DE102015016932A1 - Electrical system for an electrically driven motor vehicle - Google Patents

Abstract

The invention relates to an electrical installation (46) for an electrically driven motor vehicle, having an inverter (32) to which a rotating electrical machine (24) for driving the motor vehicle can be connected, having an electrical energy storage converter (30) designed for bidirectional energy conversion. for connecting an electrical energy store (18) and having a DC intermediate circuit (28) having a DC link inductance (44) for electrically coupling the inverter (32) to the energy store converter (30), wherein the electrical energy store converter (30) is designed, the DC link inductance (44 ) to use for converting the electrical energy, wherein the electrical system (46) to the DC intermediate circuit (28) connected decoupling unit (26, 36) for connecting an electrical energy source (12), wherein the decoupling unit (26, 36) is formed , the electrical energy source (12) el Electrically decouple from the DC link (28) when the power source (12) the DC intermediate circuit (28) does not supply electrical energy.

Description

The present invention relates to an electrical system for an electrically driven motor vehicle, comprising an inverter, to which a rotating electrical machine for driving the motor vehicle can be connected, with an electrical energy storage converter designed for bidirectional energy conversion for connecting an electrical energy store and having a DC link inductance DC link for electrically coupling the inverter to the energy storage transducer, wherein the electrical energy storage converter is adapted to use the DC link inductance for converting the electrical energy. In addition, the invention relates to a method for operating an electrical system of an electrically driven motor vehicle, wherein the motor vehicle is driven by means of a connected to an inverter rotating electrical machine, for which purpose the inverter via a DC link having a direct current intermediate circuit electrically coupled to an electrical energy store wherein coupling takes place by means of an electrical energy storage converter designed for bidirectional energy conversion, which uses the DC link inductance to convert the electrical energy.

Electrical installations for electrically driven motor vehicles and methods for their operation are basically known from the prior art, for example from US Pat US 6,321,145 , This discloses an electrical system for an electrically driven motor vehicle, in which a fuel cell is connected via a boost converter to a Leistungsakkumulator, which in turn is connected via a DC voltage intermediate circuit to an inverter. The inverter provides a three-phase AC mains for connection to a three-phase AC electrical machine.

Generic electrical systems and methods for their operation are also known from the DE 10 2013 014 388 A1 , From this document it is known to form electrical systems with a DC intermediate circuit instead of a DC voltage intermediate circuit. Although the teaching of this document has proven itself, it proves difficult when using a DC intermediate circuit to connect a fuel cell and at the same time provide a possibility for recuperation by means of the electrical system. Therefore, the reveals DE 10 2013 014 388 A1 Also, only a motor vehicle, which is driven by means of the electrical machine designed for a three-phase network, wherein the electric machine is connected via an inverter to a DC intermediate circuit, which in turn is connected via an electrical energy converter only to an accumulator. The DC intermediate circuit has a DC link, by means of which the current flowing through the DC intermediate circuit is predeterminably adjustable. In order for the inverter to be reliably operated on the DC link, the inverter constructed as a three-phase inverter has back-blocking bipolar transistors with insulated gate (IGBT) as semiconductor switching elements. In this respect, this drive concept deviates from widely used in the prior art drive concepts that use a DC voltage intermediate circuit, as for example by the US 6,321,145 is disclosed.

The problem with the use of DC intermediate circuits is the parallel connection of further units, wherein at the same time it must be ensured that the current flow can be reliably ensured in a predeterminable manner. Unlike a DC link where the electrical current is a variable magnitude, in a dual mode DC link the voltage is the variable magnitude. For this reason is at the DE 10 2013 014 388 A1 merely intended to couple two components by means of the DC intermediate circuit, namely the accumulator and the inverter. It would be desirable to connect to the DC intermediate circuit and other components in a simple manner and at the same time to enable reliable operation can.

It is therefore an object of the invention to improve a generic electrical system with a DC intermediate circuit and a method for their operation in terms of flexibility and usability.

As a solution, an electrical system according to claim 1 is proposed with the invention. With the further independent claim 6, a corresponding method is proposed.

Further embodiments and advantages will become apparent from the features of the dependent claims.

With the invention is proposed in a generic electrical system in particular that the electrical system has a DC link connected to the decoupling unit for connecting an electrical energy source, wherein the decoupler is designed to decouple the electrical energy source electrically from the DC link when the power source the DC intermediate circuit no supplying electrical energy.

In terms of the method, in a generic method, in particular, it is proposed that an electrical energy source connected to the DC intermediate circuit via a decoupling unit be electrically decoupled from the DC intermediate circuit by means of the decoupling unit when the electrical energy source does not supply electrical energy to the DC intermediate circuit.

The decoupling unit serves to couple the electrical energy source with the DC intermediate circuit in a predetermined manner. In addition, a unidirectional energy flow is preferably realized by means of the decoupling unit, that is, only electrical energy is supplied from the electrical energy source to the DC intermediate circuit. In the opposite direction no energy flow takes place. In this respect, the electrical energy source is protected by the decoupling of an undesirable energy supply from the DC link, as they might otherwise occur, for example, in recuperation.

The decoupling unit can have, for example, a diode as a decoupling element, in particular a semiconductor diode or the like. However, it is also possible to provide a reverse-blocking semiconductor switching element, by means of which the current flow is possible only in the switched-on state of the semiconductor switching element. Any inverse diodes are deactivated or absent in such a semiconductor switching element. The decoupling element can therefore be an electronic component, which ensures that a power flow is only possible from the electrical energy source into the DC intermediate circuit. Such a component may, for example, also comprise one or more semiconductor switching elements, diodes, combination circuits thereof and / or the like.

The invention makes use of the insight that, in the case of a DC intermediate circuit, the variable variable is not the electric current as in the case of a DC intermediate circuit, but rather the electrical voltage. As a result, the energy source - unlike a DC voltage intermediate circuit - can not be connected directly to the DC link, in particular also because the electrical voltage at the DC link can become negative, for example in recuperation mode. Since the energy source is often not suitable for receiving electrical energy, additional measures are required to ensure that the electrical energy source can not be supplied with electrical power itself. This purpose is served by the decoupling unit. The decoupling unit ensures that an energy flow can only take place from the energy source in the direction of the DC intermediate circuit. An energy flow from the DC intermediate circuit in the direction of the energy source, however, is prevented by the decoupling unit. Energy sources which come into consideration as electrical energy sources in the context of the invention are in particular fuel cells, but also non-rechargeable batteries, wind generators, solar cells and / or the like. The electrical energy source is thus preferably an electrical device that can only emit electrical energy. In contrast, the electrical energy storage device is a device that can both emit electrical energy and absorb electrical energy. Such electrical energy storage devices are, for example, accumulators, capacitors, in particular supercaps, combinations thereof or the like.

An inverter is a form of an energy converter, by means of which electrical energy, which is supplied on the DC side or DC side, into electrical energy of an AC voltage, in particular a single-phase or a three-phase AC voltage, or an AC, in particular a single-phase or a three-phase AC, are converted can. The energy can be changed bidirectionally. Such inverters are nowadays usually designed as clocked electronic energy converters and, for this purpose, have at least one half-bridge module for a respective alternating voltage or alternating current phase, by means of which an electrical energy provided by means of an intermediate circuit can be converted into an alternating electrical voltage or an alternating current and vice versa. For this purpose, the half-bridge module has two series-connected semiconductor switches which are operated by a clock in the clock mode, so that in the desired manner, the AC voltage or the AC at a center terminal of the half-bridge module, which is formed by an electrical connection point of the two semiconductor switches of the half-bridge module, provided. Such a circuit topology is also called a half-bridge circuit. If only a single half-bridge module is present, the inverter is therefore designed for a so-called single-phase operation.

In order to be able to implement larger powers, it can be provided in such a single-phase inverter that two half-bridge modules are provided in parallel, which are operated in a complementary manner, whereby the AC voltage or the alternating current is provided between the two center terminals. As a result, the height of the generated AC voltage can be doubled in the reason. Such a circuit topology is also called a full-bridge circuit.

If two or more alternating voltage or alternating current phases are required, a half-bridge module or a full-bridge module are respectively provided for each of the alternating voltage or alternating-current phase.

Semiconductor switches in the sense of this disclosure are preferably controllable electronic switching elements, for example a transistor, a thyristor, combination circuits thereof, in particular a metal oxide semiconductor field effect transistor (MOSFET), an isolated gate bipolar transistor (IGBT) or the like.

For operation on a DC intermediate circuit, the semiconductor switch is preferably reverse-blocking, that is to say that in the case of inverse voltage application of a switching path of the semiconductor switch to the switching path, a current flow in the switched-off state is prevented. In particular, it is provided that any system-related inverse diodes are deactivated by circuitry. For example, this can be achieved by a diode connected in series to the switching path of the respective semiconductor switch.

The switching operation of the semiconductor switch means that a very low electrical resistance is provided in an on state between the terminals forming the switching path of the semiconductor switch, so that a high current flow at very low residual voltage is possible. When switched off, the switching path of the semiconductor switch is high impedance, that is, it provides a high electrical resistance, so that there is substantially no or only a very low, in particular negligible current flow even at high voltage applied to the switching path. This differs from a linear operation, which is usually not used in clocked energy converters.

The rotating electrical machine is usually designed for AC voltage or AC machine, which may have one, two, three or even more electrical phases depending on the design. Accordingly, the inverter is designed to operate the rotating electrical machine can. Such rotating electrical machines may be, for example, a synchronous machine, an asynchronous machine or the like. In addition, of course, there is also the possibility to use a DC or DC machine. In this case, the inverter is replaced by a bidirectional DC / DC converter. However, a rotating electrical machine for alternating voltage or alternating current is preferably used.

The inverter is coupled via the DC link with the electrical energy storage. The DC intermediate circuit has for this purpose the DC link inductance, which maintains the current flow during normal operation. The DC link inductance preferably has a high value for the inductance. It may be formed by an electrical coil, which preferably comprises a magnetizable core, for example, an iron yoke, which is formed of individual sheets which are electrically insulated from each other, a ferrite material of a magnetizable material and / or the like.

The energy storage converter is a DC / DC converter, which is preferably designed as a clocked energy converter. It allows bidirectional energy conversion to both supply and remove energy from the energy store. It thus serves as electrical coupling between the DC intermediate circuit and the energy storage. It can be called both as a step-down converter, but also as a boost converter, also called "booster", or as a combination circuit thereof.

The motor vehicle is an electrically driven motor vehicle which can be driven by means of the electric drive. In addition, of course, a further drive unit may be provided, such as an internal combustion engine. Such a vehicle is referred to as a hybrid vehicle.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention. In the figures, like reference numerals designate like components and functions.

Showing:

1 A schematic block diagram representation of a prior art electrical system based on a DC link,

2 A schematic block diagram representation of an electrical system according to the prior art based on a DC link, in which the DC link exclusively electrically couples an accumulator to an inverter,

3 A schematic block diagram representation of an electrical system according to the invention based on a DC link, in which the DC link electrically coupled both an accumulator and a fuel cell with an inverter and the fuel cell by means of a decoupling element from the DC link is decoupled, and

4 A schematic block diagram representation of an alternative decoupling element according to the invention.

1 shows a schematic block diagram representation of an electrical system 10 based on a DC voltage intermediate circuit 20 according to the prior art. To the DC voltage intermediate circuit 20 is a DC / DC converter 14 connected in turn to a fuel cell 12 connected. In addition, it is parallel to the DC / DC converter 14 at the DC voltage intermediate circuit 20 another DC / DC converter 16 connected in turn to an accumulator 18 connected. The DC voltage intermediate circuit 20 is also to an inverter 22 connected, in turn, to a rotating electrical machine 24 connected. The electric machine 24 serves as a drive unit for an electrically driven motor vehicle, which is not shown. In the present case it is provided that the DC / DC converter 14 . 16 Boosters are also called "boosters". With the DC / CD converter 14 It also ensures that the fuel cell 12 is not charged with electrical energy.

2 shows in a schematic block diagram representation of an electrical system 50 whose topology is based on a DC link 28 instead of the DC intermediate circuit 20 of the 1 based. The DC link 28 has a DC link inductance 44 at the same time from one to the DC link 28 connected DC / DC converter 30 used for the purpose of energy conversion. The DC / DC converter 30 is in turn to an accumulator 18 connected as energy storage. The DC / DC converter 30 is designed for bidirectional energy conversion, so that in addition to providing energy in a motor operation and a recuperation operation by inclusion in a regenerative operation of electrical energy by the accumulator 18 is possible.

To the DC link 28 is also an inverter 32 connected to the DC link 28 supplied with direct current (I _LDC ). The inverter 32 produces a three-phase alternating current network, for the purpose of which a half-bridge of two semiconductor switches S1, S2, S3, S4, S5, S6 connected in pairs in series is provided for each phase. In each case one phase of the three-phase alternating current network is provided at the respective center connections, to which via filter capacities 34 an electric machine 24 connected. The electrical system 50 is designed for recuperative operation. The electric machine 24 is in 2 shown in the equivalent circuit diagram with their replacement impedances and voltage sources.

3 now shows a further development of the electrical system 50 in the form of an electrical system 46 , The electrical system 46 according to 3 is different from the electrical system 50 according to 2 in that in addition a fuel cell 12 as an energy source via a decoupling unit 26 to the DC link 28 connected. The other building units correspond to those already in 2 are shown. In this regard, the comments on the embodiment according to 2 directed.

To the fuel cell 12 to protect against undesired effects of energy supply, is the decoupling unit 26 provided by means of a decoupling of the fuel cell 12 is possible when the fuel cell 12 the DC link 28 does not supply electrical energy. This is achieved by means of the decoupling unit 26 in series with the fuel cell 12 a semiconductor diode 48 is connected as a decoupling element. This ensures that a flow of energy only from the fuel cell 12 in the DC link 28 can be done. A reversible energy flow is through the semiconductor diode 48 prevented. This ensures that in Rekuperationsfall by means of the electric machine 24 over the inverter 32 in the DC link 28 fed electrical energy not the fuel cell 12 but instead via the DC / DC converter 30 as an energy storage converter the accumulator 18 is supplied, which can store the supplied energy.

4 schematically shows in block diagram representation a further embodiment for a decoupling unit according to the invention, namely in the form of the decoupling unit 36 , This points next to the semiconductor diode 48 another semiconductor diode 40 also in series with the fuel cell 12 is switched. By the with the decoupling unit 36 provided circuit arrangement, the fuel cell 12 bipolar from DC link 28 be separated because each one of the semiconductor diodes 40 . 48 at one of the two Connections of the fuel cell 12 is connected in series. Nevertheless, it should be noted that the decoupling unit 36 due to the higher number of decoupling elements 40 . 48 higher forward losses than the decoupling unit 26 comprising only the semiconductor diode 48 has as the only decoupling element.

In addition, as an alternative or in addition instead of the semiconductor diodes as decoupling elements of course, reverse blocking semiconductor switches could be used. However, it should be noted that a corresponding control effort is required in order to realize the desired decoupling function.

Thus, with the invention, a recuperation capability for parallel use of energy stores with energy sources can be achieved even for a DC intermediate circuit, which itself can not absorb any energy without being damaged. In addition, by the shared coil through the DC link and the DC / DC converter, the component cost can be reduced. Overall, through the use of a DC intermediate circuit increased power can be provided to the electric machine, at the same time symbiosis effects can be used to save components. In addition, there are overall efficiency advantages.

The embodiments are only illustrative of the invention and are not limiting for these. It should also be noted that the advantages and features and embodiments described for the device according to the invention apply equally to the corresponding method and vice versa. In particular, corresponding device features and vice versa can be provided for device features.

LIST OF REFERENCE NUMBERS

10

Electrical system

12

fuel cell

14

DC / DC converter

16

DC / DC converter

18

accumulator

20

Dc link

22

inverter

24

electric machine

26

Entkoppeleinheit

28

DC link

30

DC / DC converter

32

inverter

34

filter capacity

36

Entkoppeleinheit

40

Semiconductor diode

44

intermediate-

46

Electrical system

48

Semiconductor diode

50

Electrical system

I _LDC

direct current

S1

Semiconductor switches

S2

Semiconductor switches

S3

Semiconductor switches

S4

Semiconductor switches

S5

Semiconductor switches

S6

Semiconductor switches

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6321145 [0002, 0003]
• DE 102013014388 A1 [0003, 0003, 0004]

Claims (7)

Electrical system ( 46 ) for an electrically driven motor vehicle, with an inverter ( 32 ), on which a rotating electrical machine ( 24 ) can be connected to drive the motor vehicle, with an adapted for a bidirectional energy conversion electrical energy storage converter ( 30 ) for connecting an electrical energy store ( 18 ) and with one a DC link inductance ( 44 ) having DC link ( 28 ) for electrically coupling the inverter ( 32 ) with the energy storage converter ( 30 ), wherein the electrical energy storage converter ( 30 ), the DC link inductance ( 44 ) for converting the electrical energy, characterized by a to the DC link ( 28 ) connected decoupling unit ( 26 . 36 ) for connecting an electrical energy source ( 12 ), wherein the decoupling unit ( 26 . 36 ) is formed, the electrical energy source ( 12 ) electrically from the DC link ( 28 ) to decouple when the energy source ( 12 ) the DC link ( 28 ) does not supply electrical energy. Electrical installation according to claim 1, characterized in that the decoupling unit ( 26 ) at least one diode ( 48 ) connected in series to the electrical energy source ( 12 ) is switched. Electrical system according to claim 1 or 2, characterized in that the decoupling unit has at least one reverse-blocking semiconductor switching element. Electrical installation according to one of Claims 1 to 3, characterized in that the electrical energy source ( 12 ) has two electrical connections and the decoupling unit ( 36 ) is designed for bipolar decoupling. Electrical installation according to one of claims 1 to 4, characterized in that the energy source ( 12 ) comprises a fuel cell. Method for operating an electrical system ( 46 ) of an electrically driven motor vehicle, wherein the motor vehicle by means of an inverter ( 32 ), rotating electrical machine ( 24 ), for what purpose the inverter ( 32 ) via a DC link inductance ( 44 ) having DC link ( 28 ) with an electrical energy store ( 18 ) is electrically coupled, wherein the coupling by means of a designed for bidirectional energy conversion electrical energy storage transducer ( 30 ), which the DC link inductance ( 44 ) is used for converting the electrical energy, characterized in that a via a decoupling unit ( 26 . 36 ) to the DC link ( 28 ) connected electrical energy source ( 12 ) by means of the decoupling unit ( 26 . 36 ) from the DC link ( 28 ) is electrically decoupled when the electrical energy source ( 12 ) the DC link ( 28 ) does not supply electrical energy. Method according to claim 6, characterized in that the electrical energy source ( 12 ) by means of the decoupling unit ( 36 ) is decoupled bipolar.

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