DE102024001850A1 - Device and method for discharging a high-voltage electrical system of an electrically operated vehicle - Google Patents

Abstract

The invention relates to a device (100) for discharging a high-voltage electrical system (10) of an electrically operable vehicle, wherein the high-voltage electrical system (10) is electrically connected to a high-voltage battery (12) via at least one contactor (14) and has a first DC/DC converter (16). A second, bidirectional DC/DC converter (18) is electrically connected to the high-voltage battery (12). The two DC/DC converters (16, 18) are electrically coupled to one another via at least one first low-voltage electrical system (20).The invention further relates to a method for discharging a high-voltage electrical system (10) of an electrically operable vehicle using a device (100).

Description

The invention relates to a device for discharging a high-voltage electrical system of an electrically operated vehicle and to a method for discharging a high-voltage electrical system of an electrically operated vehicle using a device.

Active discharge of a high-voltage electrical system is well known. This method is used to discharge the high-voltage electrical system decentrally through each individual high-voltage component after opening high-voltage contactors. In this process, a DC link capacitor in each component is discharged directly by closing a switch via a discharge resistor.

The energy is converted into heat and cannot be reused, reducing the vehicle's range. A typical asymptotic discharge curve through an ohmic resistor results in a long discharge time, especially if a particularly low voltage is to be achieved.

Furthermore, intermediate circuit discharge using a DC/DC converter is known in the prior art. After the high-voltage contactors are opened, the energy from the high-voltage intermediate circuit is transferred to a low-voltage battery.

This requires a low-voltage battery, whose charge level is important, as the low-voltage battery must not be too full to absorb the electrical energy during discharging. The discharge rate depends on the low-voltage battery's performance. This is severely limited in cold conditions or with advanced aging, for example, which in turn results in a longer discharge time.

The DE 10 2017 209 105 A1 For example, describes a device for discharging a high-voltage intermediate circuit of a vehicle. The high-voltage intermediate circuit comprises an intermediate circuit capacitor and a step-down converter, which converts a high-voltage voltage of the high-voltage intermediate circuit into a low-voltage voltage. The device comprises a low-voltage discharge circuit, which is electrically connected to the step-down converter on the low-voltage side. The device further comprises means configured to switch on the low-voltage discharge circuit in response to a discharge signal.

An object of the invention is to provide an efficient device for discharging a high-voltage electrical system of an electrically operated vehicle.

A further object is to provide a method for discharging a high-voltage electrical system of an electrically operated vehicle using such an efficient device.

The above-mentioned objects are solved by the features of the independent claims.

Advantageous embodiments and advantages of the invention emerge from the further claims, the description and the drawing.

According to one aspect of the invention, a device for discharging a high-voltage electrical system of an electrically operated vehicle is proposed. The high-voltage electrical system is electrically connected to a high-voltage battery via at least one contactor and has a first DC/DC converter. A second, bidirectional DC/DC converter is electrically connected to the high-voltage battery. The two DC/DC converters are electrically coupled to one another via at least one first low-voltage electrical system.

The proposed device comprises the first DC/DC converter, which is located on the high-voltage vehicle electrical system side, and the second DC/DC converter connected to the high-voltage battery. The second DC/DC converter can be electrically connected to the high-voltage battery directly or via a fuse element. However, the second DC/DC converter is not connected to the high-voltage vehicle electrical system. The two DC/DC converters are electrically connected to each other on their low-voltage sides.

The device makes it possible to actively discharge the high-voltage vehicle electrical system when the high-voltage contactors are open, not via a consumer or resistor, but rather to use the first DC/DC converter in the high-voltage vehicle electrical system to feed the energy into the high-voltage battery via a second DC/DC converter coupled on the low-voltage side.

The high-voltage contactors can be designed as two separate contactors. However, there can also be one contactor that switches both poles. A single contactor on just one pole, for example, the positive pole of the high-voltage battery, is also conceivable.

The first DC/DC converter is located in the high-voltage vehicle electrical system, which is separated from the high-voltage battery and thus from the high-voltage supply by opening at least one high-voltage contactor. The second DC/DC converter, designed bidirectionally, is connected directly to the high-voltage battery and, for example, via a coupling element to the first DC/DC converter. This allows The second DC/DC converter can permanently feed energy from the low-voltage range into the high-voltage battery, for example if this energy comes from the high-voltage vehicle electrical system via the first DC/DC converter.

For discharging, at least one of the high-voltage contactors is opened and the low-voltage coupling element is closed. The first DC/DC converter feeds energy from the high-voltage intermediate circuits into the low-voltage electrical system. The second DC/DC converter converts the energy to the high-voltage side, allowing the energy from the low-voltage electrical system to be fed into the high-voltage battery.

The active discharge can be terminated if the high-voltage vehicle electrical system voltage falls below a defined limit, for example below a contact protection low voltage or below a pre-charging limit, in order to ensure re-charging as quickly as possible.

Advantageously, no low-voltage battery is required to discharge the high-voltage electrical system. The discharge time is independent of the low-voltage battery. This allows for increased discharge speed, especially at low outside temperatures.

According to an advantageous embodiment of the device, the two DC/DC converters in the at least one first low-voltage vehicle electrical system can be electrically coupled via an electrical coupling element. This allows the electrical energy to be transferred directly from the low-voltage side of the first DC/DC converter to the low-voltage side of the second DC/DC converter, so that the energy can be converted back to the high-voltage side by the second DC/DC converter and fed into the high-voltage battery. Alternatively, the two DC/DC converters on the low-voltage side can also be permanently electrically coupled to one another.

If two low-voltage electrical systems are present, the two low-voltage electrical systems are coupled by the coupling element.

According to an advantageous embodiment of the device, the second DC/DC converter can be electrically connected to the high-voltage battery via a protection element. Advantageously, the protection element can be integrated into the second DC/DC converter.

According to an advantageous embodiment of the device, the second DC/DC converter can be electrically coupled to a second low-voltage vehicle electrical system.

According to an advantageous embodiment of the device, the first low-voltage electrical system and the second low-voltage electrical system can be electrically coupled via the electrical coupling element. The optional second low-voltage electrical system can advantageously be designed as a redundant low-voltage electrical system and be provided, for example, to supply safety-critical consumers.

According to an advantageous embodiment of the device, the at least one first low-voltage electrical system can have at least one low-voltage battery or be electrically coupled to at least one low-voltage battery. The low-voltage battery can advantageously be used to supply low-voltage consumers, in particular, for example, safety-critical consumers.

According to a further aspect of the invention, a method for discharging a high-voltage electrical system of an electrically operable vehicle is proposed using a device, at least comprising opening at least one contactor between a high-voltage battery and the high-voltage electrical system; feeding electrical energy from the high-voltage electrical system via a first DC/DC converter into at least one first low-voltage electrical system; feeding the electrical energy from the at least one first low-voltage electrical system into the high-voltage battery via a second, bidirectional, DC/DC converter.

With the proposed method, it is possible to actively discharge the high-voltage electrical system when the high-voltage contactors are open, not via a consumer or resistor, but to use the first DC/DC converter in the high-voltage electrical system to feed the energy into the high-voltage battery via a second DC/DC converter coupled on the low-voltage side.

The first DC/DC converter is located in the high-voltage electrical system, which is disconnected from the high-voltage battery and thus from the high-voltage supply by opening at least one high-voltage contactor. The second DC/DC converter, designed bidirectionally, is connected directly to the high-voltage battery and, for example, via a coupling element, to the first DC/DC converter. This allows the second DC/DC converter to continuously feed energy from the low-voltage range into the high-voltage battery, for example, if this energy originates from the high-voltage electrical system via the first DC/DC converter.

For discharging, at least one high-voltage contactor is opened and the low-voltage coupling element is closed. The first DC/DC converter feeds energy from the high-voltage intermediate circuits into the low-voltage vehicle electrical system. The second DC/DC converter converts the energy to the high-voltage side so that the energy from the low-voltage electrical system can be fed into the high-voltage battery.

The active discharge can be terminated if the high-voltage vehicle electrical system voltage falls below a defined limit, for example below a contact protection low voltage or below a pre-charging limit.

Advantageously, no low-voltage battery is required to discharge the high-voltage electrical system. The pre-charging time is independent of the low-voltage battery. This allows for increased pre-charging performance, especially at low outside temperatures.

According to an advantageous embodiment of the method, an electrical coupling element can be connected between the two DC/DC converters before the electrical energy is fed into the at least one first low-voltage vehicle electrical system. This allows the electrical energy to be transferred directly from the low-voltage side of the first DC/DC converter to the low-voltage side of the second DC/DC converter, so that the energy can be converted back to the high-voltage side by the second DC/DC converter and fed into the high-voltage battery.

According to an advantageous embodiment of the method, the discharging of the high-voltage electrical system can be terminated when the electrical voltage of the high-voltage electrical system falls below a predetermined limit. In particular, the predetermined limit can be a touch protection extra-low voltage or a pre-charging limit. This allows the system's safety limits to be adequately maintained.

According to an advantageous embodiment of the method, a second low-voltage electrical system can be supplied directly from the high-voltage battery via the second DC/DC converter. In particular, safety-critical low-voltage consumers in the second low-voltage electrical system can be supplied directly from the high-voltage battery via the second DC/DC converter. The optional second low-voltage electrical system can advantageously be designed as a redundant low-voltage electrical system and, for example, be provided to supply safety-critical consumers.

Further advantages will become apparent from the following description of the drawings. The drawings illustrate an exemplary embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will expediently consider the features individually and combine them into further meaningful combinations.

• 1 eine Systemübersicht einer Vorrichtung zum Entladen eines Hochvolt-Bordnetzes eines elektrisch betreibbaren Fahrzeugs nach einem Ausführungsbeispiel der Erfindung;
• 2 eine Systemübersicht einer Vorrichtung zum Entladen eines Hochvolt-Bordnetzes eines elektrisch betreibbaren Fahrzeugs nach einem weiteren Ausführungsbeispiel der Erfindung; und
• 3 eine schematische Darstellung eines Verfahrens zum Entladen eines Hochvolt-Bordnetzes eines elektrisch betreibbaren Fahrzeugs mit einer Vorrichtung nach einem Ausführungsbeispiel der Erfindung.

Showing:

• 1 a system overview of a device for discharging a high-voltage electrical system of an electrically operated vehicle according to an embodiment of the invention;
• 2 a system overview of a device for discharging a high-voltage electrical system of an electrically operated vehicle according to a further embodiment of the invention; and
• 3 a schematic representation of a method for discharging a high-voltage electrical system of an electrically operated vehicle with a device according to an embodiment of the invention.

In the figures, identical or similar components are designated by the same reference numerals. The figures are merely examples and are not to be construed as limiting.

1 shows a system overview of a device 100 for discharging a high-voltage electrical system 10 of an electrically operated vehicle according to an embodiment of the invention.

The high-voltage electrical system 10, which is shown only symbolically, is electrically connected to a high-voltage battery 12 via at least one contactor 14, which switches in both poles, or via two contactors 14. Furthermore, the high-voltage electrical system 10 is coupled to a first DC/DC converter 16. A second, bidirectional DC/DC converter 18 is directly electrically connected to the high-voltage battery 12. The two DC/DC converters 16, 18 are electrically coupled to one another via at least one first low-voltage electrical system 20.

The second DC/DC converter 18 can also be directly electrically connected to the high-voltage battery 12 via a fuse element, which can be integrated, for example, in the second DC/DC converter 18.

In the 1 In the illustrated embodiment, the two DC/DC converters 16, 18 in the first low-voltage electrical system 20 are electrically coupled via an electrical coupling element 22. The low-voltage electrical system 20 further includes an optional low-voltage consumer 24.

At least the second DC/DC converter 18 is bidirectional and can convert electrical energy from the high-voltage battery 12 and feed it into the low-voltage electrical system 20, as well as reverse electrical energy from the low dervolt electrical system 20 to the high-voltage side and feed it into the high-voltage battery 12.

To discharge the high-voltage electrical system 10, the two contactors 14 between the high-voltage battery 12 and the high-voltage electrical system 10 are opened.

The electrical energy from the high-voltage electrical system 10 is converted into the first low-voltage electrical system 20 via the first DC/DC converter 16.

Before the electrical energy is fed into the at least one first low-voltage vehicle electrical system 20, the electrical coupling element 22 between the two DC/DC converters 16, 18 is closed.

Furthermore, the converted electrical energy from the first low-voltage electrical system 20 is fed into the high-voltage battery 12 via the second DC/DC converter 18.

The discharging of the high-voltage electrical system 10 is terminated when the electrical voltage of the high-voltage electrical system 10 falls below a predefined limit. In particular, the predefined limit can be a touch protection extra-low voltage or a precharging limit to ensure recharging as quickly as possible.

2 shows a system overview of a device 100 according to a further embodiment of the invention.

In the 2 In the exemplary embodiment shown, the first low-voltage electrical system 20 has a low-voltage battery 28.

A second low-voltage electrical system 30 is fed directly from the high-voltage battery 12 via the second DC/DC converter 18.

The second low-voltage electrical system 30 also has an optional low-voltage consumer. One or more consumers 26 can be electrically connected to both low-voltage electrical systems 20, 30. A further consumer 26 can, in particular, be a safety-critical low-voltage consumer 26, which can be supplied directly from the high-voltage battery 12 in the second low-voltage electrical system 30 via the second DC/DC converter 18.

The first low-voltage electrical system 20 and the second low-voltage electrical system 30 are electrically coupled via the electrical coupling element 22, so that electrical energy from the high-voltage electrical system 10 can be fed into the first low-voltage electrical system 20 via the first DC/DC converter 16, from there transferred into the second low-voltage electrical system 30 via the electrical coupling element 22 and then fed back into the high-voltage battery 12 via the second DC/DC converter 18.

3 shows a schematic representation of a method for discharging a high-voltage electrical system 10 of an electrically operable vehicle using a device 100 according to an embodiment of the invention. The electrical energy flow is represented by dotted arrows.

As a starting point before discharging, the high-voltage electrical system 10 is charged. The high-voltage contactors 14 are closed. For discharging, the intermediate circuit capacitances of the high-voltage components in the high-voltage electrical system 10 must be discharged. For example, these can be the intermediate circuit capacitances of the inverter, an air conditioning compressor, an onboard charger, or a heater.

Before discharging, the high-voltage contactors 14 are opened. The low-voltage coupling element 22 is closed.

The first DC/DC converter 16 feeds energy from the high-voltage intermediate circuits of the components of the high-voltage electrical system 10 into the low-voltage electrical system 20. The energy is transferred to the second DC/DC converter 18 via the electrical coupling element 22. The second DC/DC converter 18 converts the energy from the low-voltage electrical system 20 back to the high-voltage side so that the energy can be fed into the high-voltage battery 12.

The discharge process can be terminated if the high-voltage vehicle electrical system voltage falls below a defined limit, for example if the high-voltage vehicle electrical system voltage falls below a contact protection extra-low voltage or below a pre-charging limit.

List of reference symbols

10

High-voltage electrical system

12

High-voltage battery

14

High-voltage contactor

16

first DC/DC converter

18

second DC/DC converter

20

first low-voltage electrical system

22

electrical coupling element

24

Low-voltage consumers

26

safety-critical consumer

28

Low-voltage battery

30

second low-voltage electrical system

100

Energy storage system

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

• DE 10 2017 209 105 A1 [0006]

Claims (10)

Device (100) for discharging a high-voltage electrical system (10) of an electrically operated vehicle, wherein the high-voltage electrical system (10) is electrically connected to a high-voltage battery (12) via at least one contactor (14) and has a first DC/DC converter (16), wherein a second, bidirectional, DC/DC converter (18) is electrically connected to the high-voltage battery (12) and the two DC/DC converters (16, 18) are electrically coupled to one another via at least one first low-voltage electrical system (20). Device according to Claim 1 , wherein the two DC/DC converters (16, 18) in the at least one first low-voltage vehicle electrical system (20) are electrically coupled via an electrical coupling element (22). Device according to Claim 1 or 2 , wherein the second DC/DC converter (18) is electrically connected to the high-voltage battery (12) via a fuse element. Device according to one of the preceding claims, wherein the second DC/DC converter (18) is electrically coupled to a second low-voltage vehicle electrical system (30). Device according to one of the Claims 2 until 4 , wherein the first low-voltage electrical system (20) and the second low-voltage electrical system (30) are electrically coupled via the electrical coupling element (22). Device according to one of the preceding claims, wherein the at least one first low-voltage vehicle electrical system (20) has at least one low-voltage battery (28) or is electrically coupled to at least one low-voltage battery (28). A method for discharging a high-voltage electrical system (10) of an electrically operable vehicle with a device (100) according to one of the preceding claims, at least comprising: Opening at least one contactor (14) between a high-voltage battery (12) and the high-voltage electrical system (10); Feeding electrical energy from the high-voltage electrical system (10) via a first DC/DC converter (16) into at least one first low-voltage electrical system (20); Feeding the electrical energy from the at least one first low-voltage electrical system (20) into the high-voltage battery (12) via a second, bidirectional DC/DC converter (18). Procedure according to Claim 7 , wherein an electrical coupling element (22) is closed between the two DC/DC converters (16, 18) before the electrical energy is fed into the at least one first low-voltage vehicle electrical system (20). Procedure according to Claim 7 or 8 , wherein the discharging of the high-voltage vehicle electrical system (10) is terminated when an electrical voltage of the high-voltage vehicle electrical system (10) falls below a predetermined limit value, in particular wherein the predetermined limit value is a contact protection extra-low voltage or a pre-charging limit value. Method according to one of the Claims 7 until 9 , wherein a second low-voltage vehicle electrical system (30) is fed directly from the high-voltage battery (12) via the second DC/DC converter (18), in particular wherein safety-critical low-voltage consumers (26) in the second low-voltage vehicle electrical system (30) are supplied directly from the high-voltage battery (12) via the second DC/DC converter (18).

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