacks, each in the form of an assembly, at least two of which are connected in series to provide an output voltage present across the series circuit for providing electrical energy that can be produced by the energy supply system. The electric drivetrain can include an energy supply system for supplying electrical energy to the electric drivetrain.

Description

[Technical Field]

[0001] The present invention relates in particular to an electric energy supply system for autonomous energy supply of an electric vehicle drive, as well as an electric drive train for a vehicle equipped therewith. The vehicle may in particular be a motor vehicle, in particular a truck or a passenger car. The aforementioned vehicle drive may therefore in particular be a drive for such a vehicle. In addition to motor vehicles, electrically powered construction vehicles, ships, or rail vehicles are also potential applications. The present invention can also be used in stationary applications. [Background technology]

[0002] Fuel cell systems (FCS) are known as a method for providing an energy supply system for providing electrical energy by electrochemical means. In particular, the use of fuel cell systems for environmentally friendly electrical energy supply of electric drives in electric or hybrid vehicles has long been known as a possibility and is already being implemented to some extent by various vehicle manufacturers. Stationary fuel cell systems for environmentally friendly local energy generation, for example to supply buildings or other infrastructure, are also known.

[0003] Furthermore, battery-based electric energy supply systems are also known, in particular those based on lithium-ion accumulators, which are mainly used as energy storage devices in today's electric or hybrid vehicles (battery electric vehicles (BEVs), or hybrid electric vehicles (HEVs), or plug-in hybrid electric vehicles (PHEVs)). Summary of the Invention [Problem to be solved by the invention]

[0004] It is an object of the present invention to provide an improved fuel cell-based energy supply system with high efficiency and / or high voltage stability, as well as an electric drivetrain for an electric vehicle equipped therewith. [Means for solving the problem]

[0005] This object is achieved according to the teaching of the independent claims. Various embodiments and developments of the invention are the subject of the dependent claims.

[0006] A first aspect of the solution presented herein relates to an electric energy supply system, in particular a system for the autonomous energy supply of an electrically driven vehicle drive (e.g. an automobile drive). The energy supply system comprises: (i) a fuel cell system having at least one fuel cell, the fuel cell system having a first voltage output for providing a first voltage deliverable by the fuel cell system; (ii) at least one electrical generator, each having a second voltage output for providing an associated second electrical voltage generated by the associated generator; Includes:

[0007] In an electrical interconnection situation, the first voltage output is connected in series or parallel to at least one of the second voltage outputs to provide a supply voltage present across the series or parallel circuit to provide electrical energy that can be produced by the energy supply system.

[0008] The circuit may optionally include additional circuit elements (such as ohmic resistors, diodes, or transistors). Within the circuit, particularly in series, the first and second voltage outputs may be connected directly to each other or with one or more other circuit elements connected therebetween.

[0009] A fuel cell system includes a plurality of fuel cell stacks, each designed as an assembly, at least two of which are connected in series to provide an electrical output voltage present across this series circuit to provide electrical energy that can be produced by an energy supply system.

[0010] The term "fuel cell system" (FCS) as used herein is understood to mean a system having at least one fuel cell for supplying electrical energy, in particular of the polymer electrolyte membrane (PEM) type. This system comprises a plurality of interconnected fuel cells, in particular a so-called fuel cell stack (or "stack" for short), where the associated fuel cells are usually connected in series to increase the voltage. A fuel cell system may also include other components necessary for the operation of the fuel cell(s). Such components may be used in particular for providing, storing, and / or processing the media necessary for the operation of the fuel cell(s) (e.g., hydrogen or methanol as fuel, on the one hand, and oxygen or air for the oxidation of the fuel in the context of the electrochemical reaction occurring in the fuel cell, on the other hand). Electrical energy converters, such as DC / AC converters, may also be used as components of an FCS.

[0011] As used herein, the term "electrical generator" or "generator" for short refers to an electric machine that converts kinetic energy into electrical energy, typically using electromagnetic induction. Such generators may be, inter alia, AC or DC generators. Generators may, inter alia, be asynchronous generators. Thermoelectric generators may also be used to convert thermal energy into electrical energy.

[0012] As may be used herein, the terms "comprises," "contains," "includes," "has," "having," "with," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method or device comprising or having a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such method or device.

[0013] Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, condition A or B is satisfied by one of the following conditions: A is true (or exists) and B is false (or does not exist), A is false (does not exist) and B is true (or exists), and both A and B are true (or exist).

[0014] The terms "a" or "an," as used herein, are defined as meaning "one or more." The terms "another" and "further," and any other variations thereof, are to be understood as meaning "at least one other."

[0015] The term "plurality" as may be used herein should be understood to mean "two or more."

[0016] The terms "configured" or "setup" to perform a particular function (and respective modifications thereof), as may be used herein, should be understood to mean that the corresponding device or component thereof is already provided with a design or configuration capable of performing the function, or that it is at least configurable, i.e., configurable, so that it can perform the function after corresponding configuration. Configuration can be performed, for example, through corresponding setting of parameters of a process sequence for activating or deactivating the function or setting, or corresponding setting of a switch, etc. Specifically, a device can have multiple predefined configurations or operating modes, whereby configuration can be performed by selecting one of these configurations or operating modes.

[0017] In the energy supply system according to the first aspect, in addition to the fuel cell system, at least one generator is also available to generate electrical energy that can be supplied by the energy supply system. Since the energy supply by the fuel cell system can fluctuate for various reasons, the energy supply system therefore has the possibility to effectively and quickly compensate for such fluctuations with the electrical energy variably supplied by the at least one generator, thus achieving stabilization, in particular stabilization of the supply voltage supplied by the energy supply system. In this way, for a given target output energy of the energy supply system, the electrical energy directly supplied by the fuel cell can also be reduced, since an additional electrical energy contribution can be supplied by the generator(s) to achieve the target output energy overall.

[0018] Fuel cell systems with multiple fuel cell stacks (stacks), each designed as an assembly and at least two of which are connected in series to provide an electrical output voltage present across this series circuit to provide electrical energy that can be generated by the energy supply system, are particularly advantageous in combination with a parallel circuit with a battery. In particular, in energy supply systems for supplying power to vehicle drives, the batteries are often so-called high-voltage batteries, i.e., batteries with an output voltage exceeding 60 V (typically several hundred volts, for example 400 V, 800 V or 900 V) and therefore also exceeding the nominal voltage of common low-voltage automotive batteries, which are typically 12 V or 24 V. By connecting several stacks in series, a sufficiently high supply voltage can be (jointly) generated by the fuel cell system.

[0019] Various exemplary embodiments of the energy supply system according to the first aspect are described below, which can be combined as required with each other and with the second aspect of the solution, unless in each case expressly excluded or technically impossible, as described below.

[0020] In some embodiments, the energy supply system further includes (i.e., at least one) electrochemical battery, in particular an accumulator, and the third voltage output is for providing a third output voltage that can be supplied by the battery. The energy supply system has a parallel circuit with two poles that provides a supply voltage that can be taken between the poles. In a first branch of the parallel circuit, the first voltage output and at least one second voltage output are connected to each other in series or in parallel. The third voltage output is instead located in a second branch of the parallel circuit, connected in parallel with the first branch. In this way, the advantages of both a fuel cell system and a battery can be used to provide the supply voltage. On the one hand, the battery is immediately ready for use, in particular during cold starts of an electric vehicle drive operated by the energy supply system, and on the other hand, it also supports regeneration (whereby the battery is at least partially recharged). The advantage of a fuel cell system lies in the area of ​​stable energy supply, particularly over long periods of time (e.g., over longer journeys). This stability, as well as the energy efficiency or effectiveness of the energy supply system, can be further enhanced by at least one generator, as already explained above. In particular, in energy supply systems for powering vehicle drives, the batteries are often so-called high-voltage batteries, i.e. batteries with an output voltage above 60 V (typically several hundred volts, e.g. 400 V, 800 V or 900 V) and therefore also above the nominal voltage of common low-voltage automotive batteries, which are typically 12 V or 24 V. By connecting several stacks in series, a sufficiently high supply voltage can be generated by the fuel cell system also (jointly) in the first branch of the parallel circuit.

[0021] In some embodiments, depending on its currently employed configuration, the energy supply system may adjust the supply voltage to: (a) Both the fuel cell system and the battery (b) a fuel cell system rather than a battery; or (c) Battery, not fuel cell system , which can be configured to be variable in time depending on the control.

[0022] In addition, the energy supply system is configurable in time, depending on the control, such that in one of the configurations adjustable by the control, no supply voltage is provided that can be drawn between the poles using either the fuel cell system or the battery.

[0023] Overall, a three- or four-quadrant control system can be established, in which the use of the fuel cell system and the battery can be individually activated or deactivated to provide the supply voltage. Depending on the current requirements of the energy supply system, the appropriate configuration of the energy supply system can be variably set (even, especially during operation). For example, in the case of the above-mentioned cold start, the battery can be used while the fuel cell system is simultaneously started. Thus, if available, the first branch can be used alone or in combination with the second branch to provide the supply voltage, ensuring an optimal, especially long-term, stable voltage supply (e.g., during long road trips). The supply voltage can also be switched off by disconnecting both the fuel cell system and the battery from at least one of the poles (e.g., via an appropriate switch). In the case of a fuel cell system, shutting down can also include stopping the fuel supply.

[0024] In some embodiments, the second voltage output of at least one of the generators is electrically coupled to the first voltage output, particularly by a respective first rectifier device, such that the current path from the at least one fuel cell to the at least one generator in the first branch of the parallel circuit runs in the forward direction of the first rectifier device, while the current path from the at least one generator to the at least one fuel cell in the first branch runs in the reverse direction of the first rectifier device. This prevents unwanted or harmful current flow from the generator to the fuel cell system, and more precisely, to one or more fuel cells. This also ensures that the predetermined polarity of the supply voltage is maintained.

[0025] In some embodiments, the first and second branches of the parallel circuit are electrically coupled through a second rectifier device such that current flow from the first branch to the second branch of the parallel circuit is in the forward direction of the second rectifier device, but conversely, current flow from the second branch to the first branch of the parallel circuit is in the reverse direction of the second rectifier device. Thus, the second rectifier device, which may be a single diode in particular, disconnects the battery from the series circuit of the fuel cell system with at least one generator in the first branch, so that the left branch can source, but not receive, electrical energy (or current) through the path of the second rectifier device. Therefore, to source energy from the first branch, the voltage across the first branch must exceed at least the rectification threshold voltage of the second rectifier device (in the case of a single diode, its threshold voltage in the forward direction) to provide such energy transfer (via current flow) from the first branch.

[0026] In some embodiments ("efficiency variants"), the energy supply system is designed in such a way that during its operation at least one of the generators is driven at least in part by energy provided by the fuel cell system in the form of non-electrical energy, which allows for a particularly energy-efficient implementation and an overall (further) improvement in the efficiency of the energy supply system.

[0027] There are various options available here.

[0028] Specifically, in some embodiments ("thermal power variant"), the energy supply system further includes a heat engine for implementing a thermodynamic cycle to supply at least one of the generators with kinetic energy, which is converted into electrical energy by the respective generator. The heat engine may in particular be a Stirling engine or may be operable at least approximately according to the Stirling cycle known from thermodynamics. Alternatively, other types of heat engines or thermodynamic cycles are also conceivable, in particular depending on the application. What is important here is that the thermal energy available to the energy supply system, in particular its fuel cell system, can be proportionally converted into kinetic energy for driving the generator driven by the heat engine.

[0029] These heat output variants can also represent efficiency variants (as defined above), especially if the heat engine is configured to use waste heat from a cooling circuit for cooling at least one fuel cell as a heat source for the thermodynamic cycle. Thus, the "warm side" or "warm heat reservoir" of the heat engine is at least partially provided by the cooling circuit, for example, via a heat exchanger. This means that otherwise unused waste heat, generated "almost as a side effect" during the operation of the fuel cell system, can be used to drive the generator and thus generate part of the supply voltage. In addition to the voltage stabilization mentioned above, the efficiency of the energy supply system can also be improved. This is because the electrical energy obtained from the waste heat by the generator does not need to be electrochemically generated as electrical energy by the fuel cell system (or battery, if present). This concept of combined heat and power can also be used in electrolysis systems (which can be considered the "reverse" of a fuel cell system). Thus, the waste heat generated during electrolysis can be partially recovered and used as electrical energy.

[0030] In some embodiments, the heat engine is configured to use cooled, particularly cryogenic, fuel for the fuel cell system or a cooling fluid as a heat sink for the thermodynamic cycle, which is supplied to the energy supply system at a temperature below the operating temperature of at least one fuel cell. The fuel for the fuel cell system is supplied at a low (particularly cryogenic) temperature, for example, in a cooled and / or well-insulated fuel tank (e.g., a hydrogen tank). The fuel or a body cooled thereby, e.g., the fuel tank wall, can thus function as a heat sink ("cold side" or "cold reservoir") for the heat engine, for example, via a heat exchanger. It makes sense to do this in such a way or at such a location that the fuel is heated to the desired operating temperature for use in the fuel cell(s). These embodiments also result in efficiency advantages, since a "dual-use" cold reservoir already available for the fuel cell system can be used without the need to create one for the operation of the heat engine.

[0031] In some heat output variants, in which the energy supply system also has a first rectifier device and / or a second rectifier device (as already mentioned above), the first rectifier device and / or the second rectifier device are each thermally coupled to the heat engine so that they can act as a heat source for supplying the heat generated during rectification to the thermodynamic cycle. Thus, waste heat generated in the respective rectifier device during rectification can be used proportionately to (further) supply heat to the thermodynamic cycle of the heat engine. This also helps to improve the efficiency, especially in terms of the achievable efficiency of the energy supply system.

[0032] In some embodiments ("decompression variant"), an additional drive concept is used for at least one of the generators instead of or in addition to the above-mentioned thermal power variant. In particular, at least one of the generators is configured to be at least partially driven by a fluid movement, in particular a mass flow, that occurs when a compressed (in particular cryogenic) fluid used as fuel for the fuel cell system expands. In particular, an expansion device, such as a turbine, can be provided, which is driven by a fluid movement that occurs during the expansion (decompression) of the fuel during operation of the energy supply system, and consequently drives at least one of the generators.

[0033] In fuel cell systems, expansion is typically provided to bring a fuel (e.g., hydrogen) that is normally stored under pressure (e.g., in a pressure tank) into a pressure state compatible with the fuel cell(s), which is typically at or near ambient pressure (i.e., normal pressure) or slightly higher. In a decompression variant, the energy reservoir already provided for normal operation of the fuel cell system can also be used to at least partially drive at least one of the generators. This also helps to improve efficiency, particularly with regard to the achievable efficiency of the energy supply system. An example of an expansion device that can be used for this purpose is described in DE 10 2011 115 160 A1.

[0034] The thermal power variant can also be combined with a pressure reduction variant. This can be done in such a way that the first of the generators (according to the thermal power variant) is driven by a heat engine, and the second of the generators (according to the pressure reduction variant) is driven by the movement of an expanding compressed fluid used as fuel in the fuel cell system. In the case of a series circuit, the first voltage output is connected in series with the second voltage output of the first generator, which is connected in series with the second voltage output of the second generator. In this way, particularly high energy efficiency can be achieved, since both the thermal power and the pressure reduction are used to provide additional energy to the energy supply system in the sense of energy recovery. This therefore also helps to increase efficiency, especially with regard to the achievable efficiency of the energy supply system.

[0035] A second aspect of the solution relates to an electric drivetrain of a vehicle, in particular a motor vehicle, comprising a vehicle drive with at least one electric drive motor and an energy supply system according to the first aspect, in particular according to one or more of the embodiments described herein, for supplying the vehicle drive with electric energy. In this way, the advantages of the energy supply system, as already mentioned in relation to the first aspect of the solution and explained in detail above, can be particularly utilized for the vehicle drive.

[0036] Further advantages, features and possible applications of the invention emerge from the following description in more detail in conjunction with the figures. [Brief explanation of the drawings]

[0037] [Figure 1] 1 shows a schematic representation of a first exemplary embodiment of an energy supply system; [Figure 2] In particular, according to FIG. 1, the current-voltage characteristics (polar curves) of a fuel cell system and a lithium-ion battery, respectively, as components of an energy supply system are shown diagrammatically. [Figure 3]FIG. 1 is a block diagram of an exemplary embodiment of a drivetrain including an energy supply system. [Figure 4] 2 shows a schematic representation of a second exemplary embodiment of an energy supply system. DETAILED DESCRIPTION OF THE INVENTION

[0038] In the drawings, the same reference numbers indicate identical, similar, or corresponding elements. The elements shown in the drawings are not necessarily drawn to scale. Rather, the various elements shown in the drawings are presented so that their function and general purpose can be understood by those skilled in the art. The connections and couplings shown in the drawings between functional units and elements can also be implemented as indirect connections or couplings, unless otherwise specified.

[0039] FIG. 1 illustrates a first exemplary embodiment 100 of an energy supply system, with many functions or components of the energy supply system 100 grouped into blocks for simplified representation.

[0040] The headings introduced in the following description of Figure 1 are merely for the purpose of improving readability and clarity and are not to be understood as any kind of limitation of the content. In particular, various features or advantages of the described solutions that may be assigned to one of the headings may additionally be listed, or may instead be listed under one or more other headings.

[0041] The energy supply system 100 comprises an electrical parallel circuit in which a first branch 105 and a second branch 110 are connected in parallel. During operation of the energy supply system 100, the supply voltage U V can be extracted via a pair of electrodes having a positive electrode 155a and a negative electrode 155b and can be used, in particular, to supply an electric drive unit of an electric vehicle, for example.

[0042] A) First branch The first branch 105 of the parallel circuit comprises a series circuit of several components.

[0043] 1. Fuel cell system One of these components is fuel cell system 115. In this embodiment, the fuel cell system includes four series-connected fuel cell stacks (stacks) 115a-115d, each stack having a series circuit of multiple fuel cells. For example, each of stacks 115a-115d may include 245 individual fuel cells connected in series, resulting in fuel cell system 115 having a total of 980 fuel cells. This allows, for example, for the output voltage U of fuel cell system 115 to be varied depending on the stack configuration and operating mode. FCS ("first" voltage), especially U FCS With a voltage output ("first" voltage output) defined by the opposite poles of the series circuit of stacks in the range of values ​​= 500 V to 1000 V, it is possible to generate a current I of 600 A. However, other circuits are also conceivable, in particular with configurations in which two stacks are connected in series and these two series circuits are connected in parallel with each other. Other configurations are also conceivable, in particular with configurations having a different number of stacks.

[0044] The fuel cell system 115 also includes a cooling circuit 115e configured to circulate a cooling fluid having a temperature below the operating temperature of at least one fuel cell through cooling channels in the stacks 115a-115d to at least partially absorb and dissipate waste heat generated during operation of the fuel cells to prevent overheating of the fuel cell system 115. Thus, the cooling circuit 115e typically also includes a cooler so that the dissipated waste heat can be extracted from the cooling circuit 115e before the coolant is returned to the cooling channels to flow again.

[0045] Additionally, the fuel cell system 115 includes a pressure tank 115f for storing fuel for the fuel cell under pressure, which may be, among other things, hydrogen or methanol in a gaseous or liquid state that is present in the pressure tank at an extremely low temperature (cryogenic).

[0046] 2. Heat engine with first generator As a further component, the first branch 105 of the parallel circuit includes a first electrical generator 125 connected in series with the (first) voltage output of the fuel cell system 115 driven by the heat engine 120. The heat engine 120 is configured to perform a (clockwise) thermodynamic cycle on a working medium to obtain kinetic energy from thermal energy. It at least partially uses the cooling circuit 115e as a heat source for its "warm side," i.e., its "warm" temperature reservoir. In this way, waste heat, or more precisely, its coolant, dissipated from the fuel cell system 115 as a heat flow 120a by the cooling circuit 115e can be partially converted into kinetic energy and used to drive the generator 125.

[0047] In particular, the cooled fuel in pressure tank 115f can function as a heat sink for the "cold side" or "low" temperature reservoir of heat engine 120, thereby extracting heat from the cold side of the heat engine via heat (exhaust) flow 120b. Additionally or alternatively, coolant in another cooling circuit, for example, a cooling circuit with a vehicle radiator in a vehicle supplied with electrical energy by energy supply system 100, can be used as another heat sink for the low temperature reservoir. For simplicity of illustration, this other (optional) heat sink is not shown in FIG. 1.

[0048] During operation, the first generator 125 generates an induced voltage in a known manner via electromagnetic induction across inductances L1-L3, resulting in a three-phase AC output voltage ("second" output voltage) present at multiple phases of the generator 125, specifically at voltage output 125a. The "first" voltage output of the fuel cell system 115 and voltage output 125a of the generator 125 are thus connected in series via a rectifier (specifically a diode) D4. The rectifier D4 is positioned such that current flow from the fuel cell system 115 to the generator 125 is in the forward direction of the rectifier D4, while current flow in the opposite direction is prevented. This prevents current from flowing back into the fuel cell system, which could damage the fuel cell system.

[0049] The rectifier D4 may be conveniently combined with other rectifiers D1-D3 provided for rectifying the multi-phase second output voltage of the generator 125 as a rectifier device 130, for example on a common printed circuit board (PCB) and / or a common heat sink. Thus, across the first rectifier device, the first generator voltage U G1 occurs during operation of the generator 125 and is given by the voltage produced by the generator 125 after its rectification by the rectifiers D1 to D3 (one per phase).

[0050] During operation, the rectifiers D1-D4 generate a heat output which may be in the range of several hundred watts or more in the case of, for example, the energy supply system 115 of a vehicle such as a truck. This heat output may also contribute to the heat flow 120a for supplying heat to the heat engine 120, for example indirectly via a heat exchanger or directly by thermal contact with the coolant of the cooling circuit 115e of the rectifier device 130.

[0051] 3. Inflating device with a second generator As yet another component, the first branch 105 of the parallel circuit includes a second electric generator 140 connected in series with the (second) voltage output 125a of the first electric generator 125 (and indirectly with the voltage output of the fuel cell system 115), which is driven by an expansion device 135 and may, in particular, be structurally identical to the first electric generator 125. The expansion device 135 is configured to obtain kinetic energy for driving the electric generator 140 from the expansion (i.e., decompression) of a compressed fluid, in particular, a pressurized fuel for the fuel cell system 155. Specifically, the expansion device 135 may include one or more turbines for converting the mass flow of fuel generated during the expansion of the fuel into directed kinetic energy for driving the second electric generator 140. Other energy converters for this purpose are also contemplated.

[0052] Similar to the generator 125, the generator 140 converts the kinetic energy that drives it into electrical energy according to its respective efficiency and can provide a resulting multi-phase, here particularly three-phase, AC output voltage (the "second" output voltage of the generator 140) at the voltage output 140a, which is rectified by the rectifier device 145. The rectifiers D1-D3 of the rectifier device 130 already perform the task of a "check valve," and in the case of the first generator 125, the rectifier D4 also performs this task. Therefore, the rectifier D4 can optionally be omitted in the rectifier device 145 (as shown in FIG. 1 ) to avoid an unnecessary further voltage drop across the first branch 105. As in the case of the rectifier device 130, the waste heat generated in the rectifier device 145 can also be at least partially coupled to the heat flow 120a directed to the heat engine 120.

[0053] The positive pole 105a of the first branch 105, located after the rectifier device 145, is electrically coupled to the second branch 110 of the parallel circuit via a further ("second") rectifier device 150, which may optionally include only a single diode (in particular, a power diode) as a rectifier. Thus, when the electrical voltage across the first branch 105 is higher than the voltage across the second branch 110 by at least the threshold voltage of the rectifier device 150, the flow of current and thus the transfer of electrical energy from the first branch to the second branch is allowed. However, in the opposite direction, such current or energy flow is at least substantially blocked (i.e., within the blocking capability of the rectifier device 150) by the rectifier device 150.

[0054] B) Second branch The second branch 110 of the parallel circuit comprises at least one electric battery 160, in particular a high-voltage battery (and optionally further components such as a cooling system, power electronics, etc.), for example a lithium-ion battery (suitably designed as an accumulator and therefore rechargeable, which, when charged, generates a battery (DC) voltage U BAT Optionally, depending in particular on the application, further electrical components may be present in the second branch 110 (although this is not the case in the present exemplary embodiment).

[0055] C) 4 quadrant operation a supply (DC) voltage U that can be taken off via a parallel circuit and supplied by the energy supply system 115 during its operation; V can therefore be supplied both from the first branch 105, in particular from the fuel cell system 115, and from the second branch 110, and therefore from the battery 160. This is because the two branches can each be selectively used to provide a supply voltage U Vcan be supplied in a controlled manner according to four-quadrant operation, in particular. For this purpose, corresponding switches 165a and 165b can be provided in particular, which can be controlled via associated control signals to switch them on and off.

[0056] 1, switch 165a can be used to selectively connect (or disconnect) the positive terminal of the first branch 105 to (or from) the positive terminal 155a of the overall energy supply system. Correspondingly, switch 165b can be used to selectively connect (or disconnect) the positive terminal of the second branch 110 to (or from) the positive terminal 155a of the overall energy supply system. This results in four circuit options (quadrants):

[0057] (a) Both switches 165a and 165b are closed: supply voltage U V can in particular be provided mainly by the fuel cell system, while the generator serves to increase the efficiency and / or stabilize the output voltages of the first and second branches, and the second branch 110 (specifically the battery 160) can be used mainly for very short-term power increase requests and for regeneration in cases such as vehicle driving. In addition, in this quadrant, charging of the battery 160 is possible with the electrical energy available from the first branch 105.

[0058] (b) Switch 165a open, switch 165b closed: This quadrant is particularly suitable for the start-up process of the energy supply system when the fuel cell system has not yet ramped up. Until it is available, the necessary energy demands can be covered (within the performance and capacity of the battery 160) by the second branch 110 alone.

[0059] (c) Switch 165a closed, switch 165b open: This quadrant is particularly suited for the operating case where the fuel cell system is already available for power output and the battery is either fully charged or defective. Then, the supply voltage U Vcan be supplied solely from the first branch.

[0060] (d) Both switches 165a and 165b are open: This quadrant is active when at least the energy supply system is operating at a supply voltage U V This results in a shutdown of the energy supply system, in the sense that it can no longer provide the required power. In particular, this switch position can also be used for short-term, temporary shutdowns, such as when an error is detected. By using switches 165a and 165b here, the shutdown generally occurs more quickly than would be possible by shutting down the entire fuel cell system 115 or first branch 105.

[0061] For further explanation of the energy supply system 100 and its operation, a current-voltage characteristic curve 200 (so-called polar curve U(I)) is shown schematically in FIG. 2 for the fuel cell system 115 and the battery 160 (here specifically a lithium-ion battery) as components of the energy supply system 100 of FIG. 1.

[0062] Characteristic curve U FCS (I) and U BAT Both (I) and (I) have essentially linear courses at medium currents, but they rapidly increase in slope towards small currents I and large currents I. On the other hand, the characteristic curve U of the battery 160 BAT (I) The characteristic curve of a fuel cell system is essentially fixed (except for the effects of aging, damage, etc.) due to its electrochemical properties, and the characteristic curve of a fuel cell system can be specifically adjusted to vary within a certain variation range 205 during its operation, since the output voltage delivered by a fuel cell (particularly of the PEM type) is variable by changing the media supply (fuel and oxidant) with their respective pressures.

[0063] In addition, the characteristic curve of the entire first branch 105 is G1 and U G2To this end, in particular with respect to the first generator 125, the heat supply to the heat engine 120 can be changed accordingly, and / or with respect to the second generator 140, the coupling of the expansion device to the expansion movement of the fuel can be changed (e.g., in the case of a turbine, by adjusting the turbine blades).

[0064] In general, the characteristic curve of the entire energy supply system 100 shows that during load operation with increasing current, the output power P increases, but the efficiency η and the expected service life L of the energy supply system 100 decrease. Against this background, a particularly suitable operating point 210 is located at or near the intersection of the characteristic curves of both branches 105 and 110. In addition to the characteristic curve of the fuel cell system 115 itself, to determine the characteristic curve of the first branch 105, it is also preferable to take into account the voltage drops occurring between the fuel cell system 115 and the poles 155a (in particular the voltage drops at the rectifier devices 130, 145 and 150 and / or the generators 125 and 140, respectively) in order to achieve greater accuracy. The achievement and maintenance of this operating point (and any other operating point) can be controlled by the aforementioned variations of the characteristic curve of the first branch 105.

[0065] FIG. 3 is a block diagram of an exemplary embodiment of a drivetrain 300 including the energy supply system 100 .

[0066] First, the parallel circuit of the first branch 105 and the second branch 110 can be seen again in Figure 3. The details of the two branches 105 and 110 are not shown again here for clarity. The two branches 105 and 110 are electrically coupled in parallel to each other via a power interface 305.

[0067] The power interface 305 has a pyrotechnic closure device 310 on the input side from the first branch 105, by means of which the connection between the two branches can be pyrotechnically separated in an emergency situation. In the case of a vehicle, the pyrotechnic closure device 310 can be triggered as a function of sensor signals from one or more crash sensors, in particular those that can also be used to control airbags.

[0068] Furthermore, the power interface 305 comprises a safety switch device that can also interrupt the electrical coupling between the two branches 105 and 110 in a reversible and targeted manner, in particular depending on a corresponding control signal. Thus, control of the pyrotechnic closure device 310 and / or the safety switch device 315 via respective associated sensors or control signals can be performed via an electrical signal input 320 of the power interface 305. Additional signal inputs (not shown) can be configured to control the switches 165a,b of Figure 1 .

[0069] Additionally, the aforementioned (second) rectifier device 150 is again provided on the positive side between the two branches 105 and 110 .

[0070] The power interface 305 further comprises an external electrical connection 325 followed by a fuse 330 which protects the electrical connection to the two poles 155a and 155b and thus to the pole of the second branch 110 which carries the battery 160. The battery 160 can therefore be electrically accessed from the outside via the connection 325 in order to charge it or for measurements.

[0071] An electric drive 335, for example an electric drive motor for an electric vehicle, is driven by a supply voltage U supplied by the energy supply system 100. V 155a and 155b of the energy supply system 100 so that the power supply is supplied using the

[0072] FIG. 4 illustrates a second exemplary embodiment 400 of an energy supply system, with many functions or components of the energy supply system 400 grouped into blocks for simplified representation.

[0073] While the first embodiment according to Fig. 1 has a series circuit of the fuel cell system with the generators 125 and 140 in its first branch 105, the second embodiment 400 according to Fig. 4 has a parallel circuit in which the fuel cell system 115 is located in a first branch of the parallel circuit, the battery 160 is located in a second branch of the parallel circuit, and the series circuit of the two generators 125 and 140 is located in a third branch of the parallel circuit. The battery 160 and the fuel cell system 115 are protected by respective blocking diodes 150 and 170, although at least the blocking diode 150 is optional. The first and third branches can also be considered collectively as a "first" branch, so that the series circuit of the generators 125 and 140 and the fuel cell system 115 connected in parallel thereto define the first branch, and the battery 160 defines the second branch. Line 175 shows an alternative connection of the fuel cell system 115, where the combination of a generator connected in series with a fuel cell system 115 connected in parallel to it becomes more clearly visible as the "first" branch. [Explanation of symbols]

[0074] 100 Energy supply system, first embodiment 105 First branch of parallel circuit 105a Positive pole of the first branch 105 110 Second branch of parallel circuit 115 Fuel Cell System 115a-d fuel cell stack (stack) 115e a cooling circuit for cooling the fuel cell of the fuel cell system 115 115f Pressure tank for cooling fuel for fuel cell system 120 Heat Engine 120a Heat flow from heat source(s) to heat engine 120b Heat flow from the heat engine to the heat sink(s) 125 First Electric Generator 125a Generator 125 voltage output 130 first rectifier device 135 Expansion devices, e.g. turbines 135a Expanding fuel mass flow 140 Second Electric Generator 140a Voltage output of generator 140 145 Further, in particular the first, rectifier device 150 second rectifier device, in particular (power) diode(s) 155a, b Supply voltage U V poles for outputting 160 battery(ies) 165a, b switch 170 Blocking Diode 175 Alternative connections for fuel cell system 115 200 characteristic curve 205 Fuel cell characteristic curve UFCS (I) Operation-dependent variation range 210 Preferred Operating Point 300 Drivetrain 305 Power Interface 310 Pyrotechnic Closing Device 315 Safety switches (especially contactors) 320 signal input 325 Connection for external power supply (e.g. for battery charging) 330 Fuse 335 Electric drives, in particular electric drive motors for electric vehicles 400 Energy supply system, second embodiment D1~D4 Rectifiers, especially diodes L1~L3 Inductance (coil) of generator 125 or 140 L Service life η efficiency P power U BAT Battery output voltage U FCS Fuel cell system output voltage ("first" voltage) U G1 Generator voltage of the first generator (after rectification) U G2 Generator voltage of the second generator (after rectification) U V The supply voltage provided by the energy supply system U Voltage I current

Claims

1. An electric energy supply system (100) for the autonomous energy supply of an electric vehicle drive (335), in particular, said energy supply system (100) comprising: A fuel cell system (115) comprising at least one fuel cell and a first voltage (U) deliverable by said fuel cell system (115). ＦＣＳ the fuel cell system (115) having a first voltage output for providing a at least one electrical generator (125, 140), each having a second voltage output (125a, 140a) for providing a respective second voltage generated by said respective generator (125, 140); Including, In the context of an electrical interconnection, the first voltage output is a supply voltage (U) present across a series or parallel circuit for providing electrical energy that can be produced by the energy supply system (100). Ｖ ) connected in series or parallel to at least one of the second voltage outputs to provide a the fuel cell system (115) includes a plurality of fuel cell stacks (115a-d), each designed as an assembly, at least two of which are connected in series and provide an electrical output voltage present across the series connection to provide electrical energy that can be produced by the energy supply system (100); The electrical energy supply system (100).

2. The method further includes an electrochemical battery (160), the battery (160) having a third output voltage (U ＢＡＴ a third voltage output for providing a The energy supply system (100) comprises a parallel circuit with two poles (155a, b) and a supply voltage (U Ｖ ) and In a first branch (105) of the parallel circuit, the first voltage output and at least one second voltage output are connected in series or in parallel with each other, the third voltage output is located in a second branch (110) of the parallel circuit, connected in parallel with the first branch (105); The electrical energy supply system (100) of claim 1.

3. The energy supply system (100) is time-variably configurable depending on the control, and depending on the currently adopted configuration, the energy supply system (100) controls the supply voltage (U Ｖ )of, (a) both the fuel cell system (115) and the battery (160); (b) the fuel cell system (115) rather than the battery (160); or (c) the battery (160) rather than the fuel cell system (115) The energy supply system (100) of claim 2, wherein the energy supply system (100) can be supplied using

4. The energy supply system (100) is also configurable in time variably according to the control, and in one of the configurations adjustable by the control, a supply voltage (U) that can be drawn between the poles (155a, b) using either the fuel cell system (115) or the battery (160) is Ｖ 4. The energy supply system (100) of claim 3, wherein the energy supply system (100) does not supply a

5. 5. The energy supply system of claim 2, wherein the second voltage output of each of the at least one generator is electrically coupled to the first voltage output by a first rectifier device, and wherein in the first branch of the parallel circuit, a current path leading from the at least one fuel cell to the at least one generator extends in a forward direction of the first rectifier device, and conversely, in the first branch, a current path leading from the at least one generator to the at least one fuel cell is in a reverse direction of the first rectifier device.

6. 6. The energy supply system (100) of claim 2, wherein the first branch (105) and the second branch (110) of the parallel circuit are electrically coupled via a second rectifier device (150), and current flow from the first branch (105) to the second branch (110) of the parallel circuit is in a forward direction of the second rectifier device (150), and conversely, current flow from the second branch (110) to the first branch (105) of the parallel circuit is in a reverse direction of the second rectifier device (150).

7. 10. The energy supply system (100) according to any one of the preceding claims, wherein during its operation, at least one of the generators (125, 140) is designed to be driven, at least in part, using energy provided by the fuel cell system (115) in the form of non-electrical energy.

8. 10. The energy supply system (100) according to any one of the preceding claims, further comprising a heat engine (120) for performing a thermodynamic cycle for supplying at least one said generator (125) with kinetic energy which is converted by said generator (125) into electrical energy.

9. 9. The energy supply system (100) of claim 8, wherein the heat engine (120) is configured to use waste heat from a cooling circuit (115e) for cooling at least one of the fuel cells as a heat source for the thermodynamic cycle.

10. 10. The energy supply system (100) of claim 8 or 9, wherein the heat engine (120) is configured to use cooled fuel for the fuel cell system (115) or a fluid coolant supplied to the energy supply system (100) as a heat sink for the thermodynamic cycle.

11. The energy supply system (100) according to any one of claims 8 to 10, in combination with claim 5 or 6, respectively, wherein the first rectifier device (130) and / or the second rectifier device (150) are thermally coupled to the heat engine (120) and each function as a heat source and can supply heat generated during rectification to the thermodynamic cycle.

12. 10. The energy supply system (100) of claim 1, wherein the at least one generator (140) is configured to be at least partially powered by a displacement of a compressed fluid due to expansion of the fluid used as fuel for the fuel cell system (115).

13. A first generator of the generators (125, 140) according to any one of claims 8 to 11 is driven by a heat engine (120), A second generator of the generators (125, 140) of claim 12 is driven by the movement of an expanding compressed fluid used as fuel for the fuel cell system (115); In the series circuit situation, the first voltage output is connected in series with the second voltage output (125a) of the first generator and the second voltage output (140a) of the second generator. An energy supply system (100) according to any one of the preceding claims.

14. An electric drivetrain (300) for a vehicle, in particular for an automobile, comprising: a vehicle drive unit (335) comprising at least one electric drive motor and an energy supply system (100) according to any one of the preceding claims for supplying the vehicle drive unit (335) with electric energy, The electric drivetrain (300).

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