METHOD FOR OPERATING A COMMERCIAL VEHICLE TRAIN AND COMMERCIAL VEHICLE TRAIN

Description

[0001] The invention relates to a method for operating a commercial vehicle combination with a tractor unit comprising a first electric machine, a first electrical storage device connected thereto, and a fuel cell system connected to the first electrical storage device and configured to provide electrical energy at a generation power, and with a trailer comprising a second electric machine and a second electrical storage device connected thereto.

[0002] In the operation of commercial vehicle combinations of the aforementioned type, the fuel cell systems used in the tractor units are regularly subjected to changes in load requirements. These changes in load requirements are also summarized under the general term "dynamic load." The more dynamic the load on the fuel cell system during operation, for example, due to the topography of the route taken by the commercial vehicle combination, the higher the dynamic demands on the reactant supply of the fuel cell system, such as the air supply. The usable size of compressors and compressor assemblies in commercial vehicles is limited by space constraints, and larger compressor assemblies are less dynamic than smaller ones. However, fuel cell systems in commercial vehicle combinations require comparatively large compressor systems, resulting in an increased air demand.

[0003] Due to the resulting limitations in dynamics, fuel cell systems in commercial vehicle combinations cannot react particularly quickly, i.e., dynamically, to changing load requirements. Furthermore, dynamic stress on the fuel cell systems reduces their service life.

[0004] Despite the ever-increasing functionality of fuel cell systems in commercial vehicles, a need for improvements is seen.

[0005] From DE 10 2014 224 380 A1 a cooling system for a fuel cell system is known in which navigation information is used to determine the driving cycle and subsequently to determine the coolant requirement.

[0006] The fundamental problem of the limited dynamic load capacity of fuel cell systems is also known from DE 10 2014 217 780 A1. This document proposes that, in the future, operating parameters necessary for operation should be predicted in advance to better assess upcoming load demands. Load change assessments are carried out by drivers, and according to the proposal in DE 10 2014 217 780 A1, detour information, uphill driving, and traffic jams can be predicted via navigation systems.

[0007] From DE 10 2017 109 410 A1 a proposal is known according to which charging and discharging profiles of electrical energy storage devices are recorded and the future demand is to be determined from this by means of a forecasting unit.

[0008] DE 10 2013 014305 A1 discloses a vehicle trailer for a towing vehicle, wherein the vehicle trailer has electrical drive components that can be coupled to the drive components of the towing vehicle.

[0009] US 2021 / 188279 A1 discloses a method for operating a commercial vehicle combination with electric drive components in the tractor unit and trailer. The method describes the interaction of the electric motors and energy storage devices of both vehicles. It includes control measures for coordinating the drive systems.

[0010] Several approaches are known from the state of the art that relate to the improved operation of a tractor unit with fuel cell systems in general. However, none of them propose a concrete solution and are therefore not optimal for the actual operation of commercial vehicle combinations consisting of a tractor unit and trailer with a separate electric drive.

[0011] Accordingly, the present invention was based on the objective of providing a method of the type described above which largely overcomes the disadvantages described above. In particular, the invention was based on the objective of providing a method for operating a commercial vehicle combination of the type described above which enables more efficient operation of the commercial vehicle combination without impairing the service life of the fuel cell system of the tractor unit.

[0012] The invention solves the underlying problem by providing the method with the steps according to claim 1.

[0013] The invention is based on the idea that, to adjust the power output to be provided by the fuel cell, the electrical operating parameters of the entire system, consisting of the tractor unit and trailer, are determined. This allows the trailer, as part of the commercial vehicle combination with its dedicated electric motor and energy storage system, to be integrated into the control of the fuel cell's power output. The trailer and its electrical power components are thus made visible for the control of the tractor unit's fuel cell system. In normal operating mode, the trailer's electric motor can provide additional drive power, and in recuperation mode, it can provide additional recuperation power.To fully utilize the potential of the tractor-trailer combination, the invention follows the approach of jointly considering the storage capacities and performance of both electric machines in order to adjust the generation power to be provided by the fuel cell accordingly. Over the lifetime of the fuel cell system, this control system allows for a lower average load on the fuel cell and, due to the higher amount of storable electrical energy, better energy buffering because recuperation is improved and the adjustment of the generation power enables a less dynamic load on the fuel cell system.

[0014] The tractor and the trailer can each have one or more electric machines, just as they can each have one or more electrical storage devices. It goes without saying that the procedure allows the determination of operating parameters for one, several, or all of the electric machines and / or electrical storage devices when using multiple electric machines and / or electrical storage devices.

[0015] In preferred embodiments, the determination may include reading out permanently stored information or data, and / or capturing state variables from the ongoing operation of the electrical machine(s) or storage device.

[0016] When a fuel cell system is mentioned in connection with the invention, it is understood that the fuel cell system comprises a fuel cell which is configured to be operated at a variable operating point, wherein the operating point is set as a function of one or more of the operating parameters described above, preferably by a fuel cell controller.

[0017] The fuel cell control unit is part of a higher-level vehicle control system, which may include one or more additional control units besides the fuel cell control unit, in preferred embodiments such as one, several or all of the following: battery management system, tractor brake control unit, and / or trailer brake control unit.

[0018] The vehicle control system can be designed as a central computer-aided fuel cell control system and may include the aforementioned devices as hardware- or software-integrated components or be designed in the form of several dedicated control units, which together perform the method according to the invention and are provided with the corresponding processors, data storage devices and programmed control commands for this purpose.

[0019] The process has two characteristic operating phases: a normal operating mode in which the electric machines are controlled as electric motors to drive the commercial vehicle combination, and a recuperation mode in which the electric machines are controlled as generators for regenerative braking. In other words, the process also includes the following steps at certain times: Providing electrical energy at a generation output using the fuel cell system, and optionally a) driving the commercial vehicle combination in a normal operating mode by drawing electrical energy at a drive output from the first and / or second electrical storage device, and / or b) providing electrical energy at a recuperation output using the first and / or second electric machine, and supplying the energy to the first and / or second electrical storage device in a recuperation mode.

[0020] In a preferred embodiment of the invention, the operating parameters comprise one, several or all of the following: i) Total capacity of the first and second electrical storage devices, ii) Total charge level of the first and second electrical storage devices, iii) Total drive power of the first and second electric machines, iv) Total recuperation power of the first and second electric machines, v) Maximum drive power of the first electric machine, vi) Maximum drive power of the second electric machine, vii) Maximum (first) recuperation power of the first electric machine, iix) Maximum (second) recuperation power of the second electric machine, ix) Maximum (first) charging power of the first electrical storage device, x) Maximum (second) charging power of the second electrical storage device, xi) Maximum (first) braking power of the first electric machine, and / or xii) Maximum (second) braking power of the second electric machine.

[0021] The maximum recuperation power is limited by the power output of the electric motors on the one hand and by the maximum charging capacity of the respective batteries on the other. For example, if the tractor unit has an electric motor with a maximum power output of 450 kW, then generally no more than 450 kW of recuperation power can be provided. A similar principle applies to the electric motors in the trailer. If, for example, an electric motor with a maximum power output of 250 kW is used there, then only a correspondingly high maximum recuperation power can be achieved.

[0022] The maximum braking power of the electric machines of the commercial vehicle combination is preferably stored in the vehicle control system, in particular in the fuel cell control system.

[0023] Preferably, a set of information elements is provided for the trailer, for example also in the vehicle control system, and / or on or in the tractor unit, by means of which it is apparent to the vehicle control system, in particular to the fuel cell control system, what kind of trailer is attached to the tractor unit, and above all, what kind of electric machine and what kind of electrical storage device is provided by the trailer.

[0024] Preferably, the available braking power is determined from the maximum motor torque that the electric motors can provide at the current motor speed. This information can be transmitted, for example, via a bus system.

[0025] The maximum possible recuperation power can be further limited by the energy storage system. No more recuperation power can be supplied than the maximum charging power the electrical storage system can handle. The maximum possible charging power of the energy storage system depends on the current state of charge and other design-specific battery parameters such as the charging rate (C-rate), the internal resistance of the cells within the energy storage system, etc.

[0026] The total capacity of the energy storage systems and the performance values ​​of the electrical machines, especially the trailer, can be determined, for example, via coded information attached to the trailer, such as barcodes, etc.

[0027] In a preferred embodiment, the generation power is additionally adjusted according to an operating strategy, wherein the operating strategy has a temporal profile. Preferably, the operating strategy includes a prediction of the drive power and / or the recuperation power provided along the time profile. The prediction can therefore, for example, include future changes in the drive power of the first and / or second electric machines, the total drive power, the recuperation power of the first and / or second electric machines, and / or the total recuperation power.

[0028] In a further preferred embodiment, the operating strategy includes a prediction of the charge levels of the first and / or second electrical storage device over time, in particular a prediction of changes in the charge level of the first and / or second electrical storage device occurring over time.

[0029] In a further preferred embodiment, the method comprises the steps of: determining route information over time, and additionally adjusting the generation power depending on the determined route information. The route information can be determined via predefined route profiles, which can be read, for example, from a fleet management system or a topographic cruise control system. From the route information, the vehicle control system for the commercial vehicle combination, for example, using the fuel cell control system, can determine the energy demand over the entire route. A characteristic feature of the invention in this aspect is that the trailer can significantly support the tractor unit by providing additional drive power and additionally extracting energy in recuperation mode.This reduces the required generation power that the fuel cell system must provide. If a trailer with its own energy storage and electric motor were attached to a conventional combustion engine tractor, the additional drive and recuperation power of the trailer would also result in reduced fuel consumption for the tractor, but this would be solely due to the mechanical effect of the trailer assisting the tractor with propulsion and recuperation.

[0030] Unlike internal combustion engines, the fuel cell system operates fundamentally independently of mechanical influences on the tractor, but solely on the basis of the operating parameters of the fuel cell.

[0031] By utilizing the operating parameters of the overall system and, optionally, additional operating parameters from the route information, the fuel cell system can respond appropriately to each specific trailer, which carries its own electric motor and electrical storage, and adjust the amount of power it provides accordingly, i.e., generally reduce it. In the long term, this leads to a better efficiency of the fuel cell system, which can operate more efficiently at lower operating points than at higher ones.By predictively considering route information, the tractor unit can, for example, reduce the power output of the fuel cell system earlier when driving uphill, knowing that the road will then descend for a longer distance and that, in recuperation mode, electrical energy can be supplied by both the first and second electric machines and transferred to the electrical storage, thus relieving the fuel cell system.

[0032] In another preferred embodiment, the operating parameters are determined as follows: The total capacity, total charge level, and / or maximum possible charging power of the first and / or second electrical storage device, as determined by a query from the vehicle's battery management system, along with the operating parameters, are transmitted to the fuel cell controller of the fuel cell system. This transmission can occur via a bus system of the commercial vehicle, such as a CAN bus. In preferred embodiments, transmission via wireless communication, such as radio transmission, between the fuel cell controller and the battery management system is also provided. Wireless transmission can be achieved, for example, via Bluetooth, ISM, or SRD connections. Alternatively, wireless transmission can be achieved via network transmission standards such as WLAN.

[0033] In further preferred embodiments, the trailer is connected to the tractor unit via a dedicated wired LAN line, so-called Automotive Ethernet, and the operating parameter data can be transmitted to the tractor unit and optionally to the fuel cell control unit via this line.

[0034] In preferred embodiments, the battery management system is integrated into the tractor unit or its electronic brake control system, or into an electronic brake control system of the trailer. The electronic brake systems of the tractor unit and the trailer communicate with each other when regulating the braking of the overall system and preferably coordinate both the regenerative braking by the electric motors in recuperation mode and the activation of the friction brakes, or the operation of retarders.

[0035] In another preferred embodiment, the operating parameters are determined as follows: Total capacity of the first and second electrical storage devices, maximum drive power of the first and / or second electric machine, and / or maximum recuperation power of the first and / or second electric machine by reading information elements on the vehicle combination, in particular one or more barcodes.

[0036] In In another preferred embodiment, the total capacity of the first and second electrical storage devices, and / or the total recuperation power of the first and second electric machines, is calculated by the fuel cell control unit, or by a trailer or tractor brake control unit, and transmitted to the fuel cell control unit via data transmission.

[0037] InIn a further preferred embodiment, which is also a second, independent aspect of the invention, the method comprises, preferably in addition to the preferred embodiments described above, or on its own, the following steps: Switching from normal operating mode to recuperation mode at a switching point, and shutting down the generation power of the fuel cell system before the switching point, at the switching point, or within a predetermined (first) delay period after the switching point.

[0038] The first delay duration is preferably in the range of 3.0 seconds or less, and further preferably 2.0 seconds or less.

[0039] InThis aspect of the invention primarily addresses the adjustment of the generation power provided by the fuel cell system in recuperation mode. Due to the limited dynamics of fuel cell systems, as mentioned earlier, they cannot be abruptly reduced from an operating point to a lower power level or switched off during operation without risking damage. Instead, a gradual reduction of the generation power over a certain period is necessary to prevent damage. InAt the point in time when the system switches from a normal operating mode to a recuperation mode, for example when a braking command is received or when a gradient section defined in advance as part of the operating strategy begins, the recuperated energy is usually transferred from both the electric machines to the electrical storage devices and from the fuel cell system at the beginning of the recuperation process.

[0040] However, as explained above, the maximum charging power of the electrical storage system is limited. It is not possible for the electrical storage system to absorb an unlimited amount of electrical energy per unit of time. This maximum charging power is determined, among other things, by the charging rate, also known as the C-rate. A portion of the maximum possible charging power for an electrical storage system is "occupied" by the generation power provided by the fuel cell, meaning that the electric motors sometimes cannot feed their full recuperation power into the electrical storage system. This is where the invention comes in, in this second aspect, by systematically reducing the generation power from the fuel cell system when the vehicle switches from normal operating mode to recuperation mode.

[0041] As part of the operating strategy, it is also preferred if the fuel cell begins to reduce its generated power output even before the switchover point, provided this point is known within the operating strategy. The earlier this reduction step is initiated, the sooner the full recuperation potential of the electric machines in recuperation mode can be utilized.

[0042] At switching points that are not predetermined, but rather triggered by sudden braking requests from the driver or an electronic braking system, this switching point, coinciding with the braking command, is preferably used as a trigger for reducing the generation power. The proportion to which the fuel cell system occupies the maximum charging power of the electrical storage system is thus specifically reduced, so that the first electric motor, and therefore the entire commercial vehicle combination, can fully exploit the recuperation potential.

[0043] In order to provide as much leeway and time as possible for shutting down the fuel cell, the operating strategy in its preferred embodiment is set such that free capacity is already available in the first electrical storage device and / or in the second electrical storage device at the time of switching, the charge level of which is therefore below the respective total capacity of the electrical storage devices, already at the time of switching.

[0044] In a preferred embodiment, from the switching point onwards, recuperation power is initially provided only by the second electric machine, in particular supplied to the second electrical storage device, and only subsequently is recuperation power provided by the first electric machine, in particular supplied to the first electrical storage device. By cascading the recuperation through the electric machines, and initially using only the second electric machine of the trailer in recuperation mode for regenerative braking, the fuel cell system can be gently shut down to relieve the electrical storage devices, and in particular the first electrical storage device, before recuperation by the first electric machine begins.If, in addition to the trailer, the tractor unit with its electric motor also begins to transfer the recuperated energy into the first electrical storage device, the generation power provided by the fuel cell system has already dropped considerably, so that less "bandwidth" of the maximum charging power that can be absorbed by the battery is occupied by the generation power, and can be fed in with a higher recuperation power.

[0045] In principle, the earlier the reduction of the charging power of the fuel cell system begins, the greater the recuperation potential of the two electric machines in recuperation mode and the more time is available to reduce the generation power of the fuel cell system, which positively influences its lifespan.

[0046] In preferred embodiments, the second delay period, i.e. the period from the switching point in which recuperation power is initially provided only by the second electric machine, preferably assigned to the trailer, is in a range of up to 5 seconds, more preferably in a range of up to 2 seconds.

[0047] In further preferred embodiments, the period is in the range of one or more seconds before the switching time.

[0048] In a further preferred embodiment, the vehicle combination has a retarder, and in recuperation mode, from the switching point onwards, recuperation power is initially provided only by the first and / or second electric motor, as in the preferred embodiments described above, in particular until the charge level of the first and / or second electrical storage device has reached a predetermined value, such as its respective maximum capacity, and only then is the retarder activated. If further braking energy is then required because the braking power applied up to that point is insufficient, additional deceleration can be achieved using the friction brakes of the vehicle combination.

[0049] The invention has been described above with reference to the method according to the invention. In a further aspect, the invention relates to a commercial vehicle combination comprising a tractor unit, which includes a first electric machine and a first electrical storage device connected thereto, as well as a fuel cell system connected to the first electrical storage device, which is configured to supply the first electrical storage device with electrical energy at a certain generation power.

[0050] The invention solves the underlying problem in such a commercial vehicle combination by having the first and / or second electric machines configured to drive the commercial vehicle combination in a normal operating mode by drawing electrical energy at a drive power from the first and / or second electrical storage devices, and / or to provide electrical energy at a recuperation power in a recuperation mode and supply it to the first and / or second electrical storage device, and wherein the commercial vehicle combination has a vehicle control system that is connected to the electric machines and the electrical storage devices via signal transmission and is configured to carry out the method according to one of the preferred embodiments described above.

[0051] In particular, the vehicle control system includes a fuel cell control system, wherein the fuel cell control system is configured to control the fuel cell system to provide the generation power, wherein the vehicle control system is configured to a) to control the electric machines for propelling the commercial vehicle combination in a normal operating mode by drawing electrical energy from the electrical storage devices, or b) to control the electric machines for providing electrical energy during recuperation and for supplying the energy to the electrical storage devices in a recuperation mode; and the fuel cell control is configured to determine operating parameters of the first and second electric machines and / or operating parameters of the first and second electrical storage devices; and to control the fuel cell system to adjust the generation power as a function of one, several or all of the determined operating parameters.

[0052] The commercial vehicle combination takes advantage of the same benefits as the inventive method described above. The preferred embodiments of the method are also preferred embodiments of the commercial vehicle combination, and vice versa; therefore, to avoid repetition, reference is made to the above explanations.

[0053] The invention is described in more detail below with reference to the accompanying figures and a preferred embodiment. The figures show: Fig. 1 a schematic representation of a commercial vehicle combination according to a preferred embodiment, Fig. 2 a diagrammatic process sequence according to the prior art for the operation of a commercial vehicle combination, and Figs. 3-6 different diagrammatic process sequences of the method according to the invention.

[0054] In Fig. 1The schematic basic structure of a commercial vehicle combination 100 is shown. The commercial vehicle combination 100 comprises a tractor unit 200 and a trailer 300.

[0055] The tractor 200 has a fuel cell system 1 which is designed to provide electrical energy at a generation power PE.

[0056] The tractor 200 also has a first electrical storage device 3, which is operatively connected to the fuel cell system 1 and is designed to temporarily store the generating power PE provided by the fuel cell system 1.

[0057] The tractor 200 further comprises at least one first electric machine 5, which is operatively connected to the first electrical storage device 3. The at least one first electric machine 5 is configured to drive the tractor 200 in a normal operating mode N by drawing electrical drive energy from the first electrical storage device 3 at a first drive power P A1, and in a recuperation mode R, during so-called regenerative braking, to recover electrical recuperation energy from the moving tractor 200 at a recuperation power P R1 and supply it to the first electrical storage device 3.

[0058] The tractor unit 200 has a vehicle control unit 8, which is configured to control the electronic components of the commercial vehicle combination 100 for its operation. The vehicle control unit 8 preferably has several control units, including a fuel cell control unit 7, which is configured to control the fuel cell system 1. The fuel cell control unit 7 is shown here as a separate unit, but could also be structurally integrated into another component, in particular the fuel cell system 1. The fuel cell control unit 7 is configured to adjust the amount of power PE provided by the fuel cell system 1 by controlling the fuel cell system 1.

[0059] The commercial vehicle combination 100 has, in addition to the first electrical storage device 3 arranged in the tractor unit 200, at least one second electrical storage device 9, which is assigned to the trailer 300. Furthermore, the trailer 300 has at least one second electric motor 11, which is operatively connected to the second electrical storage device 9.

[0060] The second electric machine 11 is configured to operate in a normal operating mode N, cf. Figs. 2 to 6 , to drive the trailer 300 by extracting electrical energy at a drive power P A2, and in a recuperation mode R, cf. Figs. 2 to 6 , to recover electrical energy at a recuperation power P R2 from the moving trailer 300 and supply it to the second electrical storage device 9.

[0061] When the tractor unit 200 and the trailer 300 are coupled, the commercial vehicle combination 100 is driven, at least temporarily in normal operating mode N, by both the first electric motor 5 and the second electric motor 11. A total drive power PAG = PA1 + PA2 is available for this purpose. In recuperation mode R, energy can be recovered analogously from both the first electric motor 5 and the second electric motor 11, with a total recuperation power PRG = PR1 + PR2, where PR1 is contributed by the tractor unit 200 and PR2 by the trailer 300.

[0062] The fuel cell control unit 7 is connected to the electrical storage units 3, 9 and to the electrical machines 5, 11 via signal transmission and is configured to receive representative data for electrical operating parameters B of the electrical storage units 3, 9 and / or the electrical machines 5, 11.These operating parameters include a capacity K1 of the first electrical storage device 3, a capacity K2 of the second electrical storage device 9, a charge level L1 of the first electrical storage device 3, a charge level L2 of the second electrical storage device 9, the drive powers PA1 and PA2 of the electrical machines 5, 11, the recuperation powers PR1, PR2 of the electrical machines 5, 11, maximum drive powers PA1max and PA2max, maximum recuperation powers PR1max and PR2max of the electrical machines 5, 11, maximum charging powers PL1max, PL2max of the electrical storage devices 3 and 9 and / or the maximum braking powers PB1max, PB2max of the electrical machines 5, 11.

[0063] The vehicle control unit 8 preferably further comprises a brake control unit 17, which in turn may have several control units (not shown individually), such as a tractor brake control unit (EBS) assigned to the tractor unit 200 and a trailer brake control unit (TEBS) assigned to the trailer 300. For a better understanding of the invention, only brake control unit 17 is shown by way of example. Figure 1 As shown, the vehicle control unit 8 is set up to control the electric machines 5, 11 in normal operating mode N to drive the commercial vehicle combination 100 and in recuperation mode R to generate electrical energy at a recuperation power P R1 or P R2 and to use, for example, the brake control unit 17 for this purpose.

[0064] In particular, the fuel cell control 7 is designed to control the fuel cell system 1 as a function of the determined electrical operating parameters B in such a way that the generation power PE is adjusted depending on the determined operating parameters B.

[0065] The fuel cell control unit 7 can be directly connected to the electrical storage units 3, 9 via signal transmission to determine the electrical operating parameters B, as well as alternatively or additionally via signal transmission to a battery management system 15, which is part of the vehicle control unit 8 and is in turn connected via signal transmission to the electrical storage units 3, 9 and is configured to receive the individual operating parameters B from the electrical storage units 3, 9, and either calculate them individually or together and transmit them to the fuel cell control unit 7.

[0066] Optionally, the commercial vehicle combination 100 has one or more retarders 19, and the vehicle control unit 8 is configured to control this for the execution of a continuous braking function, for example controlled by the brake control unit 17.

[0067] The inventive method described above in more general terms is used in the operation of the commercial vehicle combination 100. In an exemplary operating sequence, the commercial vehicle combination 100 is moved in a normal operating mode N. The fuel cell system 1 generates electrical energy at a generation power PE. The energy provided with the generation power PE is temporarily stored in the first electrical storage device 3, so that it is at a charge level L1 which is equal to or less than the maximum capacity K1 of the electrical storage device 3. PE can be less than or equal to the maximum charging power P L1max. The first electric machine 5 provides the drive power P A1 by drawing electrical energy from the electrical storage device 3, with which the tractor unit 200 is driven.

[0068] The second electric machine 11 provides the drive power P A2 by drawing electrical energy from the second electrical storage device 9, where the drive power P A2 is less than or equal to the maximum drive power P A2max of the second electric machine 11. This drive energy P A2 is used to drive the trailer 300, so that the total drive power P AG of the commercial vehicle combination 100 is equal to P A1 + P A2.

[0069] If you do this at a switching point, see: Figs. 2 to 6When the vehicle combination 100 switches from normal operating mode N to recuperation mode R, for example when descending a slope and / or braking, the electric machines 5 and 11 are controlled as generators. This process is known as regenerative braking or recuperation. In this recuperation mode R, the first electric machine 5 generates electrical energy at a recuperation power PR1 and supplies it to the first electrical storage device 3, while the second electric machine 11 makes the recuperation power PR2 it provides available to the second electrical storage device 9.

[0070] During the operation of the commercial vehicle combination 100, both in normal operating mode N and in recuperation mode R, the fuel cell control 7 determines the operating parameters B described above from the electrical storage devices 3, 9 and the electrical machines 5, 11 and adjusts the generating power PE of the fuel cell system 1 as a function of the operating parameters B.

[0071] For example: The more recuperation power P R1 can be provided by the first electric machine 5, the further the generation power PE can be reduced in order to still maintain the first electrical storage device 3 at a sufficient charge level L 1 for operating the commercial vehicle combination 100. In addition, the second electric machine 11 reports to the fuel cell control 7, via the operating parameters B, the proportion with which the trailer 300 contributes to the propulsion of the commercial vehicle combination 100 in normal operating mode N, or the proportion with which the trailer 300 contributes to energy recovery via the recuperation power P R2 in recuperation mode R.

[0072] Some operating parameters B of the trailer 300 cannot be determined during operation, but relate to characteristic operating variables that are characteristic of the electric machine 11 and the electric storage device 9 of the trailer 300, for example the capacity K 2 of the second electric storage device 9 installed in the trailer 300, but optionally also the maximum charging power P L2max of the second storage device 9 or the maximum drive power P A2max of the second electric machine 11. These operating parameters can be stored as fixed parametric values ​​in the trailer 300 and transmitted to the fuel cell control unit 7, for example via data exchange.The information elements can, for example, also be assigned to an information element 21, which is arranged, for example, as an RFID element in the coupling area of ​​the trailer 300 towards the tractor 200, or in the form of one or more barcodes that are placed on the trailer 300 and are read when the trailer 300 is connected to the tractor 200.

[0073] The fuel cell controller 7 preferably additionally controls the fuel cell system 1 by means of an operating strategy S(t) along a time course (t), wherein the operating strategy S(t) further preferably includes a prediction of the drive power and / or the recuperation power along the time course. The operating strategy S(t) also preferably includes a prediction of the charge levels L1, L2 of the electrical storage devices 3, 9 along the time course (t).The fuel cell control unit 7 determines route information T for the operation of the commercial vehicle combination 100 either in advance or continuously during normal operating mode N and / or recuperation mode R, from the vehicle control unit 8, for example from a fleet management system of the tractor unit 200 or from a topographic navigation system, and adjusts the generation power PE in addition to taking into account the operating parameters B depending on the determined route information T.

[0074] The fuel cell control 7 queries the operating parameters B: total capacity KG = K 1 + K 2 ; and / or maximum charging power P Lmax = P L1max + P L2max either directly from the electrical storage devices 3, 9 and / or by querying the battery management system 15.

[0075] The total capacity KG, the total drive power P AG, and / or the total recuperation power P RG can be calculated by the fuel cell control 7 or calculated separately, for example by the brake control 17 or the battery management system 15, and transmitted to the fuel cell control 7 by means of data transmission.

[0076] The following section will focus on a specific procedural aspect based on the Figures 2 to 6 discussed in more detail.

[0077] In Fig. 2The operation of a commercial vehicle according to the state of the art is schematically depicted. The commercial vehicle according to the state of the art has a fuel cell system that operates with a constant generating power PE of approximately 90 kW. This power is roughly required to move a fully loaded commercial vehicle combination of approximately 40 tons on a level road at a speed of approximately 80 km / h. It is assumed, for example, that the electrical storage system of the commercial vehicle according to the state of the art has a traction battery with a capacity of 120 kWh. At a charging rate of 1.5 C, this battery could be charged with a maximum charging power P Lmax of 180 kW.However, because the fuel cell system already constantly feeds energy into the electrical storage with a generation power of 90 kW PE, only the difference between the maximum charging power P Lmax and the generation power PE is available as recuperation power PR for a recuperation that begins at a switching point tu, i.e. 90 kW.

[0078] In contrast, the invention relies on adjusting the generating power PE. Applied to a generic setup, initially without distinguishing between tractor and trailer, as illustrated in Fig. 3At a switching point tu, the system switches from normal operating mode N to recuperation mode R, and the commercial vehicle's battery is supplied with electrical energy in addition to the generation power PE and recuperation power PR until the maximum charging power P Lmax is reached. As long as PE remains unchanged at 90 kW, a recuperation power higher than 90 kW cannot be achieved. However, after a delay t 1 of approximately half a second following the switching point tu, the fuel cell system is controlled to reduce the generation power PE. This allows the recuperation power PR to be further increased.

[0079] In the idealized example of the Fig. 3In the following figures, the generating power PE is reduced to 0, which would be equivalent to switching off the fuel cell system. In practical applications, the power PE is preferably set to a reduced power level greater than 0, which is advantageous for the wear behavior and service life of the fuel cell system. In principle, however, a complete shutdown of the fuel cell system and thus a reduction of PE to 0 is also possible.

[0080] The basic principle in Fig. 3 The concept presented is in Fig. 4 more detailed with the addition of a visualization of the operation of both electrical storage units 3, 9 of the commercial vehicle combination 100 according to Fig. 1shown. The second electrical storage unit 9 of the trailer 300, for example, has a capacity K2 of 40 kWh at a C-rate of 6C, resulting in a maximum charging power of the second electrical storage unit 9 of 240 kW (PL2max). In this embodiment, the commercial vehicle combination 100 could therefore receive a maximum recuperation power PR2max of the same magnitude from the second electric machine 11, and consequently a total recuperation power PRGmax of 330 kW, if the fuel cell system 1 were operated constantly at PE = 90 kW. By adjusting the generation power PE, the maximum extractable recuperation power PRGmax is further optimized as follows: As in Fig. 3 At time tu, the system switches from normal operating mode N to recuperation mode R. The second electric machine 11 immediately begins recuperation at time tu and provides the recuperation power P R2.

[0081] After a time interval t2, the first electric machine 5 also begins to provide recuperation power PR1. From time tu onwards, the fuel cell system 1 is controlled in such a way that the generation power PE is (gently) reduced. Thus, after the time interval t2 has elapsed, a greater recuperation power PR1 can be provided by the first electric machine 5 than would be possible if the maximum charging power PL1max of the first electric machine 5 had not been reduced. In this way, the maximum achievable total recuperation power PRGmax is successively optimized.

[0082] As can already be seen from the comparison of the preceding figures, it is advantageous for maximizing the recuperation potential of the commercial vehicle combination 100 to reduce the generation power PE as early as possible within the framework of the operating strategy S(t) at a known upcoming switching time tu, i.e. even before the switching time tu.

[0083] The invention is also advantageous if the generating power PE is only reduced after the switching time tu, as Fig. 5 Illustrated by example.

[0084] In the Fig. 5In the diagrammatically outlined process sequence, during normal operating mode N, the fuel cell system 1 is controlled to provide a constant generation power PE, where PE is below the maximum charging power P L1max of the first electrical storage unit 3. At the switching point tu, the system switches to recuperation mode R, and at the same time, the second electric machine 9 begins to provide the recuperation power P R2. With a delay of t 1 after the switching point tu, the fuel cell system 1 is then controlled to reduce the generation power PE. At the same time, the first electric machine 5 begins to provide the recuperation power P R1.The increase in recuperation power PR1 slows down the moment the charging power PL1 reaches its maximum PL1max, but continues to rise due to the ongoing adjustment of the generation power PE until, in this embodiment as well, the maximum total recuperation potential PRGmax can finally be fully utilized after a few seconds. As in the embodiment of the... Fig. 4 There is a period t 2 between the start of recuperation by the second electric machine 11 and the first electric machine 5.

[0085] In the event that, despite the full utilization of a maximum recuperation power P RGmax =P R1max +P R2max, additional braking effect is still required during a deceleration process in recuperation mode R, the retarder 19 can be additionally controlled by the vehicle control 8 or brake control 17 after the recuperation potentials have been fully utilized, and if this is also insufficient to decelerate the commercial vehicle combination 100, the friction brakes can subsequently be additionally controlled.

[0086] In contrast to the embodiment according to Fig. 5 is described in the exemplary procedure according to Fig. 6 The recuperation process does not begin in a cascaded manner from the switching point tu, but rather simultaneously at the switching point tu, so that in comparison to Fig. 5 the increase in total recuperation power P RG is steeper than in the variant according to Fig. 5The reduction of the generation power PE begins within the delay period t1 after the switchover time, in this case approximately 1 second. The attenuation of the increase in the total recuperation power PRG starts earlier and is then somewhat flatter than in the process sequence according to Fig. 5 , but ultimately the same maximum total recuperation power P RGmax is achieved as in Fig. 5 reached.

[0087] As can be seen from the above, the application of the principles of the invention leads to a reduced generation power PE and thus to a lower reactant consumption in the operation of the fuel cell system 1. In addition, this improved utilization of the recuperation potentials of the electric machines allows energy to be recovered in the operation of the commercial vehicle combination 100, and the wear of the friction brakes of the commercial vehicle combination 100 can be reduced. REFERENCE SIGN LIST (PART OF THE DESCRIPTION)

[0088] 1 Fuel cell system 3 First electrical storage 5 First electric machine 7 Fuel cell control 8 Vehicle control 9 Second electrical storage 11 Second electric machine 15 Battery management system 17 Brake control 19 Retarder 21 Information element 100 Commercial vehicle combination 200 Tractor unit 300 Trailer B Operating parameters K1, K2 Capacity of first / second electrical storage KG Total capacity L1, L2 State of charge of first / second electrical storage N Normal operating mode PA1, PA2 Drive power of first / second electric machine PA1max, PA2max Maximum drive power of first / second electric machine PAG Total drive power PB1max, PB2max Maximum braking power of first / second electric machine PE Generation power (fuel cell system) PL1max, PL2max Maximum charging power, first electrical storage PR, (PR1, PR2 )Recuperation power,(first / second electrical storage) P R1max , P R2max maximum recuperation power, first / second el.Machine P RG Total recuperation power P RGmax Maximum total recuperation power RRecuperation mode S(t)Operating strategy TRoute information (t)Time course tuSwitching time.

Claims

1. Method for operating a commercial vehicle combination (100) comprising - a tractor (200) having a first electric machine (5), a first electric storage device (3) operatively connected thereto, and a fuel cell system (1) which is operatively connected to the first electric storage device (3) and configured to provide electrical energy at a generation power (PE), - a trailer (300) having a second electric machine (11) and a second electric storage device (9) operatively connected thereto, wherein the method comprises the steps of: - determining operating parameters (B) of the first electric machine (5) and the second electric machine (11) and determining operating parameters (B) of the first electric storage device (3) and / or the second electric storage device (9); and the method characterized by the steps of: - adjusting the generation power (PE) of the fuel cell system (1) as a function of a plurality of or all of the determined operating parameters (B), - providing the generation power (PE) by means of the fuel cell system (1), and a) driving the commercial vehicle combination (100) in a normal operating mode (N) by drawing electrical energy at a drive power (PA1, PA2) from the first electric storage device (3) and / or the second electric storage device (9), and / or b) providing electrical energy at a recuperation power (PR1, PR2) by means of the first electric machine (5) and / or the second electric machine (11), and supplying the energy to the first electric storage device (3) and / or the second electric storage device (9) in a recuperation mode (R).

2. Method according to claim 1, wherein the operating parameters (B) comprise one, a plurality of or all of the following: i) total capacity (KG) of the first electric storage device (3) and of the second electric storage device (9), ii) total charge level (LG) of the first electric storage device (3) and of the second electric storage device (9), iii) total drive power (PAG) of the first electric machine (5) and of the second electric machine (11), iv) total recuperation power (PRG) of the first electric machine (5) and of the second electric machine (11), v) maximum first drive power (PA1max) of the first electric machine (5), vi) maximum second drive power (PA2max) of the second electric machine (11), vii) maximum first recuperation power (PR1max) of the first electric machine (5), iix) maximum second recuperation power (P R2max) of the second electric machine (11), ix) maximum first charging power (PL1max) of the first electric storage device (3), x) maximum second charging power (PL2max) of the second electric storage device (9), xi) maximum first braking power (PB1max) of the first electric machine (5), and / or xii) maximum second braking power (PB2max) of the second electric machine (11).

3. Method according to either of the preceding claims, wherein the generation power (PE) is adjusted according to an operating strategy S(t), wherein the operating strategy S(t) has a temporal profile (t).

4. Method according to claim 3, wherein the operating strategy S(t) has a prediction of the drive power (PAG, PA1, PA2) and / or of the recuperation power (PRG, PR1, PR2) along the temporal profile (t).

5. Method according to either of claims 3 or 4, wherein the operating strategy S(t) has a prediction of the charge level (L1) of the first electric storage device (3) and / or of the charge level (L2) of the second electric storage device (9) along the temporal profile (t), in particular a prediction of changes of the charge level (L1) of the first electric storage device (3) and / or of the charge level (L2) of the second electric storage device (9) occurring along the temporal profile (t).

6. Method according to any of claims 3 to 5, comprising the steps of: - determining route information (T) along the temporal profile (t), and - adjusting the generation power (PE) additionally depending on the determined route information (T).

7. Method according to any of the preceding claims, wherein the operating parameters (B) total capacity (KG), total charge level (LG) and / or maximum possible charging power (PL1max, PL2max) of the first and / or the second electric storage device (3, 9) are determined by querying a battery management system (15), and the operating parameters (B) are transmitted to a fuel cell control unit (7, 17) of the fuel cell system (1).

8. Method according to any of the preceding claims, wherein the operating parameters (B) total capacity (KG) of the first electric storage device and of the second electric storage device (3, 9), maximum drive power (PA1max) of the first electric machine (5) and / or maximum drive power (PA2max) of the second electric machine (11), and / or maximum recuperation power (PR1max, PR2max) of the first and / or the second electric machine (5, 11) are determined by reading information elements (21) on the commercial vehicle combination (100).

9. Method according to any of the preceding claims, wherein the total capacity (KG) of the first and the second electric storage (3, 9), and / or the total recuperation power (PRG) of the first electric machine (5) and the second electric machine (11) is calculated by a fuel cell control unit (7, 17).

10. Method according to any of the preceding claims 3 to 9, comprising: - switching from normal operating mode (N) to recuperation mode (R) at a switching time (tu), and - shutting down generation power (PE) before the switching time (tu), at the switching time (tu) or within a predetermined initial delay period (t1) after the switching time (tu).

11. Method according to claim 10, wherein the generation power (PE) is controlled such that the total charge level (LG) of the first and the second electric storage device (3, 9) is below the total capacity (KG) at the switching time (tu).

12. Method according to claim 11, wherein, from the switching time (tu), recuperation power (PR2) is initially provided by only the second electric machine (11) for a second delay period (t2) and in particular supplied to the second electric storage device (9), and only subsequently is recuperation power (PR1) provided by the first electric machine (5) and in particular supplied to the first electric storage device (3).

13. Method according to claim 11 or 12, wherein the second delay duration (t2) from the switching time (tu), in which recuperation power (PR2) is initially provided by only the second electric machine (11), is in a range of 5.0 s or less, preferably in a range of 2.0 s or less.

14. Method according to any of claims 10 to 13, wherein the commercial vehicle combination (100) has a retarder (19), and in recuperation mode (R), from the switching time (tu), recuperation power (PR1, PR2) is initially provided by only the first electric machine (5) and / or the second electric machine (5, 11), and only subsequently is the retarder (19) activated.

15. Method according to any of claims 3 to 9, wherein the commercial vehicle combination (100) has a retarder (19), and a shutdown of the generation power (PE) is initiated by means of the fuel cell system (1) by activating the retarder (19).

16. Commercial vehicle combination (100) comprising a tractor (200) having a first electric machine (5) and a first electric storage device (3) operatively connected thereto, a trailer (300) having a second electric machine (11) and a second electric storage device (9) operatively connected thereto, and a fuel cell system (1) arranged on the tractor (200), which is operatively connected to the first electric storage device (3) and is configured to provide electrical energy at a generation power (PE), wherein the first and the second electric machine (5, 11) are configured to drive the commercial vehicle combination (100) in a normal operating mode (N) by drawing electrical energy at a drive power (PA1, PA2) from the first and / or the second electric storage device (3, 9), and in a recuperation mode (R), to provide electrical energy at a recuperation power (PR1, PR2) and to supply electrical energy to the first and / or the second electric storage device (3, 9); the commercial vehicle combination (100) characterized in that it has a vehicle control unit (8), which is connected in a signal-conducting manner to the electric machines (5, 11) and the electric storage devices (3, 9), and is configured to carry out the method according to any of the preceding claims.