METHOD FOR OPERATING AN ELECTRIC VEHICLE AND ELECTRIC VEHICLE

Abstract

In a method for operating an electric vehicle, including an electrical drive device for driving the vehicle, a control device for controlling the driving of the vehicle, a first energy storage device for supplying the control device with a first DC voltage, a second energy storage device for supplying the drive device with a second DC voltage, and an energy supply unit providing an output DC voltage, the first energy storage device is connected to the energy supply unit via a converter device, the second energy storage device is connected to the energy supply unit, the converter device converts the output DC voltage into the first DC voltage, 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.

Claims

1-15. (canceled)

16. A method for operating an electric vehicle, including an electrical drive device adapted to drive the vehicle, a control device for controlling driving movement of the vehicle, a first energy storage device adapted to supply the control device with a first DC voltage, a second energy storage device adapted to supply the drive device with a second DC voltage, and an energy supply unit adapted to provide an output DC voltage, the first energy storage device being connected via a converter device to the energy supply unit, the second energy storage device being connected to the energy supply unit, the converter device adapted to convert the output DC voltage into the first DC voltage, comprising: preventing a first power flow from the first energy storage device to the second energy storage device; and preventing a second power flow from the second energy storage device to the first energy storage device.

17. The method according to claim 16, wherein the driving movement of the vehicle includes traction of the vehicle, the second energy storage device is chargeable and dischargeable more rapidly than the first energy storage device, the second DC voltage is greater than the first DC voltage, the energy supply unit is adapted to periodically provide the output DC voltage, and the converter is adapted to convert the output DC voltage into the first DC voltage in response to the first DC voltage being smaller than the output DC voltage.

18. The method according to claim 16, wherein the electric vehicle is arranged as a driverless mobile assistance system, the first energy storage device includes a rechargeable battery storage device, the second energy storage device includes a double layer capacitor device, the first power flow is always prevented, and the second power flow is always prevented.

19. The method according to claim 16, wherein an output current of the energy supply unit has a value substantially constant over time.

20. The method according to claim 19, wherein the output current is regulated to the value substantially constant over time.

21. The method according to claim 16, wherein energy is supplied to the energy supply unit with contact or without contact.

22. The method according to claim 16, wherein energy is supplied periodically to the energy supply unit during travel.

23. The method according to claim 16, wherein therein the converter device including a unidirectional and/or electrically isolated DC/DC converter to prevent the first power flow.

24. The method according to claim 16, wherein the second power flow is prevented by a diode arranged between the second energy storage device and the converter device.

25. The method according to claim 16, wherein the second energy storage device is directly connected to the energy supply unit and/or directly connected to the converter device, the second power flow is prevented by monitoring the second DC voltage by a gradient evaluation, the converter device being activated in response to a positive gradient of a voltage level of the second DC voltage and/or in response to the second DC voltage being greater than a minimum voltage value, the converter device being deactivated in response to a non-positive gradient of the voltage level of the second DC voltage.

26. The method according to claim 16, wherein the first DC voltage for charging the first energy storage device is varied.

27. The method according to claim 16, wherein the first DC voltage for charging the first energy storage device is varied by the control device.

28. The method according to claim 16, wherein the second energy storage device is adapted to receive more current than can be provided by the energy supply unit.

29. A device for supplying a first load of an electric vehicle with a first DC voltage and for supplying a second load with a second DC voltage, comprising: a first energy storage device adapted to supply the first DC voltage; a second energy storage device adapted to supply the second DC voltage; an energy supply unit adapted to supply an output DC voltage, the first energy storage device being connected via a converter device to the energy supply unit, the second energy storage device being connected to the energy supply unit; wherein the converter device is adapted to convert the output DC voltage into the first DC voltage; wherein the device is adapted to prevent a first 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.

30. The device according to claim 29, wherein the electric vehicle is arranged as a driverless mobile assistance system of an intralogistics application, the first energy storage device includes a rechargeable battery storage device, the second energy storage device is arranged as a double layer capacitor device and/or is chargeable and dischargeable more rapidly than the first energy storage device, the energy supply unit is adapted to periodically supply the output DC voltage, the second DC voltage is greater than the first DC voltage, the converter device is adapted to convert the output DC voltage into the first DC voltage in response to the first DC voltage being smaller than the output DC voltage, and the device is adapted to always prevent the first power flow from the first energy storage device to the second energy storage device and to always prevent the second power flow from the second energy storage device to the first energy storage device.

31. The device according to claim 29, wherein the energy supply unit includes a controllable current source.

32. The device according to claim 29, wherein the first energy storage device is arranged removably and replaceable on the electric vehicle.

33. The device according to claim 29, wherein the first energy storage device includes an overvoltage protection, an undervoltage protection, and/or an overcurrent protection by a current measurement and/or a voltage measurement.

34. The device according to claim 29, wherein the first energy storage device includes an overtemperature protection by a temperature measurement.

35. The device according to claim 29, wherein the second energy storage device includes an overvoltage protection and/or an overcurrent protection by a current measurement and/or a voltage measurement.

36. The device according to claim 29, wherein the second energy storage device includes an overtemperature protection by a temperature measurement.

37. An electric vehicle, comprising: a device adapted to supply a first load of an electric vehicle with a first DC voltage and to supply a second load with a second DC voltage, including: a first energy storage device adapted to supply the first DC voltage; a second energy storage device adapted to supply the second DC voltage; an energy supply unit adapted to supply an output DC voltage, the first energy storage device being connected via a converter device to the energy supply unit, the second energy storage device being connected to the energy supply unit; wherein the converter device is adapted to convert the output DC voltage into the first DC voltage; wherein the device is adapted to prevent a first 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; an electrical drive device adapted to drive the vehicle; and a control device adapted to control driving movement of the vehicle; wherein the first energy storage device is adapted to supply the control device with the first DC voltage, and the second energy storage device is adapted to supply the drive device with the second DC voltage; and wherein the electric vehicle is adapted to perform a method including: preventing the first power flow from the first energy storage device to the second energy storage device; and preventing the second power flow from the second energy storage device to the first energy storage device.

38. The electric vehicle according to claim 37, wherein the electric vehicle is arranged a driverless mobile assistance system of an intralogistics application.

39. The electric vehicle according to claim 37, wherein the first load includes the control device and/or the second load includes an electrical drive device for the driving movement of the vehicle, a lifting device, or a handling device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 schematically illustrates a device according to an example embodiment of the present invention for the voltage supply of two loads of a mobile assistance system. The mobile assistance system is also referred to as MAS below.

[0047] FIG. 2 schematically illustrates a mobile assistance system with two loads.

[0048] FIG. 3 schematically illustrates a mobile assistance system with two loads.

DETAILED DESCRIPTION

[0049] FIG. 1 schematically illustrates a device for the voltage supply of two loads with the DC voltages U.sub.1 and U.sub.2. For this purpose, the device includes a first DC voltage connection 1 and a second DC voltage connection 2, on which the DC voltages U.sub.1 and U.sub.2 are applied. For the energy supply, the device includes an energy supply unit 3 which, in this example embodiment, is arranged as a controllable current source. For this purpose, the energy supply unit 3 includes a controller 4 which regulates the output current of the energy supply unit 3 and thus controls the output DC voltage U.sub.0. The energy supply unit 3 is connected without voltage converter to the second DC voltage connection 2. In the example embodiment illustrated in FIG. 1, between the energy supply unit 3 and the second DC voltage connection 2, a diode 8 is arranged, which allows a power flow in the direction of the second DC voltage connection, provided that the output DC voltage U.sub.0 is greater than the forward voltage of the diode 8, and accordingly prevents, e.g., permanently, a power flow in the direction of the energy supply unit should the second DC voltage U2 be greater than the output DC voltage U.sub.0. This would be the case, for example, if, on the second DC voltage connection 2, energy is fed in, for example, by an electric motor operated as generator. Another situation in which the diode blocks is the case in which no external energy is supplied to the energy supply unit 3 (U.sub.0=0) and a voltage U.sub.2 greater than zero is applied on the second DC voltage connection.

[0050] The first DC voltage U.sub.1 on the first DC voltage connection differs from the second DC voltage U.sub.2. For the application of the device in a MAS, DC voltages U.sub.2 in the range of low voltages, e.g., in the range between 120 V and 600 V, e.g., 300 V, and DC voltages U.sub.1 in the range of low voltages, e.g., 12 V, 24 V or 48 V, may be utilized.

[0051] In order to convert the DC voltage U.sub.2 into the lower DC voltage U.sub.1, a converter device 5 is present between the energy supply unit 3 and the first DC voltage connection 1. The converter device 5 is parallel connected to the second DC voltage connection 2, so that the output DC voltage U.sub.0 as well is used as input voltage for the converter device 5.

[0052] For buffering and energy storage, the device includes two energy storages 6, 7. In this example embodiment, the first energy storage 6 is configured as battery storage and, for example, is implemented as a secondary electrochemical element. Likewise, a rechargeable battery is possible as energy storage 6. In this example embodiment, the second energy storage 7 is implemented as double layer capacitor. In the illustrated example embodiment, for example, in each case only a first energy storage and a second energy storage are shown. However, energy storage devices of modular configuration are also possible, each including multiple identical or different energy storages.

[0053] Energy is supplied to each energy storage by the energy supply unit 3. The energy storage can store this energy and make it available to a corresponding load. Each energy storage is in each case configured and optimized for the requirements of the corresponding load. The respective energy storage should therefore be able to deliver energy only to its particular load. For this purpose, it is provided that a power flow from one energy storage to another cannot occur. Thus, no transfer should occur.

[0054] In the present example embodiment, a power flow from the double layer capacitor 7 to the battery storage 6 is prevented by the diode 8 located between the double layer capacitor 7 and the connection of the converter device 5. A power flow from the battery storage 6 to the double layer capacitor 7 is prevented by the converter device 5. For this purpose, the converter device 5 is implemented as a unidirectional DC/DC converter. The unidirectionality is schematically illustrated by a diode 9 which, in this example, follows a nonelectrically isolated DC/DC converter 10. This arrangement is intended merely to illustrate the functionality of the converter device as unidirectional DC/DC converter, in which a power flow is possible only in direction of the battery storage 6.

[0055] FIG. 2 illustrates an application of the device for the voltage supply of two loads in a MAS. In this example, the converter device 5 is implemented as a flyback converter. This is an example of an electrically isolated unidirectional DC/DC converter. Thus, a power flow from the battery storage 6 to the double layer capacitor 7 is prevented. A transfer from the double layer capacitor 7 to the battery storage 6 is prevented by the diode 8.

[0056] In this example embodiment, the first load 11 is configured as vehicle control. The vehicle control controls the driving movement of the MAS, for example. The control is supplied with the first DC voltage U.sub.1 which is typically 12 V, 24 V, or 48 V. Other loads as well, which generally can be referred to as vehicle electronics, can be supplied with this DC voltage U.sub.1, for example, security sensors such as laser scanners and corresponding evaluation electronics.

[0057] For the driving movement, the MAS has a drive device 12 which can be configured, for example, as 3-phase motor with upstream 3-phase inverter. The inverter converts the second DC voltage U.sub.2 into a three-phase AC voltage with which the 3-phase motor, for example, a cage rotor, is operated. The drive device 12 can also include multiple motors which can each be operated by an individual inverter. In addition, the inverter can also be implemented as energy recovering, so that, when the drive motors are operated as generator, a charging of the double layer capacitor 7 is possible. In addition to drive devices for the traction of the MAS, other loads for the second DC voltage U.sub.2 are also possible, such as, for example, lifting devices for picking up a load or handling devices for moving an object, for example, a robot arm. These loads 5 are supplied with the second DC voltage U.sub.2 in the range from 120 V to 600 V.

[0058] The energy supply unit 3 for the vehicle can be implemented differently. For example, a simple charging apparatus with plug contact can be implemented, so that the MAS can be supplied with energy with contact at certain charging stations. Likewise, an energy supply with contact during travel of the MAS can be implemented, for example, by conductor lines. Alternatively, an energy supply without contact can be implemented, for example, an inductive energy supply. This can occur by coupled primary and secondary inductances. Both supplying at a stationary charging station and also supplying during the travel of the MAS are possible, for example, by primary conductors installed in or on the hall floor. When an external energy supply is present, the output DC voltage U.sub.0 is provided by the energy supply unit 3. If no external energy supply is present, for example, because the MAS is travelling over a section without conductor lines or inductive supply, the output DC voltage U.sub.0 is consequently zero.

[0059] The energy storages are configured primarily in order to supply the MAS with energy during operating phases in which the MAS has no external energy supply as previously described. This can be trips between stationary charging stations or trips which are remote from the primary conductor or conductor lines.

[0060] Since no transfer between the two energy storages is possible, the energy storages can each be configured and optimized for their particular task. The battery storage supplies the vehicle electronics, the consumption of which can be determined in advance. The consumption depends approximately on the duration of operation without external energy supply and, based on experience, requires greater safety margins for unforeseen disturbances which lead to waiting times. The double layer capacitor supplies the drives of the MAS, and their consumption depends approximately on the driving route without external energy supply, which can be planned well in advance, since the spatial arrangement of the charging infrastructure is known.

[0061] FIG. 3 schematically illustrates a MAS with two loads. Identical reference numerals denote identical components, and reference is made to the above explanations for such components. In this example, the converter device 5 includes an electrically isolated DC/DC converter 13. The diode 9 is again intended to symbolize that the converter device 5 is a unidirectional DC/DC converter. By this unidirectional DC/DC converter, a power flow from the battery storage 6 to the double layer capacitor 7 is prevented.

[0062] In contrast to the example embodiment illustrated in FIG. 2, in this example embodiment, there is no diode between the double layer capacitor 7 and the converter device 5, and for this reason, at any point in time, the voltage on the double layer capacitor, e.g., the second DC voltage U.sub.2, corresponds to the output DC voltage U.sub.0. Therefore, for the example embodiment without a diode, one speaks of a voltage level U.sub.2, meaning the voltage value of the voltage which is applied in the example embodiment without a diode on the double layer capacitor and consequently also on the output of the energy supply unit 3. In the case of absence of external energy supply of the energy supply unit 3, in this example embodiment, the value of the output DC voltage U.sub.0 is thus nevertheless greater than zero if the double layer capacitor still has a charge. It is even possible that U.sub.0 or U.sub.2 increases, even though no external energy supply is present, for example, if energy is fed in via the drive device 12 operated as generator. This is a difference from the example embodiments illustrated in FIGS. 1 and 2, in which the voltage values U.sub.0 and U.sub.2 can be different due to the diode 8, and the voltage levels U.sub.0 and U.sub.2 can thus differ in the time course for these example embodiments.

[0063] In the example embodiment illustrated in FIG. 3, the double layer capacitor 7 is directly connected to the converter device 5. It is also directly connected to the energy supply unit 3. Directly connected here means that no components which can influence, e.g., control or prevent, a power flow are arranged in between. In the present example embodiment, in order to prevent a transfer from the double layer capacitor 7 to the battery storage 6, e.g., permanently, e.g., at any point in time, a converter control 14 is used, which monitors the voltage value of the voltage level U.sub.2 by a gradient evaluation. Thus, the second DC voltage U.sub.2 is measured and its measurement over time is monitored. By the gradient evaluation, the converter control 14 checks to determine whether second DC voltage U.sub.2 increases (positive gradient). Thus, a check is conducted to determine whether energy is fed into the double layer capacitor 7. This feeding in of energy can come from the energy supply unit 3 or from a load which temporarily generates energy, for example, an electric motor operated as generator. Due to the mentioned gradient evaluation, a diode between double layer capacitor 7 and converter device 5, as in the example embodiment illustrated in FIG. 1, can be dispensed with, e.g., a direct connection of the two components can be implemented. However, this direct connection is not absolutely necessary. Alternatively, such a diode could also be arranged in between.

[0064] To the extent that more energy is fed into the voltage level U.sub.2 than is drawn therefrom (positive gradient of voltage level U.sub.2), the converter control 14, e.g., starting at a charge level of the double layer capacitor 7, predefined by a minimum voltage value U.sub.2,min, switches the converter device 5 on in order to charge the battery storage 6. This switching on can also be referred to as “activation.” The minimum voltage value U.sub.2,min is, e.g., just below the usual target voltage value of the second DC voltage U.sub.2, e.g., in the range of 80-95% of the target voltage value. If, for example, in normal operation, the goal is a second DC voltage U.sub.2=300 V as target voltage, then, for example, a minimum voltage value of 280 V can be selected. Thereby, it is provided that, in the case of a positive gradient, first the double layer capacitor 7 is charged before the battery storage is also charged in parallel thereto.

[0065] If less energy is fed into the voltage level U.sub.2 by the energy supply unit 3 than is drawn by the drive device 12 (no positive gradient of voltage level U.sub.2), then the converter device 5 is switched off by the converter control 14. This switching off can also be referred to as “deactivation.” This switching off process prevents a transfer from the double layer capacitor 7 to the battery storage 6.

[0066] For example, the MAS has safety measures for the protection of the energy storages. For this purpose, for example, charging current, voltage, and/or temperature of the energy storages are measured and evaluated in an appropriate evaluation device. When certain critical current, voltage or temperature values are reached, the energy storages are automatically deactivated in order to protect them from destruction.

LIST OF REFERENCE CHARACTERS

[0067] 1 First DC voltage connection [0068] 2 Second DC voltage connection [0069] 3 Energy supply unit [0070] 4 Controller [0071] 5 Converter device [0072] 6 First energy storage device [0073] 7 Second energy storage device [0074] 8 Diode [0075] 9 9 Diode [0076] 10 DC/DC converter [0077] 11 First load [0078] 12 Second load [0079] 13 Electrically isolated DC/DC converter [0080] 14 Converter control [0081] U.sub.0 Output DC voltage [0082] U.sub.1 First DC voltage [0083] U.sub.2 Second DC voltage