DE102019214870A1 - Circuit arrangement for a motor vehicle and method for stabilizing a direct voltage of a high-voltage direct voltage intermediate circuit in a motor vehicle - Google Patents

Abstract

The invention relates to a circuit arrangement (1) for a motor vehicle, the motor vehicle being able to be supplied with direct current at least temporarily via an overhead line (20), comprising a high-voltage battery (4) for providing electrical energy, a high-voltage DC voltage intermediate circuit (5 ), which can be coupled to an overhead line (20) carrying direct current, and a DC voltage converter (7) between the high-voltage DC voltage intermediate circuit (5) and the high-voltage battery (4), the DC voltage converter (7) being designed in this way, a DC voltage (UE) of the high-voltage direct voltage intermediate circuit (5) in the event of a voltage drop caused by a loss of contact between the high-voltage direct voltage intermediate circuit (5) and the overhead line (20) by transferring energy from the high-voltage battery (4) and / or a direct voltage (UE ) in the event of a loss of contact between the high-voltage DC intermediate circuit and to reduce the voltage rise caused by the overhead line (20) by increasing an energy transfer into the high-voltage battery (4). The invention also relates to a method for stabilizing a direct voltage (UE) of a high-voltage direct voltage intermediate circuit (5) in a motor vehicle.

Description

The invention relates to a circuit arrangement for a motor vehicle and a method for stabilizing a direct voltage of a high-voltage direct voltage intermediate circuit in a motor vehicle. The invention also relates to a motor vehicle.

In the field of electromobility, concepts for electrifying the drive train of commercial vehicles are increasingly being developed. However, an insufficient energy density of the energy storage devices used is a problem here. One solution to the problem is the provision of electrical energy from the outside via an overhead line. The utility vehicle can then be operated via the overhead line and / or the energy store can be charged while driving. If an electrical connection is established between a current collector of the motor vehicle and the overhead line, then there may be brief loss of contact between the current collector and the overhead line due to uneven road surfaces and vibrations. On one side of the motor vehicle, such a brief loss of contact leads to a brief voltage fluctuation.

It is known to use input filters to mitigate voltage drops caused by loss of contact by smoothing the voltage over time. These input filters are usually designed as a choke inductance or as an LC filter.

The invention is based on the object of creating a circuit arrangement for a motor vehicle and a method for stabilizing a direct voltage of a high-voltage direct voltage intermediate circuit in a motor vehicle, with which it is possible to respond better to a voltage fluctuation.

According to the invention, the object is achieved by a circuit arrangement with the features of claim 1 and a method with the features of claim 7. Advantageous embodiments of the invention emerge from the subclaims.

In particular, a circuit arrangement is created for a motor vehicle, the motor vehicle being able to be supplied with direct current at least temporarily via an overhead line, comprising a high-voltage battery for providing electrical energy, a high-voltage direct voltage intermediate circuit which can be coupled to an overhead contact line carrying direct current, and a DC voltage converter between the high-voltage DC voltage intermediate circuit and the high-voltage battery, the DC voltage converter being designed in such a way that a direct voltage of the high-voltage DC voltage intermediate circuit is supplied by energy transfer from the high-voltage battery in the event of a voltage drop caused by a loss of contact between the high-voltage DC voltage intermediate circuit and the overhead line and / or a DC voltage of the high-voltage DC voltage intermediate circuit in the event of a loss of contact between the high-voltage DC voltage intermediate circuit and the overhead line to reduce the voltage increase caused by increasing an energy transfer into the high-voltage battery.

Furthermore, a method for stabilizing a direct voltage of a high-voltage direct voltage intermediate circuit in a motor vehicle is provided, comprising the steps of: providing electrical energy by means of a high-voltage battery, providing a high-voltage direct voltage intermediate circuit which can be coupled to an overhead contact line carrying direct current, and supporting a DC voltage of the high-voltage DC voltage intermediate circuit in the event of a voltage drop caused by a loss of contact between the high-voltage DC voltage intermediate circuit and the overhead line due to energy transfer from the high-voltage battery by means of a DC voltage converter and / or reducing a DC voltage of the high-voltage DC voltage intermediate circuit in the event of a loss of contact between the High-voltage direct voltage intermediate circuit and the overhead line caused voltage increase by increasing an energy transfer in the high-voltage battery by means of the DC voltage converter.

The circuit arrangement and the method make it possible to actively compensate for a voltage drop and / or a voltage increase and thereby to hold or stabilize a direct voltage of the high-voltage direct voltage intermediate circuit at a predetermined voltage value. This is done when power is taken from the overhead line by compensating for the voltage drop caused by a loss of contact between the high-voltage DC link or a pantograph connected to it and the overhead line using a DC voltage converter (also known as a DC / DC converter). For this purpose, the DC voltage converter generates, on the side facing the high-voltage DC voltage intermediate circuit, in particular a backup voltage that keeps a direct voltage constant in the high-voltage DC voltage intermediate circuit, and for this purpose reverses a power flow from the high-voltage battery in the direction of the high-voltage DC voltage intermediate circuit. If, however, electrical power is fed into the overhead line system, for example by means of a generator operating electrical machine, a voltage increase caused by the loss of contact in the DC voltage intermediate circuit is also compensated by means of the DC voltage converter. For this purpose, the DC voltage converter reduces the DC voltage in the DC voltage intermediate circuit on the side facing the high-voltage DC voltage intermediate circuit, in that an energy transfer into the high-voltage battery is increased.

One advantage of the invention is that active compensation of a voltage dip and / or a voltage rise is made possible, so that the voltage dip and / or the voltage rise can be fully compensated. In contrast, complete compensation is not possible with circuit arrangements from the prior art that are based on input filters and choke inductances, that is to say purely passive components. With the circuit arrangement and the method, it is particularly possible to provide a supported or constant and stabilized voltage, for example to operate an electrical machine and other high-voltage consumers, and thereby maintain normal operation even in the event of a loss of contact.

Another advantage of the invention is that, due to the active compensation or stabilization, an input filter can be completely dispensed with or at least components of the input filter or a choke inductance can be dimensioned smaller. This can save costs.

The circuit arrangement, in particular the DC voltage converter, is controlled or regulated by means of a control device. The control device can be designed as a combination of hardware and software, for example as program code that is executed on a microcontroller or microprocessor.

An electrical machine of the motor vehicle or a drive converter of the electrical machine are in particular connected to the high-voltage DC voltage intermediate circuit and can be supplied with electrical energy both from the overhead line and from the high-voltage battery. The electrical machine can also be operated as a generator in particular.

In one embodiment it is provided that the DC-DC converter is designed as a bidirectional DC-DC converter, the DC-DC converter also being designed to convert a DC voltage provided by the overhead line to a charging voltage of the high-voltage battery if required. In a first operating state, the DC voltage converter can convert a voltage of the overhead line to a charging voltage of the high-voltage battery, so that the high-voltage battery can be charged via the overhead line. In a second operating state, a power flow can be reversed and the DC / DC converter is used to support the DC voltage in the high-voltage DC voltage intermediate circuit in the event of a voltage drop. The first operating state is also used to reduce the DC voltage in the DC voltage intermediate circuit. A bidirectional design means that overall components can be saved, since the DC / DC converter can be operated in two directions.

In one embodiment it is provided that the circuit arrangement has at least one voltage sensor arranged on the high-voltage DC voltage intermediate circuit, the at least one voltage sensor having a sampling frequency of at least 100 kHz, and the DC voltage converter being designed to support and / or reduce the DC voltage To regulate based on acquired sensor data of the at least one voltage sensor. With a sampling frequency of at least 100 kHz, a voltage drop or a voltage rise and its course can be detected with a corresponding resolution and therefore without a great delay after an occurrence.

In one embodiment it is provided that a voltage regulation of the DC voltage converter has a regulation frequency of at least 10 kHz on a side facing the high-voltage DC voltage intermediate circuit. This enables a quick reaction to a voltage drop or a voltage rise and a rapidly changing voltage in the high-voltage DC voltage intermediate circuit.

Features for the configuration of the method emerge from the description of configurations of the circuit arrangement. The advantages of the method are in each case the same as in the embodiments of the circuit arrangement.

Furthermore, a motor vehicle is created, comprising at least one circuit arrangement according to any one of the described embodiments. In particular, it can be provided that the motor vehicle is a utility vehicle.

• 1 eine schematische Darstellung einer Ausführungsform der Schaltungsanordnung für ein Kraftfahrzeug;
• 2a eine schematische Darstellung eines zeitlichen Verlaufs der Ströme und Spannungen während eines Kontaktverlustes ohne Stützung der Spannung;
• 2b eine schematische Darstellung eines zeitlichen Verlaufs der Ströme und Spannungen während eines Kontaktverlustes mit Stützung der Spannung;
• 2c eine schematische Darstellung von zugehörigen Lastkennlinien und Arbeitspunkten;
• 3a eine schematische Darstellung eines zeitlichen Verlaufs der Ströme und Spannungen während eines Kontaktverlustes ohne Verringern der Spannung (generatorischer Betrieb der elektrischen Maschine);
• 3b eine schematische Darstellung eines zeitlichen Verlaufs der Ströme und Spannungen während eines Kontaktverlustes mit einem Verringern der Spannung (generatorischer Betrieb der elektrischen Maschine);
• 3c eine schematische Darstellung von zugehörigen Lastkennlinien und Arbeitspunkten.

The invention is explained in more detail below on the basis of preferred exemplary embodiments with reference to the figures. Here show:

• 1 a schematic representation of an embodiment of the circuit arrangement for a motor vehicle;
• 2a a schematic representation of a time curve of the currents and voltages during a loss of contact without support of the voltage;
• 2 B a schematic representation of a time curve of the currents and voltages during a loss of contact with support of the voltage;
• 2c a schematic representation of the associated load characteristics and operating points;
• 3a a schematic representation of a time curve of the currents and voltages during a loss of contact without reducing the voltage (generator operation of the electrical machine);
• 3b a schematic representation of a time profile of the currents and voltages during a loss of contact with a reduction in the voltage (generator operation of the electrical machine);
• 3c a schematic representation of the associated load characteristics and operating points.

In 1 is a schematic representation of an embodiment of the circuit arrangement 1 shown for a motor vehicle. The motor vehicle can have an overhead contact line 20th be supplied with electrical energy. This requires an electrical connection between the overhead line 20th and a high-voltage network 3 of the motor vehicle are trained. The circuit arrangement 1 is with a pantograph 2 of the motor vehicle connected.

The circuit arrangement 1 includes a high-voltage battery 4th to provide electrical energy, a high-voltage DC voltage intermediate circuit 5 and a DC / DC converter 7th between the high-voltage DC link 5 and the high-voltage battery 4th . The circuit arrangement 1 , especially the DC-DC converter 7th , is controlled or regulated by means of a control device (not shown).

It is provided in particular that the DC voltage converter 7th as a bidirectional DC voltage converter 17th is formed, wherein the DC voltage converter 7th is also designed such, one of the overhead line 20th Provided DC voltage UF, if required, to a charging voltage of the high-voltage battery 4th to walk.

Via a coupling device 6th the high-voltage DC link 5 with the overhead line 20th be electrically connected.

The motor vehicle also includes an electrical machine 10 that have a drive converter 11 and another coupling device 12 both with the high-voltage battery 4th as well as with the high-voltage DC link 5 can be connected. The further coupling device 12 includes, for example, switching devices 13th , 14th with which the electric machine 10 via the drive inverter 11 with the high-voltage battery 4th or with the high-voltage DC link 5 can be connected. Further electrical high-voltage consumers can also be used 15th with the high-voltage battery 4th be connected.

The pantograph 2 includes a choke inductor 18th , an electrical fuse 19th and a precharge resistor 22nd . The high-voltage battery 4th includes an electrical fuse 8th and an internal switching device 9 to disconnect an electrical connection to the high-voltage network 3 in case of overload.

If there is a loss of contact between the overhead line, for example due to uneven road surfaces or vibrations 20th and sliding contacts 21st of the pantograph 2 , so it comes with a decrease in power from the overhead line 20th to a collapse in tension UP .

This is shown schematically in the 2a shown. The 2a shows a course of currents 30th and tensions 31 over time 32 . It is assumed here over the entire period shown that a power consumption is constant. At a point in time t0, there is a normal operating state and the circuit arrangement 1 is in a first working point 40 . A current flow of a stream IE to the electric machine 10 and a stream ID to the DC / DC converter 7th is such that a power flow to the electrical machine 10 and via the DC / DC converter 7th to the high-voltage battery 4th he follows. The DC / DC converter 7th charges the high-voltage battery 4th .

At a time t1 loss of contact occurs. The loss of contact lasts until the point in time t2 . Such a loss of contact typically lasts for a few milliseconds. In this time between the points in time t1 and t2 there is a collapse in tension UP . Due to the choke inductance 18th ( 1 ) the curve of the voltage dip is smoothed and thereby mitigated so that the stresses UD and UE in the high-voltage DC link 5 although fall off and the circuitry 1 in a second working point 41 is located. However, it is a progression over time 32 smoothed. Due to the assumed constant power consumption, the currents are IE and ID compared to the normal operating state at the first operating point 40 in the time between t1 and t2 greater.

The DC / DC converter 7th supports a DC voltage UE of the high-voltage DC link 5 one by a loss of contact between a pantograph 2 and the overhead line 20th voltage drop caused by energy transfer from the high-voltage battery 4th .

The support of the tension is shown schematically in FIG 2 B shown. The timing of the loss of contact is identical to that in the 2a sequence shown, the same reference numerals denote the same terms and features. To support the DC voltage UE in the high-voltage DC link 5 the DC / DC converter returns 7th between the times t1 and t2 a current direction of the current ID and thereby causes a flow of power from the high-voltage battery 4th into the high-voltage DC link 5 . This is done with the help of voltage regulation on the high-voltage DC voltage intermediate circuit 5 facing side. By changing the current ID become the tensions UE and UD in the high-voltage DC link 5 on the value of the tensions UE , UD raised before loss of contact occurs. The DC / DC converter 7th thus represents a current difference to support the original voltage present at time t0 UE ready.

It can be provided that the circuit arrangement 1 one on the high-voltage DC link 5 arranged voltage sensor 16 having, the voltage sensor 16 has a sampling frequency of at least 100 kHz, and wherein the DC-DC converter 7th supporting the tension based on acquired sensor data from the tension sensor 16 regulates.

It can also be provided that a voltage regulation of the DC voltage converter 7th on one of the high-voltage DC link 5 facing side has a control frequency of at least 10 kHz.

In 2c is a schematic representation of load characteristics 43 , 44 with different working points 40 , 41 , 42 shown. The x-axis 33 denotes a current and the y-axis 34 denotes the voltages UE (= UD ) in the high-voltage DC link 5 . The working points 40 , 41 , 42 are also in the 2a and 2 B shown.

The load characteristics 43 , 44 show the dependence of the voltage UE (= UD ) from the current in the high-voltage DC voltage intermediate circuit assuming constant power consumption. The load curve 43 describes a dependency during a normal operating state in which there is electrical contact between the pantograph 2 and the overhead line 20th consists. The load curve 44 describes, however, a dependency during the loss of contact. It is assumed here that the contact does not break off completely, but rather that an electrical resistance increases. For this reason, the load curve 44 In terms of amount, it has a greater slope than the load curve 43 .

In the normal operating state, the circuit arrangement 1 in the first working point 40 on the characteristic 43 operated. The streams IE and ID add up. If there is a loss of contact, the circuit arrangement is in place 1 without a support of tension UE (= UD ) due to the increased currents IE and ID in the second working point 41 on the characteristic 44 . With a support of tension UE where the electricity ID opposite of the current IE acts, there is the circuit arrangement 1 however, in the third working point 42 , that is, on the same voltage UE like the first working point 40 on the load curve 43 , that is, as in normal operating mode.

The electrical machine is located 10 however in generator mode and electrical power is in the overhead line 20th fed in, there is an increase in voltage UP if there is a loss of contact between the overhead line 20th and sliding contacts 21st of the pantograph 2 comes.

This is shown schematically in the 3a shown. The 3a shows a course of currents 30th and tensions 31 over time 32 . It is assumed here over the entire period shown that a generative output is constant. At a point in time t0, there is a normal operating state and the circuit arrangement 1 is in a first working point 40 . A current flow of a stream IE from the electric machine 10 and a stream ID to the DC / DC converter 7th is such that a power flow from the electrical machine 10 to the overhead line 20th and via the DC / DC converter 7th to the high-voltage battery 4th he follows. The DC / DC converter 7th charges the high-voltage battery 4th .

At a time t1 loss of contact occurs. The loss of contact lasts until the point in time t2 . Such a loss of contact typically lasts for a few milliseconds. In this time between the points in time t1 and t2 there is an increase in tension UP . Due to the choke inductance 18th ( 1 ) the curve of the voltage dip is smoothed and thereby mitigated so that the stresses UD and UE in the high-voltage DC link 5 although increase and the circuit arrangement 1 in a second working point 41 is located. However, it is a progression over time 32 smoothed. Due to the assumed constant generative power, the amounts of the currents decrease IE and ID compared to the normal operating state at the first operating point 40 in the time between t1 and t2 .

The DC / DC converter 7th reduces a DC voltage UE of the high-voltage DC link 5 one by a loss of contact between a pantograph 2 and the overhead line 20th voltage increase caused by increasing energy transfer to the high-voltage battery 4th .

The reduction of the DC voltage is shown schematically in FIG 3b shown. The timing of the loss of contact is identical to that in the 3a sequence shown, the same reference numerals denote the same terms and features. To reduce the DC voltage UE in the high-voltage DC link 5 increases the DC / DC converter 7th between the times t1 and t2 the stream ID and thereby causes an (increased) power flow from the DC voltage intermediate circuit 5 into the high-voltage battery 4th . This is done with the help of voltage regulation on the high-voltage DC voltage intermediate circuit 5 facing side. By changing the current ID become the tensions UE and UD in the high-voltage DC link 5 on the value of the tensions UE , UD before loss of contact occurs. The DC / DC converter 7th thus represents a current difference for setting the original voltage present at time t0 UE ready.

It can be provided that the circuit arrangement 1 one on the high-voltage DC link 5 arranged voltage sensor 16 having, the voltage sensor 16 has a sampling frequency of at least 100 kHz, and wherein the DC-DC converter 7th reducing the tension based on sensed sensor data from the tension sensor 16 regulates.

It can also be provided that a voltage regulation of the DC voltage converter 7th on one of the high-voltage DC link 5 facing side has a control frequency of at least 10 kHz.

In 3c is a schematic representation of load characteristics 43 , 44 with different working points 40 , 41 , 42 shown. The x-axis 33 denotes a current and the y-axis 34 denotes the voltages UE (= UD ) in the high-voltage DC link 5 . The working points 40 , 41 , 42 are also in the 3a and 3b shown.

The load characteristics 43 , 44 show the dependence of the voltage UE (= UD ) from the current in the high-voltage DC link 5 assuming constant generative performance. The load curve 43 describes a dependency during a normal operating state in which there is electrical contact between the pantograph 2 and the overhead line 20th consists. The load curve 44 describes, however, a dependency during the loss of contact. It is assumed here that the contact does not break off completely, but rather that an electrical resistance increases. For this reason, the load curve 44 In terms of amount, it has a greater slope than the load curve 43 .

In the normal operating state, the circuit arrangement 1 in the first working point 40 on the characteristic 43 operated. A stream IE in the high-voltage direct voltage intermediate circuit is generated by the current ID decreased. If there is a loss of contact, the circuit arrangement is in place 1 without lowering the tension UE (= UD ) by the currents reduced in amount IE and ID in the second working point 41 on the characteristic 44 . To decrease the tension UE becomes a stream ID into the DC / DC converter 7th increased, so that an (increased) power flow from the DC voltage intermediate circuit 5 into the high-voltage battery 4th he follows. Assuming the same regenerative power, it increases by reducing the voltage UE correspondingly a stream IE . The circuit arrangement 1 is then in the third working point 42 , that is, on the same voltage UE like the first working point 40 on the load curve 43 , that is, as in normal operating mode.

The advantage of the circuit arrangement 1 and the method is that even in the event of a loss of contact, a supported or constant and stabilized DC voltage UE to operate the electrical machine 10 and other high-voltage consumers 15th in the high-voltage DC link 5 can be provided and normal operation is therefore not interrupted or disturbed even during the loss of contact.

List of reference symbols

1

Circuit arrangement

2

Pantograph

3

High-voltage network

4th

High-voltage battery

5

High-voltage DC link

6th

Coupling device

7th

DC-DC converter

8th

electrical fuse

9

internal switching device

10

electric machine

11

Drive converter

12

further coupling device

13

Switching device

14th

Switching device

15th

High-voltage consumers

16

Voltage sensor

17th

bidirectional DC voltage converter

18th

Choke inductance

19th

electrical fuse

20th

Overhead line

21st

Sliding contact

22nd

Precharge resistor

30th

electricity

31

tension

32

time

33

X axis

34

y-axis

40

first working point

41

second working point

42

third working point

43

Load curve (normal operation)

44

Load curve (support operation)

51

electrical fuse

52

internal switching device

t0-t2

Points in time

UP

Voltage (pantograph)

IP

Electricity (pantograph)

UE

Voltage (intermediate circuit)

IE

Current (intermediate circuit)

UD

Voltage (direct current converter)

ID

Current (direct current converter)

UB

Voltage (high-voltage battery)

IB

Electricity (high-voltage battery)

IE

Current (intermediate circuit)

Claims (10)

Circuit arrangement (1) for a motor vehicle, the motor vehicle being able to be supplied with direct current at least temporarily via an overhead line (20), comprising: a high-voltage battery (4) to provide electrical energy, a high-voltage DC voltage intermediate circuit (5) which can be coupled to an overhead contact line (20) carrying direct current, and a DC voltage converter (7) between the high-voltage DC voltage intermediate circuit (5) and the high-voltage battery (4), wherein the DC voltage converter (7) is designed in such a way that a DC voltage (UE) of the high-voltage DC voltage intermediate circuit (5) in the event of a voltage drop caused by a loss of contact between the high-voltage DC voltage intermediate circuit (5) and the overhead line (20) due to the transfer of energy from the high-voltage battery (4) to support and / or a direct voltage (UE) of the high-voltage direct voltage intermediate circuit (5) in the event of a voltage increase caused by a loss of contact between the high-voltage direct voltage intermediate circuit (5) and the overhead line (20) by increasing an energy transfer into the high-voltage battery (4) decrease. Circuit arrangement (1) according to Claim 1 , characterized in that the DC voltage converter (7) is designed as a bidirectional DC voltage converter (17), wherein the DC voltage converter (7) is also designed in such a way that a DC voltage (UF) provided by the overhead line (20) is converted to a charging voltage of the high-voltage To convert battery (4). Circuit arrangement (2) according to Claim 1 or 2 , characterized by at least one voltage sensor (16) arranged on the high-voltage DC voltage intermediate circuit (5), the at least one voltage sensor (16) having a sampling frequency of at least 100 kHz, and the DC voltage converter (7) being designed to support and / or to regulate reducing the direct voltage (UE) on the basis of detected sensor data of the at least one voltage sensor (16). Circuit arrangement (1) according to one of the preceding claims, characterized in that a voltage control of the DC voltage converter (7) has a control frequency of at least 10 kHz on a side facing the high-voltage DC voltage intermediate circuit (5). Motor vehicle, comprising at least one circuit arrangement (1) according to any one of Claims 1 to 4th . Motor vehicle after Claim 5 , characterized in that the motor vehicle is a utility vehicle. Method for stabilizing a direct voltage (UE) of a high-voltage direct voltage intermediate circuit (5) in a motor vehicle, comprising the steps: Provision of electrical energy by means of a high-voltage battery (4), Providing a high-voltage DC voltage intermediate circuit (5) which can be coupled to an overhead contact line (20) carrying direct current, and Support of a direct voltage (UE) of the high-voltage direct voltage intermediate circuit (5) in the event of a voltage drop caused by a loss of contact between the high-voltage direct voltage intermediate circuit (5) and the overhead line (20) through energy transfer from the high-voltage battery (4) by means of a DC voltage converter (7) and or Reduction of a direct voltage (UE) of the high-voltage direct voltage intermediate circuit (5) in the event of a voltage increase caused by a loss of contact between the high-voltage direct voltage intermediate circuit (5) and the overhead line (20) by increasing an energy transfer into the high-voltage battery (4) by means of the DC voltage converter ( 7). Procedure according to Claim 7 , characterized in that the DC voltage converter (7) is designed as a bidirectional DC voltage converter (17), a DC voltage (UF) provided by the overhead line (20) being converted to a charging voltage of the high-voltage battery (4) if necessary. Procedure according to Claim 7 or 8th , characterized in that a direct voltage (UE) is regulated on the basis of sensor data of at least one voltage sensor (16) arranged on the high-voltage direct voltage intermediate circuit (5), the direct voltage (UE) being detected with a sampling frequency of at least 100 kHz. Method according to one of the Claims 7 to 9 , characterized in that voltage regulation takes place on a side facing the high-voltage DC voltage intermediate circuit (5) with a regulating frequency of at least 10 kHz.

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