Electrical System For A Vehicle Which Can Be Electrically Driven

Abstract

An electrical system for a vehicle which can be electrically driven includes a high-voltage DC system and a low-voltage DC system. A DC/DC converter is, or can be, electrically connected to the high-voltage DC system at one end and to the low-voltage DC system at the other end. An AC line passage is, or can be, electrically connected to a first DC/AC converter. The first DC/AC converter is, or can be, electrically connected to the high-voltage DC system at one end and to an AC drive device of the vehicle by way of the AC line passage at the other end. There is also included a DC energy source, in particular a fuel cell device for example. A second DC/AC converter is, or can be, electrically connected to the DC energy source at one end and to the AC line passage at the other end.

Claims

1-8. (canceled)

9. An electrical system for a vehicle which can be electrically driven, the electrical system comprising: a high-voltage DC network with a high-voltage DC energy storage device; a low-voltage DC network with a low-voltage DC energy storage device; a DC/DC converter having a first side electrically connected or connectable to said high-voltage DC network and a second side connected or connectable to said low-voltage DC network in order to permit the transmission of electrical energy from said high-voltage DC network to said low-voltage DC network and/or vice versa; a first DC/AC converter and an AC line passage electrically connected or connectable to said first DC/AC converter, said first DC/AC converter having a first side electrically connected or connectable to said high-voltage DC network, and a second side connected, via said AC line passage, to an AC drive device of the vehicle, for permitting a transmission of electrical energy between said high-voltage DC network and said AC drive device via said first DC/AC converter and via said AC line passage; a DC energy source for generating electrical energy for supplying the electrical system; a second DC/AC converter having a first side electrically connected or connectable to said DC energy source and a second side connected or connectable to said AC line passage, in order to permit a transmission of electrical energy generated by said DC energy source via said second DC/AC converter and further via said first DC/AC converter to said high-voltage DC network and/or to permit a transmission of electrical energy generated by said DC energy source via said second DC/AC converter to the AC drive device of the vehicle.

10. The electrical system according to claim 9, wherein said high-voltage DC network is rated for a nominal service voltage of no less than 300 V.

11. The electrical system according to claim 9, wherein said low-voltage DC network is rated for a nominal service voltage not exceeding 120 V.

12. The electrical system according to claim 11, wherein said low-voltage DC network is rated for a nominal service voltage not exceeding 24 V.

13. The electrical system according to claim 9, wherein said DC energy source comprises a fuel cell device.

14. The electrical system according to claim 9, further comprising a first controllable switching device for the controllable connection and disconnection between the AC drive device and said AC line passage.

15. The electrical system according to claim 14, further comprising a second controllable switching device for the controllable connection and disconnection between said DC energy source and said AC line passage.

16. The electrical system according to claim 9, further comprising a charger connection device connected or connectable to said AC line passage.

17. A vehicle which can be electrically driven, comprising an electrical system according to claim 9.

Description

[0040] The invention is further described hereinafter on the basis of exemplary embodiments, with reference to the attached drawings. Herein:

[0041] FIG. 1 shows a block diagram for the illustration of the electrical system of a fuel cell vehicle of the conventional type, and

[0042] FIG. 2 shows a block diagram of the electrical system of a fuel cell vehicle according to an exemplary embodiment of the invention.

[0043] For the purposes of the understanding of the invention, FIG. 1 represents the key components of an electrical system 10 of conventional design for a vehicle which can be electrically driven.

[0044] The system 10 comprises a high-voltage DC network 12 with a high-voltage DC energy store 14. In the exemplary embodiment represented, the high-voltage DC network 12 is formed of a two-pole conductor arrangement with a nominal service voltage of e.g. 400 V. In the example represented, the high-voltage DC energy store 14 comprises a lithium-ion accumulator.

[0045] The system 10 moreover comprises a low-voltage DC network 16 (in this case with a nominal voltage of e.g. 12 V), with a low-voltage DC energy store 18 (in this case e.g. a lead-acid accumulator) connected thereto. The function of the network 16 is the supply of consumers 21.

[0046] In order to permit the exchange of electrical energy between the two on-board networks 12, 16 as required, these networks 12, 16 are electrically interconnected by means of a bi-directional DC/DC converter 20.

[0047] The high-voltage DC network 12 is moreover electrically connected to the DC side of a DC/AC converter 22, the AC side of which, via a three-pole AC line passage 24 (three-phase AC line), is electrically connected to an electrical AC drive device 26 (in this case e.g. a three-phase AC motor).

[0048] For the electrical propulsion of the vehicle, the DC/AC converter 22, in a conventional manner, is controlled by an (unrepresented) control device to operate as an inverter, for the inversion of the network-side DC voltage and the output-side delivery of a corresponding AC voltage to the AC drive device 26 via the AC line passage 24.

[0049] For operation in recovery mode, e.g. for a recovery of the braking energy of the vehicle, the DC/AC converter 22 is operated in the reverse direction, for the rectification of an AC voltage induced in the AC drive device, which AC voltage is then employed for the recharging of the high-voltage DC energy store.

[0050] The system 10 moreover comprises a DC energy source 28, in this case in the form of a fuel cell device, for the generation of electrical energy for the supply of the system 10. The DC energy source 28 is electrically connected to the high-voltage DC network 12 via a further DC/DC converter 30. By means of the (uni-directionally configured) DC/DC converter 30, energy generated by the DC energy source can thus be transmitted to the high-voltage DC network 12.

[0051] Finally, the system 10 comprises a charger connection device 32, in this case e.g. a two-pole socket-contact device, which is electrically connected to the high-voltage DC network 12 via an AC/DC converter 34, in order to permit a recharging of the high-voltage DC energy store 14 from an external AC grid system, when the vehicle is parked.

[0052] The known design illustrated in FIG. 1 has a comparatively high weight and a high spatial requirement.

[0053] Hereinafter, with reference to FIG. 2, an electrical system of simplified design is described for a vehicle which can be electrically driven, which nevertheless delivers the same functionalities as the system 10 represented in FIG. 1.

[0054] In the following description of an exemplary embodiment according to the invention, components of equivalent function are identified by the same reference numbers, but with the addition of a lower case “a” in each case, for the purposes of the distinction of this form of embodiment. Essentially, only differences from the exemplary embodiment already described are addressed and, to this end, specific reference is moreover included to this aforementioned exemplary embodiment.

[0055] FIG. 2 represents the components of an electrical system 10a for a fuel cell vehicle.

[0056] The system 10a comprises a high-voltage DC network 12a with a high-voltage DC energy store 14a. In the exemplary embodiment represented, the high-voltage DC network 12a is formed of a two-pole conductor arrangement with a nominal service voltage of e.g. 400 V. The high-voltage DC energy store 14a comprises a lithium-ion accumulator.

[0057] The system 10a moreover comprises a low-voltage DC network 16a (with a nominal voltage of e.g. 12 V), with a low-voltage DC energy store 18a (in this case e.g. a lead-acid accumulator) connected thereto.

[0058] In order to permit the exchange of electrical energy between the two on-board networks 12a, 16a as required, these networks 12a, 16a are electrically interconnected by means of a bi-directionally configured DC/DC converter 20a.

[0059] The high-voltage DC network 12a is moreover connected via a first DC/AC converter 22a to an AC line passage 24a which, in the example represented, is configured as a three-pole three-phase AC line passage.

[0060] The AC line passage 24a is routed to an electrical AC drive device 26a (in this case e.g. a three-phase AC motor).

[0061] The electrical propulsion of the vehicle, and an operation in recovery mode, can thus be executed in the manner described above for the known system 10 with reference to FIG. 1.

[0062] By distinction from the known system 10, the system according to the invention 10a has the following specific features:

[0063] In order to make the energy generated by a DC energy source 28a (in this case e.g. a fuel cell device, wherein alternatively e.g. a combustion engine in combination with an electric generator is also possible) available for use by the system 10a, a second DC/AC converter 40a is provided, which is electrically connected on one side (the DC side) to the DC energy source 28a, and on the other side (the AC side) to the AC line passage 24a.

[0064] It is thus possible to transmit electrical energy generated by the DC energy source 28a via the second DC/AC converter 40a, and moreover via the first DC/AC converter 22a to the high-voltage DC network 12a. Alternatively or additionally, it is possible for such electrical energy generated by the DC energy source 28a to be transmitted via the second DC/AC converter 40a and the AC line passage 24a to the AC drive device 26a.

[0065] A further specific feature of the system 10a is provided, in that a first controllable switching device S1 for the controllable connection of the AC drive device 26a to the AC line passage 24a and the disconnection of the AC drive device 26a from the AC line passage 24a, and a second controllable switching device S2 for the controllable connection of the DC energy source 28a to the AC line passage 24a and the disconnection of the DC energy source 28a from the AC line passage 24a, are provided.

[0066] A further specific feature of the system 10a is provided, in that a charger connection device 32a is connected to the AC line passage 24a.

[0067] The electrical system 10a according to the invention constitutes an optimization of the entire electrical architecture of the vehicle. Specifically, this involves optimization by a reduction of components, with no resulting impairment of functionality. Specifically, by the electrical connection of the two DC/AC converters 22a, 40a, the functionality of the additional DC/DC converter provided according to the prior art can be achieved. This permits the omission of the DC/DC converter for the connection of the DC energy source 28a (“range extender”) and the electrical energy store. During driving, the high-voltage DC energy store 14a and the DC energy source 28a (fuel cells) can simultaneously be employed, in a highly efficient manner, as an energy source for vehicle propulsion. In the system 10a according to the invention, a dedicated AC/DC converter for the provision of an external recharging facility can also be omitted.

[0068] The vehicle states or operating modes which are achievable e.g. by means of a program-controlled electronic control device, by the corresponding control of the various converters and switching devices, are further summarized in the following table.

TABLE-US-00001 First Second DC/AC DC/AC Switching Switching Vehicle state: converter: converter: device S1: device S2: Driving DC/AC DC/AC closed open or (propulsion) conversion conversion closed Braking AC/DC not closed open (recovery) conversion employed Charging from AC/DC not open open an external conversion employed grid system Charging from DC/AC AC/DC closed closed DC energy conversion conversion or source (e.g. open fuel cells)

[0069] In the “driving (propulsion)” state, with the switching device S2 closed, energy from the DC energy source can be employed.

[0070] In the “charging from DC energy source” state, with the switching device S1 closed, energy from the DC energy source can simultaneously be employed for the propulsion of the vehicle.