DE102018000578A1 - Electrical coupling of a vehicle electrical system of a motor vehicle with a charging station - Google Patents

Abstract

The invention relates to an energy coupling device (10) for electrically coupling an electrical system (12) of a motor vehicle with a charging station (14) providing an electrical alternating voltage external to the motor vehicle, with a bridge rectifier (16) which can be electrically coupled to the charging station (14) and rectifies the AC voltage. comprising a DC voltage terminal (18) which is electrically coupled to a DC intermediate circuit (20) of the electrical system (12), characterized by a DC voltage converter (22) having a first terminal (24) with the DC voltage terminal (18) and with a second Terminal (26) to the DC voltage intermediate circuit (20) of the electrical system (12) is electrically coupled, wherein the DC-DC converter (22) is formed, electrical potentials (28, 30) at the second terminal (26) for the DC intermediate circuit (20) provided DC link voltage (32) with respect to a specifiable electr Set reference potential (34) to predetermined, substantially constant values.

Description

The invention relates to an energy coupling device for electrically coupling a vehicle electrical system of a motor vehicle with a charging station providing an electrical alternating voltage, with a charging station electrically coupled to the rectifier bridge rectifier rectifier having a DC voltage terminal which is electrically coupled to a DC voltage intermediate circuit of the electrical system. Furthermore, the invention relates to a method for electrically coupling a vehicle electrical system of a motor vehicle with a motor vehicle external, an electrical alternating voltage providing charging station in which an AC voltage of the charging station rectified by means of an electrically dockable with the charging station and rectifying the AC rectifying bridge rectifier and rectified at one with a DC voltage intermediate circuit of the electrical system electrically coupled DC voltage connection is provided.

Generic energy coupling devices as well as generic methods are extensively used in the prior art and find particular use when an electrical system of a motor vehicle with the motor vehicle charging station is to be electrically coupled, for example, to be able to supply electrical power to the electrical system of the motor vehicle. By means of the energy coupling device, the different electrical properties of the charging station and the electrical system can be adjusted so that a reliable specifiable energy transfer can be made possible. Such electrical power coupling devices and also methods for their operation are frequently used in motor vehicles, especially those motor vehicles which are designed to be electrically drivable.

A generic energy coupling device is used in particular to produce an electrical coupling when the charging station provides an AC voltage. Usually, the electrical system of the motor vehicle is designed for the application of a DC voltage. It is therefore necessary a corresponding rectification to allow energy transfer. This achieves the coupling device of the prior art in that a rectifier unit is provided, which is usually designed as a bridge rectifier. The bridge rectifier can be used in a particularly simple manner an efficient use of the AC voltage during rectification. In addition, of course, other variants of the rectification are of course possible, for example, a half-wave rectification, a full-wave rectification and / or the like. However, these generally prove to be less favorable compared to a bridge rectifier, in particular also with regard to the use of the AC voltage, which is why they have found no distribution, especially in the field of motor vehicles.

A bridge rectifier is a specific rectifier circuit, which is usually formed using four switching elements connected in a predetermined circuit arrangement. Usually, the switching elements are formed by diodes. In the case of specific bridge rectifiers, switching elements, in particular semiconductor switches, for example transistors or the like, may be provided instead of or in addition to the diodes. Incidentally, the diodes themselves may also be formed by switching elements, for example, transistors, thyristors, combination circuits thereof, or the like.

Electric vehicle electrical systems as well as motor vehicles with such electrical electrical systems are well known in the art. For example, the US 2010/0076636 A1 a vehicle with an electrical system. The electrical system includes several batteries in the manner of accumulators that can be electrically charged independently. To this end, the doctrine of US 2010/0076636 A1 corresponding energy converter on the type of DC / DC converters, with which a corresponding specifiable energy technology coupling can be achieved.

Motor vehicles usually have an electrical system, which includes electrical equipment and electrical units. The electrical system serves to electrically couple the electrical devices and the electrical units with each other in a predeterminable manner. At least a part of the electrical devices or electrical units is 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 is usually provided at least that the electrical system has a DC voltage intermediate circuit, which is designed to be subjected to a DC voltage in the high-voltage range. The term "high voltage" includes a DC electrical voltage that is greater than about 60V. Preferably, the term "high voltage" conforms to the standard ECE R 100.

Especially in electrically driven motor vehicles, the electrical system is designed for admission in the "high voltage". For example, the electrical system with a DC voltage of about 800 V or with a DC voltage of about 400 V be applied. Of course, the values of the DC voltage can also be chosen differently. In principle, however, the aforementioned voltage values result in consideration of standardized components and electrical devices which are designed for such electrical voltages.

For reasons of electrical safety is usually a galvanic connection between the charging station and the electrical system of the motor vehicle, especially in the "high voltage", usually not desired or not allowed. For this reason, a galvanically isolated DC / DC converter is usually provided in the prior art, which provides an electrical coupling between the provided by the bridge rectifier DC voltage and the DC voltage intermediate circuit of the electrical system.

Even if the state of the art has proven itself in this respect, problems still show up. In particular, if an insulation fault occurs between the bridge rectifier and the galvanically separated DC / DC converter, there is a risk of undesired leakage currents, which not only can result in dangerous electrical potentials, in particular on accessible parts, but can also disturb charging stations on the safety devices. This may be the case, for example, for a residual current circuit breaker, in particular if it is designed according to a type A. In such residual current circuit breakers, as they are usually used in household electrical installations, the problem may arise that due to an aforementioned insulation fault of the residual current circuit breaker with a DC current is applied as a fault current, the function-determining elements, which are based in particular on magnetism, in a saturation, so that the function of the residual current circuit breaker is disturbed. In such a case, electrical safety can no longer be guaranteed. However, since the application of such residual current circuit breakers is widespread and is also used in particular for charging stations, which are used in the domestic sector, for example in private households to charge electrically driven vehicles outside driving, an increased security effort is required here. Basically, of course, there is the possibility, in particular the area of the bridge rectifier to protect the DC / DC converter by means of a double insulation in the electrical sense, for example, as specified in the standard IEC 60335 or the like. However, this is very expensive and causes additional space and weight in a motor vehicle, which is why such a solution is undesirable.

The invention has for its object to improve electrical safety, in particular in a connection of the electrical system of the motor vehicle to a charging station, which provides an electrical alternating voltage.

As a solution, the invention proposes a power coupling device and a method according to the independent claims.

Advantageous developments will become apparent from the features of the dependent claims.

With respect to a generic power coupling device is in particular proposed that this has a DC-DC converter, which is electrically coupled with a first terminal to the DC voltage terminal and a second terminal to the DC voltage intermediate circuit of the electrical system, wherein the DC-DC converter is formed, electrical potentials one at the second terminal for the DC intermediate voltage provided DC voltage with respect to a predetermined electrical reference potential to predetermined, substantially constant values.

With regard to a generic method, it is proposed, in particular, that the bridge rectifier is electrically coupled to the DC intermediate circuit of the vehicle electrical system by means of a DC-DC converter, wherein the DC-DC converter sets electrical potentials of a DC link voltage provided for the DC intermediate circuit to predetermined, substantially constant values with respect to a predeterminable electrical reference potential ,

The invention is based on the idea that when an insulation fault occurs, which relates, for example, to one of the two electrical potentials of the DC link voltage, the leakage current can be reduced by changing the affected potential so that a corresponding DC current is minimized. The adjustment of the electrical potential, in particular of the potential which is affected by the insulation fault, can be realized correspondingly by means of the DC-DC converter. The fact that the electrical potential can be changed so that an electrical voltage between this potential and the reference potential is as low as possible, the leakage current can be correspondingly low. This has the advantage that, inter alia, protective devices such as residual current circuit breakers are no longer overly charged with an impermissible direct current, so that their function is no longer disturbed. As a result, the overall electrical safety can be substantially improved.

The reference potential may be, for example, a vehicle ground. However, it is particularly advantageous for a ground potential, which can be coupled in particular when producing a wired electrical connection between the charging station and the motor vehicle with the vehicle mass.

The invention also makes it possible to reduce effects caused by limited electrical isolation, for example, leakage currents. Such leakage currents can be caused, for example, by Y capacitors which are connected to the electrical potentials of the DC link voltage in order to be able to produce, for example, the electromagnetic compatibility.

To provide an electrical insulation between the electrical potentials of the DC link voltage relative to the reference potential is usually an isolation device. The isolation device can be formed by, for example, electrically insulating materials being arranged between the reference potential and the potentials of the intermediate circuit voltage, by means of which a desired electrical insulation can be provided. Additionally or alternatively, air can be used as a material of the electrical insulation device, wherein depending on a distance, the desired electrical insulation can be achieved. The DC link voltage thus results from a potential difference of their associated electrical potentials. It proves particularly advantageous if a first electrical potential of the DC intermediate circuit is a negative potential and a second electrical potential of the DC intermediate circuit is a positive potential.

The advantages and effects stated for the energy coupling device according to the invention apply equally to the method according to the invention and vice versa. In this respect, device features can of course also be formulated as process features and vice versa.

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 in the figures alone 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.

• 1 in einer schematischen Blockschaltbilddarstellung eine Ladeeinrichtung für ein Bordnetz eines Kraftfahrzeugs gemäß dem Stand der Technik zum Anschließen an eine Ladestation, die eine dreiphasige Wechselspannung bereitstellt,
• 2 eine schematische Schaltbilddarstellung für eine erste Ausgestaltung für eine Gleichrichtereinheit mit Leistungsfaktorkorrektur für die Ladeeinrichtung gemäß 1,
• 3 eine schematische Schaltbilddarstellung für eine zweite Ausgestaltung für eine Gleichrichtereinheit mit Leistungsfaktorkorrektur für die Ladeeinrichtung gemäß 1,
• 4 eine schematische Schaltbilddarstellung für eine dritte Ausgestaltung für eine Gleichrichtereinheit mit Leistungsfaktorkorrektur für die Ladeeinrichtung gemäß 1,
• 5 eine schematische Schaltbilddarstellung für eine Ausgestaltung für einen galvanisch getrennten DC/DC-Wandler für die Ladeeinrichtung gemäß 1,
• 6 eine schematische Diagrammdarstellung einer elektrischen Spannung zwischen einem Minuspotential nach dem Gleichrichten mit einer Gleichrichtereinheit nach 2 bis 4 gegenüber einem Erdpotential,
• 7 in einer schematischen Blockschaltbilddarstellung eine Ladeeinrichtung für ein Bordnetz eines Kraftfahrzeugs gemäß der Erfindung zum Anschließen an eine Ladestation, die eine einphasige Wechselspannung bereitstellt,
• 8 zwei schematische Diagrammdarstellungen für Spannungsverläufe von elektrischen Spannungen zwischen dem Pluspotential und dem Minuspotential jeweils in Bezug auf das Erdpotential unmittelbar nach dem Gleichrichten bei der Ladeeinrichtung gemäß 7,
• 9 zwei schematische Diagrammdarstellungen für Spannungsverläufe von elektrischen Spannungen zwischen dem Pluspotential und dem Minuspotential in Bezug auf das Erdpotential unmittelbar nach einer Leistungsfaktorkorrektur bei der Ladeeinrichtung gemäß 7,
• 10 zwei schematische Diagrammdarstellungen für Spannungsverläufe von elektrischen Spannungen zwischen dem Pluspotential und dem Minuspotential in Bezug auf das Erdpotential unmittelbar nach einer Spannungswandlung mittels eines ersten Wandlermoduls bei der Ladeeinrichtung gemäß 7,
• 11 zwei schematische Diagrammdarstellungen für Spannungsverläufe von elektrischen Spannungen zwischen dem Pluspotential und dem Minuspotential in Bezug auf das Erdpotential unmittelbar nach einer Spannungswandlung mittels eines zweiten Wandlermoduls bei der Ladeeinrichtung gemäß 7,
• 12 eine schematische Schaltbilddarstellung für einen konventionellen Tiefsetzsteller,
• 13 eine schematische Schaltbilddarstellung für einen Tiefsetzsteller zum Einsatz bei einem der Wandlermodule gemäß 7,
• 14 eine schematische Schaltbilddarstellung für einen konventionellen Hochsetzsteller,
• 15 eine schematische Schaltbilddarstellung für einen Hochsetzsteller zum Einsatz bei einem der Wandlermodule gemäß 7, und
• 16 eine schematische Schaltbilddarstellung für die Ladeeinrichtung gemäß 7.

Showing:

• 1 1 shows a schematic block diagram representation of a charging device for an electrical system of a motor vehicle according to the prior art for connection to a charging station, which provides a three-phase alternating voltage,
• 2 a schematic diagram representation of a first embodiment of a rectifier unit with power factor correction for the charging device according to 1 .
• 3 a schematic diagram representation of a second embodiment for a rectifier unit with power factor correction for the charging device according to 1 .
• 4 a schematic diagram representation of a third embodiment of a rectifier unit with power factor correction for the charging device according to 1 .
• 5 a schematic diagram representation of an embodiment of a galvanically isolated DC / DC converter for the charging device according to 1 .
• 6 a schematic diagram of an electrical voltage between a negative potential after rectification with a rectifier unit according to 2 to 4 opposite a ground potential,
• 7 1 shows a schematic block diagram representation of a charging device for an electrical system of a motor vehicle according to the invention for connection to a charging station, which provides a single-phase AC voltage;
• 8th two schematic diagrams for voltage waveforms of electrical voltages between the plus potential and the negative potential respectively with respect to the ground potential immediately after the rectification in the charging device according to 7 .
• 9 two schematic diagrams for voltage waveforms of electrical voltages between the plus potential and the negative potential with respect to the ground potential immediately after a power factor correction in the charging device according to 7 .
• 10 two schematic diagrams for voltage waveforms of electrical voltages between the plus potential and the negative potential with respect to the ground potential immediately after a voltage conversion by means of a first converter module in the charging device according to 7 .
• 11 two schematic diagrams for voltage waveforms of electrical voltages between the plus potential and the negative potential with respect to the ground potential immediately after a voltage conversion by means of a second converter module in the charging device according to 7 .
• 12 a schematic diagram representation for a conventional buck converter,
• 13 a schematic diagram representation of a buck converter for use in one of the converter modules according to 7 .
• 14 a schematic diagram representation of a conventional boost converter,
• 15 a schematic diagram representation of a step-up converter for use in one of the converter modules according to 7 , and
• 16 a schematic diagram representation of the charging device according to 7 ,

1 shows in a schematic block diagram representation of a charging device 50 as an energy coupling device for electrically coupling a vehicle electrical system 12 a motor vehicle not shown with a motor vehicle external, an electrical three-phase AC voltage charging station 52 , The charging station 52 provides three alternating voltages offset by about 120 ° in one phase L ₁ . L ₁ . L ₃ ready, facing a common connection, namely a zero connection N provides an effective voltage of about 230 V at a frequency of about 50 Hz. The 0 connection N is at the same time also a ground connection, which in the present case is marked PE. The charging station 52 is via a detachable wired connection with the charging device 50 coupled. For this purpose, the motor vehicle during the electrical coupling to the charging station 52 switched off. About known plug connections, a charging cable of the charging station 52 to the charging device 50 be connected.

The charging device 50 provides for each of the AC voltages L ₁ . L ₂ . L ₃ a respective rectifier unit 54 which, in addition to a respective rectification function, also performs a power factor correction based on a bridge rectification. The DC voltage generated here is applied to capacitors 56 each provided. Via respective galvanically isolated DC / DC converters 58 become the ones on the capacitors 56 provided DC voltages to a DC link DC voltage 32 a DC voltage intermediate circuit 20 of the electrical system 12 customized. To the DC link voltage 32 Furthermore, electrical devices or electrical units are connected schematically, which are in 1 present by accumulators 60 are formed. The accumulators 60 in the present case are high-voltage batteries, which are designed for a rated voltage of about 450 V.

With the 2 to 4 are different circuit variants for the rectifier units 54 shown. Each of the rectifier units 54 directs a respective one of the alternating voltage phases L ₁ . L ₂ . L ₃ equal. In the schematic diagram representation according to 2 it is a bridge rectifier with a unidirectional power factor correction and at the same time a voltage transformer. The schematic diagram representation according to 3 refers to a unidirectional totem pole power factor correction rectifier. The schematic diagram representation according to 4 refers to an appropriate circuit like 3 However, this is designed for a bidirectional flow of energy.

5 shows in a schematic diagram representation of the galvanically isolated DC / DC converter 58 ,

Occurs in the area of the capacitors 56 that is, in a circuit area between the rectifier units 54 and the DC / DC converters 58 , an insulation fault, this may under certain circumstances dangerous conditions, especially with respect to the charging station 52 to lead. Is the charging station 52 For example, provided by a private household, is the charging station 52 usually protected by a fault current circuit breaker, usually of type A, against fault currents.

Due to the principle of rectification in the bridge rectification, however, the problem arises that the rectified potentials at the capacitors 56 with the alternating voltage frequency with respect to the ground potential 34 vary. An insulation fault thus leads to a corresponding leakage current, which has at least on average a significant DC component. If a conventional residual current circuit breaker, in particular of the type A, supplied with a DC current as a fault current, a magnetism-based release mechanism can reach saturation and thus be ineffective. The protective function of the residual current circuit breaker is thereby deactivated. That is inadmissible.

One remedy would be to double insulation in the relevant area between the rectifier units 54 and the DC / DC converters 58 form, including a primary side of the DC / DC converter transformers. Instead of the galvanically isolated DC / DC converter 58 Galvanic coupled DC / DC converters used, so the requirement for double isolation on all other components of the electrical system 12 must be transmitted to meet the safety requirements. This would include, for example, the vehicle battery, a powertrain and all, on the electrical system 12 connected, electrical facilities and electrical units.

6 shows in a schematic voltage-time diagram by means of a graph 78, the electrical voltage between the negative potential on one of the capacitors 56 in relation to the earth potential 34 , It can be seen that after rectifying the AC voltage L ₁ . L ₂ respectively L ₃ the negative potential related to the earth potential 34 forms negative sine half-waves. By using the galvanically isolated DC / DC converter 58 this problem is on the area between the rectifier units 54 and the DC / DC converters limited. In the case of the insulation fault described above, this can lead to problems, in particular with regard to the residual current circuit breaker.

7 now shows an embodiment of a charging device 10 as energy coupling device according to the invention, the electrical coupling of the electrical system 12 of the motor vehicle with a motor vehicle external, an electrical alternating voltage P providing charging station 14 serves. As already explained above, the zero connection is also here N with the earth potential 34 electrically connected as reference potential. Even if in the present case only a single-phase AC voltage P However, the principle of the invention is equally applicable to multi-phase AC voltages, as with respect to 1 explained, analogously applicable.

The charging device 10 includes one with the charging station 14 electrically coupled and the AC voltage P rectifying bridge rectifier 16 , which has a DC voltage connection 18 having, which with a DC voltage intermediate circuit 20 of the electrical system 12 is electrically coupled.

For this purpose, the charging device includes 10 a DC-DC converter 22 that with a first connection 24 with the DC voltage connection 18 and with a second connection 26 with the DC intermediate circuit 20 of the electrical system 12 is electrically coupled. The DC-DC converter 22 is formed, electrical potentials 28 . 30 one at the second port 26 for the DC intermediate circuit 20 provided DC link voltage 32 in relation to the given earth potential 34 to set to predetermined, substantially constant, values. This allows the DC-DC converter 22 achieve that the rectified electrical potentials 28 . 30 despite galvanic coupling no longer opposite the earth potential 34 need to fluctuate, as it is based on 6 has been explained. Despite bridge rectification is possible by the invention, with respect to the ground potential 34 essentially constant electrical potentials 28 . 30 adjust. The problem explained with reference to the state of the art can thereby be considerably reduced.

How out 7 is apparent, are the first and the second port 24 . 26 of the DC-DC converter 22 galvanically coupled. An elaborate electrical isolation as in the DC / DC converter 58 can be saved.

Furthermore, it is off 7 it can be seen that the DC-DC converter 22 is modular and in the present case two converter modules 36 . 38 having. Each of the converter modules 36 . 38 is formed, each associated with the electrical potentials 28 . 30 adjust. This gives the possibility of electrical potentials 28 . 30 symmetrical to the electrical reference potential 34 adjust. However, this symmetry does not necessarily have to be complied with, especially if there is an insulation fault that can lead to a leakage current. In this case, the potential affected by the insulation fault can be shifted so that an electric voltage of the affected one of the potentials 28 . 30 as small as possible in relation to the earth potential 34 is, so that a leakage current due to the insulation error is minimized. Thereby, the above-described harmful effects of the leakage current, in particular if it is a direct current, can be considerably reduced, if not completely suppressed. Despite galvanic coupling in the area of the charging device 10 a much higher security can be achieved with considerably less effort compared to the prior art.

In addition, the charging device includes 10 also a power factor unit 40 for adjusting a power factor with respect to the charging station 14 serves. The power factor unit 40 may reason to like 1 be described described.

To the electrical potentials 28 . 30 in the desired manner, each of the converter modules 36 . 38 adjusting one of the two potentials 28 . 30 assigned. Thus it can be provided that one of the two converter modules 36 . 38 the task is to rectify the AC voltage P the basis of 6 explained negative half waves of the minus potential 30 to correct based on the ground potential 34. It should be noted that to eliminate the negative half-waves with respect to the ground potential 34 at least one choke or a capacitor must be looped, which is operated by means of a clocking switching element, such as a semiconductor switch such as a transistor or the like. Thus, the minus potential 30 based on the earth potential 34 again at a temporally substantially constant value be stabilized. Preferably, the voltage value can be adjusted so that it is the negative half output voltage or intermediate circuit voltage 32 corresponds to, for example, Y capacitors, which are also connected to the DC link 20 , and at its potential 28 . 30 , can be connected, can be operated balanced. As a result, the electric energy stored in these Y capacitors can be reduced, whereby a touch current can be reduced. Because after such a voltage conversion, the DC link voltage 32 not constant with respect to the earth potential 34 would be, but fluctuations corresponding to the negative halfwaves, as based on 6 This could be explained by the second converter module 38 be compensated. The converter module 38 allows the DC link voltage 32 to one in relation to the earth potential 34 to set essentially constant value. A corresponding schematic diagram is shown in FIG 16 shown.

The 12 to 15 show suitable schematic diagram representations, which for the realization of the converter modules 36 . 38 can serve. 12 shows a conventional buck converter for a unidirectional conversion without galvanic isolation. In general, galvanically coupled transducer types are shown so that the plus path is set by a clocking switching element and an energy storage, such as a coil and / or a capacitor, and the negative path is continuous. Such an energy converter can be used for the converter modules 36 , 38 are not used directly, but should be adjusted accordingly that the plus path is continuous and the clocking switching element and the energy storage are located in the minus path.

In this sense shows 12 a conventional buck converter for use in the converter modules 36 . 38 according to 13 is to be modified. The same applies to the conventional boost converter according to 14 which is for use with a converter module 36 . 38 according to the invention accordingly 15 is to be modified.

The 8th to 11 illustrate the effect of the invention by means of schematic diagrams. In all diagrams of the 8th to 11 is the abscissa of time and the ordinate of a respective voltage U ₁ or U ₂ assigned in volts. The voltage U ₁ always refers to a plus potential in relation to the earth potential 34 whereas the tension U ₂ on an electrical voltage between the negative potential and the ground potential 34 refers. In the Fign. each two associated diagrams are shown arranged one above the other. In the upper part of the diagrams is the electrical voltage U ₁ and in the lower of the two diagrams the associated electrical voltage U ₂ represented by respective graphs.

8th shows in an upper schematic diagram by means of a graph 62 the voltage curve immediately after the rectification, namely at the positive potential. By means of a graph 64, the lower diagram shows the corresponding voltage curve for the voltage U ₂ , in terms of the corresponding negative potential.

After performing the power factor correction by the power factor unit 40 the voltage curves change as shown by the diagrams of 9 is represented by the graphs 66 and 68. 10 shows in a further step the effect of the first converter module 36 in which the negative potential is stabilized relative to the ground potential 34. This can be shown with reference to the diagrams shown above, wherein by means of a graph 70, the corresponding positive potential is shown, which is substantially opposite to in 9 the voltage curve shown is unchanged, whereas the negative potential according to the lower diagram can be seen to be substantially constant on the basis of the graph 72.

In order to reduce the fluctuation of the positive potential according to the graph 70 as well, the second converter module is 38 intended. By means of the second converter module 38 can also be the plus potential compared to the earth potential 34 be stabilized, as can be seen from the upper diagram of the 11 from the voltage graph 74 U ₁ is apparent. By means of the graph 76 in the lower of the two diagrams it can be seen that the voltage U ₂ essentially not changed. At the second connection 26 is thus a DC link voltage 32 available, which is opposite to the earth potential 34 is kept substantially constant. This constancy is achieved, although no galvanic isolation is provided.

• - höherer Wirkungsgrad
• - kleinere Bauform, woraus sich eine höhere Leistungsdichte ergeben kann
• - Kostenvorteile, weil weniger Bauteile benötigt werden gegenüber galvanisch getrennten Ladegeräten
• - eine Stabilisierung der elektrischen Potentiale auf der Gleichspannungsseite kann erreicht werden, insbesondere eine Symmetrierung bezüglich eines elektrischen Bezugspotentials, beispielsweise dem Erdpotential 34, an einer Ausgangsseite des galvanisch gekoppelten Ladegeräts. Dadurch kann auch eine gesamte elektrische Energie, die in Y-Kondensatoren gespeichert ist, reduziert werden.
• - Durch die Wandlermodule 36, 38 können Überspannungen aus der Ladestation 14 gedämpft beziehungsweise reduziert werden.

The invention, which suggests a change from a galvanically isolated charger to a galvanically coupled charger, provides the following advantages:

• - higher efficiency
• - smaller design, which may result in a higher power density
• - Cost advantages, because fewer components are required compared to galvanically isolated chargers
• a stabilization of the electrical potentials on the DC voltage side can be achieved, in particular a balancing with respect to an electrical reference potential, for example, the earth potential 34 , on an output side of the galvanic charger. As a result, all electrical energy stored in Y capacitors can also be reduced.
• - Through the converter modules 36 . 38 Surges can be damped or reduced from the charging station 14.

In principle, the second converter module is not absolutely necessary for the invention. The basic function can only be done with the converter module 36 already reached. The output voltage would then possibly not a constant DC voltage.

The exemplary embodiments serve exclusively to explain the invention and are not intended to limit this.

LIST OF REFERENCE NUMBERS

10

loader

12

board network

14

charging station

16

Bridge rectifier

18

DC voltage connection

20

Dc link

22

DC converter

24

first connection

26

second connection

28

Plus potential

30

Negative potential

32

Intermediate circuit voltage

34

ground

36

first converter module

38

second converter module

40

Power factor unit

50

loader

52

charging station

54

Rectifier unit

56

capacitor

58

DC / DC converter

60

vehicle battery

62 to 78

graph

L ₁ , L ₂ , L ₃

phase connection

P

phase connection

N

zero connection

U ₁

tension

U ₂

tension

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 2010/0076636 A1 [0005]

Claims (7)

Energy coupling device (10) for electrically coupling an on-board network (12) of a motor vehicle with a charging station (14) providing an electrical alternating voltage outside the vehicle, with a bridge rectifier (16) which can be electrically coupled to the charging station (14) and rectifies the AC voltage, which has a DC voltage connection (16). 18), which is electrically coupled to a DC voltage intermediate circuit (20) of the electrical system (12), characterized by a DC-DC converter (22) having a first terminal (24) with the DC voltage terminal (18) and with a second terminal (26) is electrically coupled to the DC intermediate circuit (20) of the electrical system (12), wherein the DC-DC converter (22) is formed, electrical potentials (28, 30) at the second terminal (26) for the DC intermediate circuit (20) provided DC link voltage (32) in Reference to a predeterminable electrical reference potential (34) to set to predetermined, substantially constant values. Energy coupling device according to Claim 1 , characterized in that the first and the second terminal (24, 26) of the DC-DC converter (22) are galvanically coupled. Energy coupling device according to Claim 1 or 2 , characterized in that the DC-DC converter (22) is modular and has at least two converter modules (36, 38), wherein each of the converter modules (36, 38) is adapted to set a respectively associated one of the electrical potentials (28, 30). Energy coupling device according to one of the preceding claims, characterized in that the DC-DC converter (22) is designed to adjust the electrical potentials (28, 30) symmetrically to the electrical reference potential (34). Energy coupling device according to one of the preceding claims, characterized in that a power factor unit (40) for setting a power factor with respect to the charging station (14). Energy coupling device according to Claim 5 , characterized in that the power factor unit (40) and at least one of the converter modules (36, 38) are integrally formed. Method for electrically coupling a vehicle electrical system (12) of a motor vehicle with a charging station (14) providing an electrical alternating voltage in which an AC voltage of the charging station (14) can be electrically coupled by means of a bridge rectifier (16) electrically coupled to the charging station (14) and rectifying the AC voltage ) is rectified and is provided at a DC voltage connection (18) electrically coupled to a DC intermediate circuit (20) of the electrical system (12), characterized in that the bridge rectifier (18) is connected to the DC intermediate circuit (20) of the vehicle electrical system (12) by means of a DC voltage converter (22) is electrically coupled, wherein the DC-DC converter (22) electrical potentials (28, 30) provided for the DC intermediate circuit (20) DC link voltage (32) with respect to a predetermined electrical reference potential (34) to predetermined, substantially constant values established.

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