Method for operating an electric vehicle and electric vehicle

Abstract

The present invention relates to a method for operating an electric vehicle and an electric vehicle, the electric vehicle comprising: an electric travel drive for the vehicle's travel movement; a control device for controlling the vehicle's travel movement; a first energy storage device for supplying a first DC voltage to the control device; a second energy storage device for supplying a second DC voltage to the travel drive, the second DC voltage being in particular greater than the first DC voltage; and an energy supply unit, the energy supply unit in particular providing a DC output voltage intermittently; wherein the first energy storage device is connected to the energy supply unit via a conversion device, wherein the second energy storage device is connected to the energy supply unit, wherein the conversion device converts the DC output voltage into a first DC voltage, in particular wherein the first DC voltage is less than the DC output voltage, wherein a first power flow from the first energy storage device to the second energy storage device is prevented, and a second power flow from the second energy storage device to the first energy storage device is prevented.

Description

Technical Field

[0001] The invention relates to a method for operating an electric vehicle and an electric vehicle. Background Art

[0002] Preferably, the driverless, mobility assistance system is provided as an electric vehicle. Alternatively, such a vehicle may also be referred to as an unmanned transport vehicle (FTF) or AGV (English: automated guided vehicle, automatic guided vehicle).

[0003] DE 10 2007 002 242 A1 discloses an unmanned transport vehicle for transporting loads. Such transport of loads can be referred to as an intralogistics application. The unmanned transport vehicle is supplied with energy inductively.

[0004] DE 195 45 544 A1 discloses a ground conveyor system in which the vehicles are supplied with electrical energy via a power line. In order to be able to operate the vehicles even without an external energy source, it is proposed to use electrolytic or gold capacitor storage devices (also known as supercapacitors, farad capacitors or double-layer capacitors) as a source of electrical energy.

[0005] A supercapacitor energy supply for an electric vehicle is known from US Pat. No. 6,265,851 B1, which has two energy storage devices that can be used selectively to drive the vehicle.

[0006] An unmanned transport system is known from EP 2 419 364 A1, which has two energy storage devices (a double-layer capacitor device and a battery device). In normal operation, the double-layer capacitor device supplies energy to the drive unit, i.e. the motor. In an emergency, i.e. when the voltage in the double-layer capacitor device drops below a certain level, it switches to battery operation. Then, the drive unit is only supplied with energy by the battery device until the double-layer capacitor device is recharged at a charging station.

[0007] DE 10 2017 005 153 A1 discloses a method for operating an electric vehicle and an electric vehicle, wherein the vehicle has a hybrid storage device and a double-layer capacitor device. Both storage devices can selectively supply energy to a traction drive.

[0008] No. 5,793,189 discloses a device for protecting a battery used in an electric vehicle from excessive discharge. Summary of the invention

[0009] It is therefore an object of the present invention to improve and simplify the energy management of an electric vehicle, in particular of an unmanned mobility assistance system, which has two different types of energy storage devices.

[0010] The important feature of the present invention in the method for operating an unmanned mobility assistance system (MAS) for electric vehicles, especially for applications in internal logistics, is that the vehicle has: an electric travel drive for driving movement of the vehicle, especially traction; a control device for controlling the driving movement of the vehicle; a first energy storage device, the first energy storage device is especially designed as a rechargeable battery device, the first energy storage device is used to supply a first DC voltage to the control device; a second energy storage device, the second energy storage device is especially designed as a double-layer capacitor device, and / or the second energy storage device is especially charged and discharged faster than the first energy storage device, the second energy storage device is used to supply a second DC voltage to the travel drive, the second DC voltage is especially greater than the first DC voltage; and an energy supply unit, the energy supply unit especially intermittently provides a DC output voltage, wherein the first energy storage device is connected to the energy supply unit via a conversion device,

[0011] The second energy storage device is connected to the energy supply unit.

[0012] wherein the conversion device converts the DC output voltage into a first DC voltage, in particular wherein the first DC voltage is less than the DC output voltage, wherein a first power flow from the first energy storage device to the second energy storage device is prevented, and

[0013] A second power flow from the second energy storage device to the first energy storage device is prevented.

[0014] Advantageously, the use of the two energy storage devices is separate. The second energy storage device provides the required drive energy, while the first energy storage device provides energy for the control device. The second energy storage device is usually used almost completely when driving, and is recharged during the rest of the logistics process. The capacity of the second energy storage device can be matched to the needs of the logistics process, and basically depends on the driving distance when there is no external energy supply, that is, when the energy supply unit does not provide power. Therefore, when the driving distance is known, the capacity of the second energy storage device can be selected accordingly and matched to the requirements in the best way. Although the first energy storage device is also charged during the logistics break, it is designed to supply its energy to the control electronics for a longer time. Therefore, the capacity of the second energy storage device can be matched to the needs of the logistics process, and it does not only depend on the driving time without external energy supply, but is mainly determined by the following method, that is, what kind of unforeseen interference occurs in the logistics process and causes the vehicle to stagnate. Interference may be, for example, an unexpected obstacle or person on the driving distance, but it may also be a delay associated with other processes that are not yet ready. Therefore, decoupling these energy storage devices can be achieved for the corresponding electrical consumers to carry out targeted storage design. Thus, for example, for the use of a mobility assistance system with a long parking time, the second energy storage device only needs to be designed for the driving (distance). In particular, during the entire process, the energy supply for the control electronics is taken over by the first energy storage device, which is advantageously designed for the longest expected time until the next charging.

[0015] Advantageously, the first energy storage device has a higher energy density and thus in practice a lower power density and a lower number of possible charge / discharge cycles than the second energy storage device. Advantageously, the second energy storage device can be charged and discharged faster than the first energy storage device.

[0016] The first energy storage device is advantageously designed as a battery device. An example of a battery device is an assembly consisting of one or more secondary electrochemical elements, which are especially nickel- and / or iron-based. Such secondary electrochemical elements include a negative electrode, a positive electrode, a porous separator separating the negative and positive electrodes from each other, and an especially aqueous alkaline electrolyte with which the electrodes and the separator are impregnated. Such nickel- and / or iron-based secondary electrochemical elements can deliver high pulse currents very quickly, like capacitors, but they otherwise behave more precisely like batteries, and the capacitor equations Q=CU and W= 1 / 2C U 2. Such a battery device has a higher cycle stability. The cycle stability is between 1000 and 20000, so that charging and discharging cycles can be performed more frequently before the power standard of the battery device is no longer met. In addition, the battery device has overcharge stability and deep discharge stability. It can be quickly charged at up to 15C. Nevertheless, the charging and discharging speed of the battery device will be slower than that of the double-layer capacitor device, which is an advantageous design for the second energy storage device. The double-layer capacitor device is characterized in that it can be charged and completely discharged to zero voltage within a few seconds. Its cycle stability is in the range of one million times.

[0017] In an advantageous design, the first power flow is blocked at any time, i.e. at any point in time, and the second power flow is blocked at any time, i.e. at any point in time. This statement should be understood as follows, that the method is implemented in such a way that the transfer of charge or energy between the two energy storage devices is blocked not only intermittently but also permanently, i.e. at any time. Therefore, it is impossible to use the charge or energy once stored in one energy storage device for charging the other energy storage device at any time. Advantageously, the use of the two energy storage devices is completely separated at any time. The second energy storage device only provides the required drive energy at any time, while the first energy storage device only provides energy for the control device at any time. As will be further disclosed below, the blocking of the second power flow can be achieved at least by means of structural components, such as diodes or by means of regulation technology measures.

[0018] In an advantageous embodiment, the output current of the energy supply unit has a value which is substantially constant over time, in particular, the output current is regulated to this constant value. It is thus possible to charge the second energy storage device with a constant current until a fixed maximum voltage is reached, in particular, the energy supply unit is subsequently deactivated, i.e. when the maximum voltage is present at the second energy storage device. Advantageously, the energy supply unit can be controlled very simply. In particular, the output current can be regulated / controlled to a constant value.

[0019] In an advantageous embodiment, the energy supply unit delivers energy in a contact-free or contact-free manner.

[0020] In this case, the advantage in the case of contact-based energy transmission is that the energy storage device can be easily charged, for example by means of a plug connection.

[0021] The advantage of contactless energy transmission is that the energy storage device can be safely charged, for example by induction. In an advantageous embodiment, the energy supply unit comprises a rectifier which is fed by the secondary inductance of the electric vehicle, in particular a capacitor is connected in series or in parallel with the rectifier, so that the resonant frequency of the oscillating circuit formed thereby is equal to the frequency of the alternating current entering the fixedly arranged primary inductance. Due to the inductive energy transmission, safety is also increased, and the wear of the charging contacts which would otherwise be necessary does not occur. In addition, a contact-safe implementation can be easily realized.

[0022] In an advantageous embodiment, energy is supplied to the energy supply unit intermittently during driving.

[0023] It is advantageous here that the energy supply can be implemented over a partial area of ​​the driving distance, and thus the two energy storage devices can either be recharged or their charge state can remain fully charged and thus their service life can be extended, because they are subject to as few complete charging cycles as possible, in particular because they are not frequently fully charged and discharged. Aging is thus reduced. For example, the energy supply can be implemented in a contact-type manner by means of a power supply line. Alternatively, a fixedly arranged primary conductor is arranged along the driving distance, via which the energy is inductively transmitted to a secondary inductor arranged in the electric vehicle.

[0024] In an advantageous embodiment, the first power flow is prevented in that the converter device is designed as a unidirectional, in particular potential-isolating, DC / DC converter.

[0025] It is advantageous here that the first power flow can be blocked in a simple manner while the voltage transformation is being carried out. The advantage of a potential-isolated DC / DC converter is that the two voltage levels U0 and U2 are electrically isolated and thus enable electrically safe isolation of the drive supply and the electronics supply. Since only one power flow direction is provided, simple and inexpensive electronic circuits can be used despite the potential isolation. This is not possible in a bidirectional circuit.

[0026] In an advantageous refinement, the second power flow is prevented by a diode arranged between the second energy storage device and the converter device.

[0027] An advantage here is that preventing the second power flow is easily achievable.

[0028] In a preferred embodiment, the second energy storage device is directly connected to the energy supply unit and / or directly connected to the conversion device, wherein the second power flow is prevented in the following manner, namely, the second DC voltage is monitored by means of gradient evaluation, wherein, in the case of a voltage level of the second DC voltage having a positive gradient, in particular when the second DC voltage is greater than a minimum voltage value, the conversion device is activated, and in the case of a voltage level of the second DC voltage having a non-positive gradient, the conversion device is deactivated.

[0029] Advantageously, no additional electronic circuit or other component is required to control or prevent power flow between the energy supply unit and the second energy storage device and / or between the conversion device and the second energy storage device, such as a diode or switch to prevent round-trip charging between the energy storage devices. This is the meaning of "direct connection". Therefore, "direct connection" does not exclude the arrangement of a resistor or inductor between the second energy storage device and the energy supply unit or the conversion device. The power flow is only prevented by the conversion device and can be simply controlled there. The positive voltage gradient here means that the second DC voltage is increased. On the one hand, the voltage can be increased in the following way, that is, the external energy supply unit feeds energy. On the other hand, energy can also be fed back by the electric motor of the generator-type operation of the driving drive device. Therefore, in this embodiment, it is possible that the first energy storage device is charged by the drive motor of the generator operation, for example, during the braking process of the vehicle. However, it is necessary to ensure that the charging is not carried out under the condition of using the energy stored in the second energy storage device. The voltage level of the second DC voltage is a non-positive gradient, which means that the second DC voltage drops and thus obtains energy from the second energy storage device. Since the conversion device is deactivated in this case, it is ensured that the energy of the second energy storage device is used exclusively to supply the traction drive and, in particular, not to charge the first energy storage device.

[0030] Alternatively, it is also possible to use the described gradient evaluation even though the second energy storage device is not directly, i.e. indirectly, for example via a diode, connected to the energy supply unit or indirectly connected to the conversion device. Therefore, the "direct connection" and "gradient evaluation" features are not inseparably linked to each other. The gradient evaluation only advantageously enables direct connection.

[0031] In an advantageous embodiment, the first DC voltage for charging the first energy storage device is varied, in particular by means of the control device.

[0032] It is advantageous here that the first energy storage device can be charged with a current which can be adjusted precisely, for example according to a charging characteristic curve.

[0033] In an advantageous embodiment, the second energy storage device is designed to receive more current than can be provided by the energy supply unit.

[0034] The advantage here is that the energy supply unit can be protected very easily against overload. For this purpose, only a voltage limiter is required, which will deactivate the energy supply unit when the maximum permissible operating voltage of the second energy storage device is reached.

[0035] The important features of the device according to the invention for supplying a first DC voltage to a first electrical consumer of an unmanned mobility assistance system of an electric vehicle, in particular for intralogistics applications, and for supplying a second electrical consumer with a second DC voltage are: the device comprises: a first energy storage device, which is in particular designed as a rechargeable battery energy storage device; a second energy storage device, which is in particular designed as a double-layer capacitor device and / or the second energy storage device can be charged and discharged faster than the first energy storage device; and an energy supply unit, which can in particular intermittently obtain a DC output voltage, wherein the first DC voltage can be obtained from the first energy storage device, wherein the second DC voltage can be obtained from the second energy storage device, and the second DC voltage is in particular greater than the first DC voltage, wherein the first energy storage device is connected to the energy supply unit via a conversion device, wherein the second energy storage device is connected to the energy supply unit, wherein the conversion device converts the DC output voltage into a first DC voltage, in particular wherein the first DC voltage is less than the DC output voltage, wherein the device is designed to prevent a power flow from the first energy storage device to the second energy storage device and to prevent a second power flow from the second energy storage device to the first energy storage device.

[0036] The advantage here is that the energy storage device can be disconnected and thus a targeted storage configuration can be achieved for the respective electrical load.

[0037] In an advantageous embodiment, the energy supply unit is designed as a controllable / adjustable current source.

[0038] An advantage here is that this aspect is very easy to implement, in particular for inductively coupled energy supply units.

[0039] In an advantageous embodiment, the first energy storage device is arranged on the electric vehicle in a detachable manner, ie, the first energy storage device can be replaced.

[0040] It is advantageous here that the first energy storage device can be easily replaced when it is worn out. The first energy storage device is therefore not firmly mounted or integrated in the vehicle, but is mounted on the vehicle in a releasable manner. In particular, in applications where low voltages are used for the first DC voltage, the advantage is that the first energy storage device can also be easily replaced by personnel who have not received corresponding training. This is particularly advantageous when the first energy storage device is not designed for the service life of the vehicle and is therefore a wearing part.

[0041] In an advantageous embodiment, overvoltage protection and / or undervoltage protection and / or overcurrent protection are provided on the first energy storage device by means of current measurement and / or voltage measurement, and / or overheating protection is provided on the first energy storage device by means of temperature measurement, and / or overvoltage protection and / or overcurrent protection are provided on the second energy storage device by means of current measurement and / or voltage measurement, and / or overheating protection is provided on the second energy storage device by means of temperature measurement.

[0042] The advantage here is that the safety of the energy storage device is increased and the energy storage device cannot be damaged. This is particularly important when energy is fed back to the energy storage device via electrical consumers.

[0043] In an advantageous embodiment, the electric vehicle has a device according to the invention for supplying power to a first and a second electrical consumer of the electric vehicle, wherein the first electrical consumer is a control device for controlling the driving movement of the vehicle and / or the second electrical consumer is an electric driving drive or a lifting device or a transport device for the driving movement of the vehicle, in particular traction.

[0044] It is advantageous here if the control device on the one hand and the controlled electrical consumers on the other hand each have their own energy supply.

[0045] The present invention is not limited to the claimed feature combinations. For those skilled in the art, other reasonable combinations of the features described in this application can be obtained, especially from the purpose proposed and / or by comparing with the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematically shown in FIG is a device according to the invention for supplying voltage to two electrical consumers of a mobility assistance system. A mobility assistance system is also referred to as MAS in the following text;

[0047] Figure 2 Schematically shows a mobility assistance system according to the invention with two electrical consumers;

[0048] Figure 3 A further embodiment of a mobility assistance system according to the invention with two electrical consumers is schematically shown in FIG. DETAILED DESCRIPTION

[0049] Figure 1A device is shown for supplying two electrical consumers with DC voltages U1 and U2. For this purpose, the device has a first DC voltage connection 1 and a second DC voltage connection 2, to which the DC voltages U1 and U2 are applied, as shown. For the voltage supply, the device has an energy supply unit 3, which is designed as an adjustable current source in the present embodiment. For this purpose, the energy supply unit 3 has a regulator 4, which regulates the output current of the energy supply unit 3 and thus controls the DC output voltage U0. The energy supply unit 3 is connected to the second DC voltage connection 2 without a transformer. Figure 1 In the embodiment of the present invention, a diode 8 is arranged between the energy supply unit 3 and the second DC voltage connection 2, the diode allowing a power flow in the direction of the second DC voltage connection as long as the DC output voltage U0 is greater than the forward voltage of the diode 8, and correspondingly, if the second DC voltage U2 should be greater than the DC output voltage U0, the diode correspondingly, in particular permanently, blocks a power flow in the direction of the energy supply unit. This situation occurs, for example, when energy is fed into the second DC voltage connection 2, for example, by an electric motor operating as a generator. Another situation in which diode blocking occurs occurs when no external energy is supplied to the energy supply unit 3 (U0=0) and a voltage U2 greater than zero is applied to the second DC voltage connection.

[0050] The first DC voltage U1 at the first DC voltage connection is different from the second DC voltage U2. For the use of the device in a MAS, it is common for the DC voltage U2 to be in the low voltage range, advantageously between 120 V and 600 V, in particular 300 V, and for the DC voltage U1 to be in the small voltage range, advantageously 12 V, 24 V or 48 V.

[0051] To convert DC voltage U2 into lower DC voltage U1, a converter 5 is provided between energy supply unit 3 and first DC voltage connection 1. Converter 5 is connected in parallel with second DC voltage connection 2 so that DC output voltage U0 is also used as input voltage for converter 5.

[0052] For buffering and energy storage, the device has two energy storage devices 6, 7. In the present embodiment, the first energy storage device 6 is designed as a battery storage device and is implemented as a secondary electrochemical element, for example. It is also conceivable that a rechargeable battery can be used as the first energy storage device 6. In the present embodiment, the second energy storage device 7 is implemented as a double-layer capacitor. In the embodiment shown, only the first and second energy storage devices are shown by way of example. However, modularly constructed energy storage devices are also conceivable, which are each composed of a plurality of energy storage devices of the same or different types.

[0053] Each energy storage device is supplied with energy by the energy supply unit 3. The energy storage device can store this energy and provide it to the corresponding electrical consumers. Here, the basic idea of ​​the present invention is that each energy storage device is designed and optimized to meet the needs of the corresponding electrical consumers. Therefore, each energy storage device should only be able to provide energy for its specific electrical consumers. To this end, it is necessary to ensure that no power flow occurs from one energy storage device to another energy storage device. In other words, round-trip charging / recharging (Umladen) should not be performed.

[0054] In the present embodiment, the power flow from the double-layer capacitor 7 to the battery storage 6 is blocked by a diode 8, which is located between the double-layer capacitor 7 and the interface of the conversion device 5. The power flow from the battery storage 6 to the double-layer capacitor 7 is blocked by the conversion device 5. For this purpose, the conversion device 5 is implemented as a unidirectional DC / DC converter. The unidirectionality is schematically shown here by a diode 9, which in this example follows a non-potentially isolated DC / DC converter 10. This arrangement only illustrates the functionality of the conversion device as a unidirectional DC / DC converter, wherein a power flow is only possible in the direction of the battery storage 6.

[0055] Figure 2 The use of the device for supplying voltage to two electrical consumers in a MAS is shown. The MAS is not shown further here. In this example, the conversion device 5 is implemented as a flyback converter. This flyback converter is an example of a potential-isolating, unidirectional DC / DC converter. As a result, a power flow from the battery storage 6 to the double-layer capacitor 7 is prevented. Charging of the double-layer capacitor 7 to the battery storage 6 is prevented by the diode 8.

[0056] In this exemplary embodiment, the first electrical consumer 11 is designed as a vehicle control unit. The vehicle control unit, among other things, controls the driving movement of the MAS. The control unit is supplied with a first DC voltage U1, which is typically 12 V, 24 V or 48 V. Other electrical consumers that can generally be referred to as vehicle electronics, for example safety sensors such as laser scanners and corresponding evaluation electronics, can also be supplied with this DC voltage U1.

[0057] For the driving movement, the MAS has a drive device 12, which can be implemented, for example, as a three-phase AC motor with an upstream three-phase inverter. The inverter converts the second DC voltage U2 into a three-phase AC voltage in a known manner, and the AC motor, such as a squirrel-cage rotor, is operated with this three-phase AC voltage. The drive device 12 can also have a plurality of motors, each of which can be operated with its own inverter. In addition, the inverter can also be implemented with feedback capability, so that the double-layer capacitor 7 can be charged when the drive motor is in generator mode. In addition to the drive device for traction of the MAS, other electrical consumers are also conceivable for the second DC voltage U2, such as a lifting device for receiving a load or a handling device for a moving object, such as a robot arm. These electrical consumers 5 are supplied with a second DC voltage U2 in the range of 120V to 600V.

[0058] The energy supply unit 3 for the vehicle can be implemented in different ways. For example, a simple charger with plug-in contacts can be implemented so that the MAS can be supplied with energy in a contact manner at a specific charging station. Likewise, it is also possible to implement a contact-type energy supply during the driving of the MAS by means of a power line, for example. As an alternative to this, a non-contact energy supply, such as an inductive energy supply, can also be implemented. This can take place here by coupled primary and secondary inductances. Here, it is also conceivable to supply power both at a fixed charging station and during the driving of the MAS, for example by means of a primary conductor laid in or on the hall floor. When there is an external energy supply, a DC output voltage U0 is provided by the energy supply unit 3. When there is no external energy supply, for example because the MAS is driving on a section without a power line or inductive power supply, the DC output voltage U0 is zero.

[0059] The energy storage device is primarily designed to supply the MAS with energy during operating phases when the MAS is not supplied with energy via the aforementioned external energy supply. This operating phase may be a journey between fixed charging stations or also a journey close to primary conductors or power lines.

[0060] Since recharging between the two energy stores is not possible, the energy stores can be designed and optimized for their specific tasks. The battery storage supplies the vehicle electronics, whose power consumption can be known in advance. The power consumption depends approximately on the operating time without external energy supply, and according to experience, a large safety factor is required to cope with unforeseen interruptions that lead to waiting times. The double-layer capacitor supplies the drive of the MAS, and the power consumption of the drive depends approximately on the driving distance without external energy supply, which is planned in advance, because the spatial layout of the charging infrastructure is known.

[0061] Figure 3A further embodiment of a MAS with two electrical consumers is shown. The same reference numerals denote the same components and in this respect reference is made to the above statements. In this example, the conversion device 5 comprises a potential-isolating DC / DC converter 13. The diode 9 again symbolically indicates that the conversion device 5 is a unidirectional DC / DC converter. The unidirectional DC / DC converter can prevent a power flow from the battery storage 6 to the double-layer capacitor 7.

[0062] and Figure 2 Compared to the embodiment without a diode, in this embodiment, there is no diode between the double-layer capacitor 7 and the conversion device 5, so that the voltage on the double-layer capacitor, i.e. the second DC voltage U2, corresponds to the DC output voltage U0 at any time. Therefore, for the embodiment without a diode, the voltage level U2 is discussed, and the voltage value therefore refers to the voltage applied to the double-layer capacitor and therefore also at the output end of the energy supply unit 3 in the embodiment without a diode. In the absence of external energy supply to the energy supply unit 3, when the double-layer capacitor still has a charge, the value of the DC output voltage U0 is therefore still greater than zero in this embodiment. It is even possible that U0 or U2 is increased despite the absence of external energy supply, for example when energy is fed in like a generator via the drive device 12. This is different from Figure 1 and Figure 2 In contrast to the exemplary embodiments of the present invention, the voltage values ​​U0 and U2 can be different due to the diode 8, so that the time profiles of the voltage levels U0 and U2 can therefore be different for these exemplary embodiments.

[0063] exist Figure 3 In the embodiment shown, the double-layer capacitor 7 is directly connected to the conversion device 5. The conversion device is also directly connected to the energy supply unit 3. Direct connection here means that there are no components arranged in the middle that could influence, i.e. control or prevent the power flow. In order to prevent charging from the double-layer capacitor 7 to the battery storage device 6 and back, especially permanently, i.e. at any point in time, in the present embodiment, a conversion control unit 14 is used, which monitors the voltage value of the voltage level U2 by means of a gradient evaluation. The second DC voltage U2 is therefore measured and its development over time is monitored. With the help of the gradient evaluation, the conversion control unit 14 checks whether the second DC voltage U2 increases (positive gradient). It is therefore checked whether energy is fed into the double-layer capacitor 7. This energy feed can come from the energy supply unit 3, or it can come from a temporary energy-generating electrical consumer, such as an electric motor operating as a generator. The above-mentioned gradient evaluation advantageously makes it possible to dispense with the need for, for example, a control circuit according to the embodiment of the invention. Figure 1 The double layer capacitor 7 and the diode between the conversion device 5 in the embodiment of the present invention can thus realize a direct connection of the two components. However, this direct connection is not absolutely necessary. Alternatively, it is also possible to arrange such a diode in the middle.

[0064] If the energy fed into the voltage level U2 is greater than the energy taken from it (positive gradient at voltage level U2), in particular from the minimum voltage value U 2,最小 Starting at a predefined charge level, the switching control 14 switches on the switching device 5 for charging the battery storage 6. This switching on can also be referred to as "activation". Minimum voltage value U 2,最小 Preferably, it is approximately below the usual target voltage value of the second DC voltage U2, in particular in the range of 80-95% of the target voltage value. For example, if a second DC voltage U2 = 300 V is to be aimed at as the target voltage in normal operation, then a minimum voltage value of 280 V can be selected, for example. This ensures that in the case of a positive gradient, the double-layer capacitor 7 is charged first before the battery storage device is also charged simultaneously.

[0065] If the energy fed into the voltage level U2 by the energy supply unit 3 is less than the energy obtained by the drive device 12 (non-positive gradient at the voltage level U2), the conversion device 5 is switched off by the conversion control unit 14. This switch-off can also be referred to as "deactivation". This switch-off process prevents the charging of the double-layer capacitor 7 to the battery storage 6.

[0066] Advantageously, the MAS has safety measures for protecting the energy storage devices. For this purpose, for example, the charging current, voltage and / or temperature of the energy storage devices are measured and evaluated in suitable evaluation devices. When certain critical current, voltage or temperature values ​​are reached, the energy storage devices are automatically deactivated in order to protect them from being destroyed.

[0067] List of reference numerals:

[0068] 1First DC voltage interface

[0069] 2 Second DC voltage interface

[0070] 3 Energy supply unit

[0071] 4 Regulator

[0072] 5Conversion equipment

[0073] 6First energy storage device

[0074] 7. Second energy storage device

[0075] 8 diodes

[0076] 9 diode

[0077] 10DC / DC Converter

[0078] 11. First power consumer

[0079] 12 Second power consumer

[0080] 13 Potentially isolated DC / DC converter

[0081] 14. Conversion control unit

[0082] U0 DC output voltage

[0083] U1 First DC voltage

[0084] U2 Second DC voltage

Claims

1. A method for operating an electric vehicle, the electric vehicle having: - an electric travel drive (12) for the travel movement of the vehicle, - a control device (11) for controlling the driving movement of the vehicle, a first energy storage device (6) for supplying a first DC voltage (U1) to the control device (11), - a second energy storage device (7) which can be charged and discharged faster than the first energy storage device (6), the second energy storage device being used to supply a second DC voltage (U2) to the travel drive (12), the second DC voltage being greater than the first DC voltage (U1), and - an energy supply unit (3), which provides a DC output voltage (U0), in, The first energy storage device (6) is connected to the energy supply unit via the conversion device (5). The second energy storage device (7) is connected to the energy supply unit (3). The conversion device (5) converts the DC output voltage (U0) into a first DC voltage (U1), wherein the first DC voltage (U1) is smaller than the DC output voltage (U0). It is characterized in that preventing a first power flow from the first energy storage device (6) to the second energy storage device (7), and A second power flow from the second energy storage device (7) to the first energy storage device (6) is prevented.

2. The method according to claim 1, characterized in that The electric vehicle is designed as an unmanned mobility assistance system, the first energy storage device (6) is designed as a rechargeable battery device, and the second energy storage device (7) is designed as a double-layer capacitor device, wherein the first power flow is blocked at any time, that is, at any point in time, and wherein the second power flow is blocked at any time, that is, at any point in time.

3. The method according to any one of the preceding claims, characterized in that An output current of the energy supply unit (3) has a value (I0) which is substantially constant over time, wherein the output current is controlled to this constant value (I0).

4. The method according to claim 1 or 2, characterized in that: Energy is supplied to the energy supply unit (3) in a contact-free or non-contact manner and / or energy is supplied to the energy supply unit (3) intermittently during driving.

5. The method according to claim 1 or 2, characterized in that: The first power flow is prevented by designing the conversion device (5) as a unidirectional DC / DC converter.

6. The method according to claim 1 or 2, characterized in that: The second power flow is prevented by a diode (8) arranged between the second energy storage device (7) and the conversion device (5).

7. The method according to claim 1 or 2, characterized in that: The second energy storage device (7) is directly connected to the energy supply unit (3) and / or directly connected to the conversion device (5), and the second power flow is prevented in the following manner, namely, the second DC voltage (U2) is monitored by means of gradient evaluation, wherein the conversion device (5) is activated when the gradient at the voltage level of the second DC voltage (U2) is positive, and the conversion device is deactivated when the gradient at the voltage level of the second DC voltage (U2) is non-positive.

8. The method according to claim 1 or 2, characterized in that: A first DC voltage (U1) for charging a first energy storage device (6) is changed.

9. The method according to claim 1 or 2, characterized in that: The second energy storage device (7) is designed to receive more current than can be provided by the energy supply unit (3).

10. The method according to claim 1, characterized in that The energy supply unit intermittently provides a DC output voltage (U0).

11. The method according to claim 5, characterized in that The conversion device (5) is designed as a potential-isolated DC / DC converter.

12. The method according to claim 7, characterized in that When the second DC voltage (U2) is greater than the minimum voltage value (U 2,最小 ), the conversion device (5) is activated.

13. The method according to claim 8, characterized in that A first DC voltage (U1) for charging a first energy storage device (6) is varied by means of a control device (11).

14. A device for supplying a first DC voltage (U1) to a first electrical consumer (11) of an electric vehicle and for supplying a second DC voltage (U2) to a second electrical consumer (12), the device comprising: a first energy storage device (6) which is designed as a rechargeable battery device, a second energy storage device (7) which is designed as a double-layer capacitor and / or which can be charged and discharged faster than the first energy storage device (6), and - an energy supply unit (3), capable of extracting a DC output voltage (U0) from the energy supply unit, in, A first DC voltage (U1) can be extracted from the first energy storage device (6), A second DC voltage (U2) can be extracted from the second energy storage device (7), and the second DC voltage (U2) is greater than the first DC voltage (U1). The first energy storage device (6) is connected to the energy supply unit via the conversion device (5). The second energy storage device (7) is connected to the energy supply unit (3). The conversion device (5) converts the DC output voltage (U0) into a first DC voltage (U1), wherein the first DC voltage (U1) is smaller than the DC output voltage (U0). It is characterized in that The device is configured to prevent a first power flow from the first energy storage device (6) to the second energy storage device (7) at any time, and to prevent a second power flow from the second energy storage device (7) to the first energy storage device (6) at any time.

15. The device according to claim 14, characterized in that The energy supply unit (3) is designed as an adjustable current source.

16. The device according to claim 14 or 15, characterized in that The first energy storage device (6) is arranged on the electric vehicle in a detachable manner, so that the first energy storage device (6) can be replaced.

17. The device according to claim 14 or 15, characterized in that Providing overvoltage protection and / or undervoltage protection and / or overcurrent protection on the first energy storage device (6) by means of current measurement and / or voltage measurement, and / or Providing overheating protection on the first energy storage device (6) by means of temperature measurement, and / or Providing overvoltage protection and / or overcurrent protection on the second energy storage device (7) by means of current measurement and / or voltage measurement, and / or By means of temperature measurement, overheating protection is provided at the second energy storage device (7).

18. The device according to claim 14, characterized in that Electric vehicles are driverless, mobile assistance systems for intralogistics applications.

19. An electric vehicle, the electric vehicle being used to carry out the method according to any one of claims 1 to 13, the electric vehicle having a device according to any one of claims 14 to 17, a first electrical consumer (11) and a second electrical consumer (12).

20. The electric vehicle according to claim 19, characterized in that The electric vehicle is a driverless mobility assistance system for intralogistics applications.

21. The electric vehicle according to claim 19, characterized in that: The first electrical consumer (11) is a control device for controlling the travel movement of the vehicle, and / or the second electrical consumer (12) is an electric travel drive device, a lifting device or a transport device for the travel movement of the vehicle.

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