DE102017008840A1 - Electric vehicle electrical system - Google Patents

Abstract

The invention relates to an electrical vehicle electrical system (10) for a motor vehicle which can be driven by at least one electric machine (12), with a vehicle battery (14), a cycled energy converter (16) for acting on the electric machine (12) in an intended driving operation of the motor vehicle an electrical machine voltage (18), wherein the clocked energy converter (16) has a DC intermediate circuit (20) which is electrically coupled to the vehicle battery (14) and which has at least one Y-capacitor (22) for producing an electromagnetic compatibility, and with an alternating voltage charging unit (24) connected to the vehicle battery (14), which is designed to be charged to a charging station external of the motor vehicle and charged with a charging AC voltage, the DC link (20) being electrically connected to the vehicle battery (14) by means of a switching unit (28) coupled is, wherein the switching unit (28) is adapted to electrically isolate the DC intermediate circuit (20) when charging the vehicle battery (14) by means of the AC charging unit (24) of the vehicle battery (14).

Description

The invention relates to an electrical vehicle electrical system for a drivable with at least one electric motor vehicle, with a vehicle battery, a clocked energy converter for applying the electrical machine in a normal driving operation of the motor vehicle with an electrical machine voltage, wherein the clocked energy converter has a DC intermediate circuit, with the Vehicle battery is electrically coupled and having at least one Y-capacitor for producing electromagnetic compatibility, and connected to the vehicle battery AC charging unit, which is designed to be connected to a charging station external to the vehicle and charging station side charged with a charging AC voltage.

Generic electrical vehicle electrical systems of motor vehicles and motor vehicles are basically well known in the art, so it does not require a separate printed evidence for this. Motor vehicles usually have an electrical system that includes electrical equipment and units. The electrical system serves to electrically couple the electrical devices and units with each other in a predeterminable manner.

At least part of the electrical devices or units are connected to the electrical system. The electrical system thus serves to distribute the electrical energy within the motor vehicle. Not only but especially in electrically driven vehicles, it is also necessary, at least in certain time periods to supply the motor vehicle with electrical energy for normal operation. For this purpose, the electrical system is electrically coupled by means of the AC charging unit or even by means of a DC charging unit with the motor vehicle external charging station. In the coupled state, which can be produced, for example, by a line-connected electrical connection to the charging station, electrical energy can be supplied to the motor vehicle, in particular the vehicle battery, by the charging station.

Just electrically driven motor vehicles usually have an electric drive device which at least partially serves the intended driving operation of the motor vehicle. So that the motor vehicle can be supplied with electrical energy in the intended driving operation, the electrical system generally comprises an electrical energy storage, here the vehicle battery, which is preferably in the manner of a battery, for example by a high-voltage battery or the like. During the intended driving operation, the energy content of the vehicle battery is reduced over time, whereby charging of the vehicle battery is required upon reaching a predetermined lower state of charge. The electrical energy required for this purpose is provided by the charging station, for which purpose the motor vehicle is parked at the charging station during the supply of electrical energy and is electrically coupled thereto.

The electrical energy is presently made available by means of the charging station, which in turn can be connected to an electrical energy source, preferably to a public power grid or alternatively or additionally to an electric generator, to a solar system, to a wind turbine and / or the like. Via a connecting line, which can be detachably connected to the respective charging unit or to the charging station, the electrical energy can be supplied to the electrical system and stored in the vehicle battery.

Electrically driven motor vehicles are extensively known in the art, so that in this regard a separate documentary proof also does not need. An electrically drivable motor vehicle is a rail-bound vehicle, which has the electric drive device by means of which the electrically drivable motor vehicle can be driven at least partially in the intended driving operation. For this purpose, the electric drive device usually has one or more rotating electrical machines which can be controlled in a predeterminable manner by means of a suitably designed energy converter. For this purpose, the energy converter is designed to provide a respective machine voltage for the rotating electrical machines. Such an energy converter may be, for example, an inverter, a DC-DC converter, for example a DC / DC converter, and / or the like.

An electrically drivable motor vehicle is preferably an electric vehicle or a hybrid vehicle. In an electric vehicle, the electric drive device is usually the only device that serves the driving operation of the motor vehicle. In contrast, in a hybrid vehicle, a further drive device is usually present, which can usually be configured in the form of an internal combustion engine. The internal combustion engine can also be used for the intended driving operation, as the electric drive device. Both drive devices can also be operated in combination with one another. The motor vehicle is in particular a motor vehicle, preferably a passenger car.

In order to comply with requirements with regard to the electromagnetic compatibility and also of network perturbations, in particular during a charging process with DC voltage, it has hitherto been customary to arrange a corresponding filter unit in the motor vehicle on the DC voltage side, usually tightly in the case of a charging socket or integrated into the charging socket. Both the filter unit and the electrical devices and units of the electrical system, in particular when they are operated with high voltage, usually have to produce the electromagnetic compatibility via Y-capacitors. Such Y capacitors may also be provided on the charging station side, as a rule, when a DC voltage is used for charging. The effect of Y-capacitors in the field of electromagnetic compatibility, in particular the sparking disturbance, is known to the person skilled in the art, so there is no need for a separate further explanation in this regard. For the rest, reference is made to the relevant standardization, such as the Directive 2014/30 / EU about the electromagnetic compatibility, EN 61000 and more.

For electrical safety reasons, the electrical energy stored in all Y capacitors should not exceed a predetermined maximum value. This regularly leads to a structural design that capacitance values of the Y capacitors are usually selected to be smaller on the motor vehicle side than necessary for the proper production of the electromagnetic compatibility, in particular with regard to electrical devices and units connected to the electrical system would.

In current electrically driven vehicles, such as electric vehicles, hybrid vehicles or the like, in which the electrical system is supplied with high voltage, are in the electrical equipment or units, for example in an inverter drive means of the motor vehicle, to which the rotating electric machine for the purpose of driving the motor vehicle is connected, corresponding filter units provided by which leads can be suppressed, so that in a shielded line system of the electrical system, a maximum permissible level of interference or predetermined by the electromagnetic compatibility limits can be met.

A special situation arises as soon as the motor vehicle is electrically coupled to a charging station in order to be able to supply the vehicle battery with electrical energy. In this case, additional requirements relating to the electromagnetic compatibility and system perturbations of the charging infrastructure of the charging station must be considered. In addition, it should be noted that for the production of a line-connected energy coupling between the motor vehicle and the charging station, charging cables are increasingly being used which have no shielding. In order to comply with such arrangements, the requirements in terms of electromagnetic compatibility and the network perturbations, for example, a DC voltage filter unit is provided on the motor vehicle side of the DC charging socket.

However, it has proven to be problematic when the motor vehicle is to be charged by means of an AC voltage from the charging station. In this case, the total capacity of Y capacitors provided on the vehicle side proves to be an obstacle, because these capacitors can cause a leakage current, which can lead to fault initiation on the charging station side and / or can exceed a permissible value for leakage currents in electrical systems, as described, for example, in US Pat standardization is specified, for example in the Standard DIN EN 61800 or the like. This problem can basically be solved only by reducing the capacitance values of the Y-capacitors provided in the motor vehicle, it being noted, however, that this can considerably increase the expense for the filter units.

The invention has for its object to improve an electrical system to the effect that the use of Y-capacitors is improved.

As a solution, an electrical system according to the independent claim 1 is proposed with the invention.

Advantageous developments emerge by features of the dependent claims.

The invention particularly proposes that the DC voltage intermediate circuit is electrically coupled to the vehicle battery by means of a switching unit, wherein the switching unit is designed to electrically disconnect the DC intermediate circuit when the vehicle battery is charged by means of the AC charging unit from the vehicle battery.

The invention is based on the aspect that electrical devices or units of the electrical system, in particular the DC voltage intermediate circuit, are supplied with a DC voltage and Y-capacitors usually cause no problems with regard to a leakage current here. This problem usually arises only when the Y capacitors are charged with an alternating voltage, and this can occur, for example, when an AC voltage is used to charge the vehicle battery, for example, compared to the reference potential to which the Y capacitors are connected , is not galvanically isolated. The reference potential may be, for example, a vehicle ground, a ground potential or the like.

The invention makes use of the idea of electrically separating the Y capacitors provided on the intermediate side by means of the switching unit from the vehicle battery, so that they are electrically separated from the vehicle battery via the AC charging unit and thus do not need to be supplied with alternating voltage. As a result, results for the electrically isolated by means of the switching unit Y capacitors that they are not able to contribute to any leakage current. As a result, it is possible to dimension the Y capacitors on the vehicle side and to design filters accordingly, without the leakage current problem needing to be considered at least for the Y capacitors, which can be electrically decoupled from the vehicle battery by means of the switching unit or can be switched off. As a result, the overall filter effort can also be optimized for DC operation, in particular for charging by means of the DC charging unit with respect to further requirements, so that a good filter function can be achieved with little effort.

The shutdown of the Y capacitors can also be provided for charging by means of the DC charging unit. By doing so, it can be achieved that an electric charge which may be stored in the Y capacitors does not lead to dangerous states with respect to a touch by a person or the like. By switching off the Y capacitors, contact of contacts of the charging socket can be made more safely, in particular if the electrical system is designed as an electrically insulated vehicle electrical system, for example in the manner of an IT network or the like. In particular, the risk of electric shock can be reduced.

By allowing a majority of the Y capacitors, if not all of the Y capacitors, to be electrically disconnected from the vehicle battery during charging of the vehicle battery with the AC charger, the electrical safety and electromagnetic compatibility requirements may be specific for charging be optimized with the AC charging unit. As a rule, it is not necessary for the charging process to supply electrical devices or units, in particular the clocked energy converter, with electrical energy from the vehicle battery, especially since the motor vehicle has to be positioned during the charging of the vehicle battery at the charging station. Otherwise, the line-based energy-related coupling would usually not be feasible.

The clocked energy converter is preferably adapted to the electric machine, so that it can be acted upon in normal operation with a suitable machine voltage. If the electrical machine is an AC voltage machine, the clocked energy converter is preferably designed as an inverter. In a polyphase AC machine, the inverter may be configured to provide a respective one of the multiple phases of the polyphase AC voltage. Such an electric machine may be, for example, an asynchronous machine, a synchronous machine or the like. If the electric machine is a DC voltage machine, the clocked energy converter can be designed as a DC / DC converter.

The AC charging unit comprises, in addition to an AC voltage terminal to which the charging station can be connected to provide the AC voltage, a rectifier unit, which can be designed as a half-wave rectifier, as a full wave rectifier, as a bridge rectifier, as well as in conjunction with a clocked energy converter or the like. The AC charging unit is preferably connected directly to the vehicle battery. It is designed in particular to be able to provide an unidirectional electrical energy coupling for performing the charging can. If, on the other hand, bidirectional energy coupling is to be made possible, it can be provided that the AC charging unit has a suitable clocked energy converter, in particular an inverter. The charging AC voltage may comprise a single-phase or else a polyphase, preferably a three-phase, AC voltage. For example, the AC charging voltage may be a single-phase AC charging voltage that is sinusoidal and has an RMS voltage of about 230 V at an AC frequency of about 50 Hz. In a three-phase AC voltage can be provided that at an AC voltage frequency of about 50 Hz, an AC voltage in the amount of effectively 400 V is present. The AC charging unit is adapted to the charge AC voltage provided by the charging station.

The term "high voltage" includes an electrical voltage that is greater than about 60 volts. Preferably, the term high voltage is compliant with Standard ECE R 100 ,

Furthermore, the electrical system can comprise a DC charging unit which is connected to the DC voltage intermediate circuit and which is designed to be connected to the charging station external of the motor vehicle and to be charged with charging DC voltage on the charging station side. The DC charging unit can, if no voltage adjustment is required, comprise only electromechanical connecting elements with which the loading station side provided DC charging voltage can be passed to the DC link. If, however, a voltage adjustment is required, it can be provided that the DC charging unit comprises a suitable DC / DC converter. The DC charging unit is preferably connected directly to the DC voltage intermediate circuit, so that it can be separated from the vehicle battery by means of the switching unit. The fact that the DC charging unit is connected to the DC voltage intermediate circuit, there is no need to directly own electrical connection with the vehicle battery to pass. The vehicle battery can be charged here during a charging process by means of a DC charging voltage via the DC intermediate circuit. For this purpose, the switching unit establishes an electrical connection between the vehicle battery and the DC voltage intermediate circuit. As already explained above, no significant restrictions need to be taken into account for the design of the Y capacitors with regard to leakage currents, since in the case of a capacitor charged with a DC voltage, there is generally essentially no current flow.

The switching unit has at least so many switching elements that the DC voltage intermediate circuit can be reliably electrically separated from the vehicle battery. For this purpose, the switching unit preferably comprises at least two switching elements, wherein one of the switching elements is able to separate a positive potential of the vehicle battery and the DC intermediate circuit, whereas a second of the at least two switching elements is arranged to electrically disconnect a negative potential of the vehicle battery and the DC intermediate circuit. Preferably, the two switching elements are switched together, in particular synchronously. It is particularly advantageous if, by controlling the switching states of the switching elements of the switching unit, the Y capacitors connected to the DC voltage intermediate circuit can be switched off when the alternating voltage charging unit is used by means of the switching unit. As a result, these Y capacitors can no longer have a negative effect with respect to the generally required electrical safety with regard to leakage currents, as described above. Thus, only Y-capacitors are active, which are directly electrically coupled to the vehicle battery or which are provided in the AC charging unit in order to be able to achieve, for example, a charging station-side adaptation with regard to electromagnetic compatibility, in particular with regard to conducted radio interference or the like. Overall, the invention thus allows to design the electrical system of the motor vehicle largely independent of requirements for Y-capacitors with respect to leakage currents. Especially for the relevant case of charging the vehicle battery by means of AC voltage, the negative effects of Y capacitors can be significantly limited, if not completely avoided.

By suitable arrangement of the switching unit between the vehicle battery and the DC intermediate circuit can be disconnected by means of the switching unit when charging the vehicle battery by means of the AC charging voltage of the DC intermediate circuit, which may include the clocked energy converter and the filter unit for DC charging and the rotating electrical machine. Y capacitors of the aforementioned components therefore do not contribute to the total capacity of the Y capacitors when charging by means of the AC voltage. This makes it possible for the remaining components of the on-board electrical system, for example high-voltage components, to be chosen to have larger Y capacitors which may be required, so that improved electromagnetic compatibility can be achieved, in particular with regard to spark interference, preferably line-bound radio interference.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or alone in the single figure can be used not only in the respectively indicated combination but also in other combinations or alone, without the frame to leave the invention.

It shows the only Fig. A schematic diagram representation of an electrical system according to the invention.

It shows the only Fig. An electrical system 10 a not shown electrically driven motor vehicle, which in the present case is an electric vehicle. The electrical system 10 includes a vehicle battery 14 , Which in the present case is formed by a high-voltage battery, which is designed as a lithium-ion battery. In addition, the electrical wiring system includes 10 an inverter 16 as a clocked energy converter, in an intended driving operation of the motor vehicle, an electric machine 12 with an electrical machine voltage 18 applied. In the present case is the electric machine 12 a three-phase synchronous machine, which is why the inverter 16 as machine voltage 18 provides a corresponding three-phase machine AC voltage.

The inverter 16 has a DC voltage intermediate circuit 20 on, in a known manner an intermediate circuit capacitor 34 includes. The DC voltage intermediate circuit 20 is, as will be shown below, with the vehicle battery 14 electrically coupled. Furthermore, the intermediate circuit comprises 20 two Y capacitors 22 connected to a respective connection to one of the two electrical potentials of the DC intermediate circuit 20 are connected and with their respective other connection to a reference potential 36 are connected. The reference potential 36 is presently formed by a metal housing which is electrically connected to a vehicle ground (not shown). The housing comprises the DC intermediate circuit 20 as well as the inverter 16 as well as the Y capacitors 22 ,

To each of the Y capacitors 22 is a respective electrical resistance 38 connected in parallel, which serves, if necessary, the Y-capacitors 22 to be able to unload. This can be provided, for example, when the electrical system 10 to be taken out of service due to maintenance and / or the like. This is to avoid dangerous voltages even after a decommissioning of the electrical system 10 continue to apply.

Inside the case, which is the reference potential 36 is also a filter unit 32 arranged for the production of electromagnetic compatibility. This filter unit 32 is at the DC voltage intermediate circuit 20 connected. At the same time, the filter unit provides 32 also a connection to the vehicle battery 14 ready. The filter unit 32 may contain other Y capacitors to achieve a good interference suppression radio noise and / or the like as needed.

To the DC voltage intermediate circuit 20 is also a DC charging unit 26 connected, which is designed to be connected to a motor vehicle external charging station and charging station side charged with a DC charging voltage. The DC charging unit 26 preferably has its own filter unit, not shown further. About the DC charging unit 26 can the vehicle battery 14 thus electrical energy is supplied. The DC charging unit 26 includes a charging socket, not shown, via a switching unit 42 by electromechanical switching elements S3, S4 galvanic in loading case with the DC intermediate circuit 20 coupled and again from the DC voltage intermediate circuit 20 can be electrically disconnected when the DC charging unit 26 is disabled or not used. The switching unit 42 serves among other things, not designated terminal contacts of the DC charging unit 26 outside the charging mode by means of the charging DC voltage, so that there can be no dangerous electrical voltage. For example, touch protection can be achieved or improved.

The vehicle battery 14 , which is designed here for a rated voltage of about 450 V, is by means of another switching unit 28 , the switching elements 30 (S1, S2), to that of the filter unit 32 provided connection connected. By means of the switching unit 28 can the vehicle battery 14 with the DC intermediate circuit 20 be electrically coupled. To the vehicle battery 14 are also high voltage ancillaries 40 connected, which are not further referred to herein, but may include conventional units of the motor vehicle that can be operated with high voltage, such as an air conditioning compressor or the like.

Furthermore, on the high-voltage battery 14 an AC charging unit 24 connected, which is also designed to be connected to a motor vehicle external charging station. The AC charger 24 is further configured to be charged on the charging station side with a charging AC voltage. In the present case, it is provided that the AC charging unit 24 is designed to be charged with a charging AC voltage of effectively about 230 V at an AC voltage frequency of about 50 Hz. The AC charger 24 provides in this regard a separate charging socket ready. Basically, instead of a single-phase AC charging voltage, a polyphase, in particular a three-phase AC charging voltage can be provided. Depending on availability, the AC frequency as well as the RMS value of the AC voltage can vary. The AC charger 24 can be designed accordingly adapted for this purpose.

To the Y capacitors 22 during a charging operation by means of the AC charging unit 24 to disable is the switching unit 28 formed, the DC intermediate circuit 20 when charging the vehicle battery 14 by means of the AC charging unit 24 from the vehicle battery 14 to disconnect electrically. For this purpose, the switching elements 30 actuated and moved into an open switching state, so that in the present case a galvanic isolation can be achieved. The switching elements 30 are presently designed as electromechanical switching elements, which can be controlled in the manner of a relay by means of a suitable control signal of a control unit, not further shown. In a corresponding manner, of course, the switching elements S3 and S4 of the switching unit 42 be controlled if necessary by means of the control unit.

Not shown is that the switching unit 28 with a detection unit, not shown, for detecting an operation of the AC charging unit 24 communication technology is coupled. The detection unit is designed depending on an operation of the AC charging unit 24 to provide an AC charging signal. The switching unit 28 is formed accordingly, the off state, in which the switching elements 30 in the open state, depending on the AC charging signal to activate. This takes place here regardless of whether the DC charging unit 26 is activated.

In this way it can be ensured that otherwise for charging by means of the AC charging unit 24 unfavorable Y capacitors 22 cause a leakage current greater than a permissible value. Of course, there is the possibility of the Y capacitors 22 correspondingly small in terms of their capacity value. However, it should be remembered that the Y capacitors 22 then only a very reduced effect for the production of electromagnetic compatibility able to provide, which is why the Y capacitors 22 For this reason, it should be better to have as much capacity as possible. By the invention, a decoupling can be achieved, so that the dimensioning of the Y capacitors 22 largely independent of requirements with respect to the leakage current during electrical charging of the vehicle battery 14 by means of the AC charging unit 24 can be achieved.

The embodiment shown in the figure is merely illustrative of the invention and is not intended to limit this. Of course, apply to the electrical system according to the invention 10 stated advantages and effects alike for one with the electrical system 10 equipped motor vehicle.

LIST OF REFERENCE NUMBERS

10

electrical wiring system

12

electric machine

14

vehicle battery

16

energy converters

18

electrical machine voltage

20

Dc link

22

Y-capacitor

24

AC charger

26

DC charger

28

switching unit

30

electromechanical switching element

32

descrambler

34

Link capacitor

36

reference potential

38

resistance

40

High-voltage accessory

42

switching unit

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 non-patent literature

• Directive 2014/30 / EU [0008]
• EN 61000 [0008]
• Standard DIN EN 61800 [0012]
• Standard ECE R 100 [0023]

Claims (5)

Electrical wiring system ( 10 ) for a with at least one electric machine ( 12 ) drivable motor vehicle, with a vehicle battery ( 14 ), a clocked energy converter ( 16 ) for applying the electric machine ( 12 ) in a proper driving operation of the motor vehicle with an electrical machine voltage ( 18 ), wherein the clocked energy converter ( 16 ) a DC voltage intermediate circuit ( 20 ) connected to the vehicle battery ( 14 ) is electrically coupled and for producing an electromagnetic compatibility at least one Y-capacitor ( 22 ), and with a to the vehicle battery ( 14 ) connected AC charging unit ( 24 ), which is designed to be connected to a charging station external of the motor vehicle and to be charged with a charging AC voltage on the charging station, characterized in that the DC voltage intermediate circuit ( 20 ) by means of a switching unit ( 28 ) with the vehicle battery ( 14 ) is electrically coupled, wherein the switching unit ( 28 ) is formed, the DC voltage intermediate circuit ( 20 ) when charging the vehicle battery ( 14 ) by means of the AC charging unit ( 24 ) from the vehicle battery ( 14 ) to be separated electrically. Electrical vehicle electrical system according to claim 1, characterized in that the switching unit ( 28 ) at least one electromechanical switching element ( 30 ) having. Electrical vehicle electrical system according to one of the preceding claims, characterized by a with the switching unit ( 28 ) communication-coupled detection unit for detecting an operation of the AC charging unit ( 24 ), wherein the detection unit is formed, depending on an operation of the AC charging unit ( 24 ) to provide an AC charging signal, and wherein the switching unit ( 28 ) is adapted to activate an off state depending on the AC charging signal. Electrical vehicle electrical system according to one of the preceding claims, characterized by a DC charging unit ( 26 ) connected to the DC voltage intermediate circuit ( 20 ) is connected and which is designed to be connected to the motor vehicle external charging station and charging station side charged with a DC charging voltage. Electric vehicle electrical system according to claim 4, characterized in that the switching unit ( 28 ) is formed, the switch-off state regardless of an operation of the DC charging unit ( 26 ) to activate.

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