Device and method for discharging a high-voltage electrical system of an electrically powered vehicle

Abstract

The invention relates to a device (100) for discharging a high-voltage electrical system (10) of an electrically powered vehicle, wherein the high-voltage electrical system (10) is electrically connected to a high-voltage battery (12) via at least one contactor (14) and comprises 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 each other 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 operated vehicle using a device (100).

Description

[0001] The invention relates to a device for discharging a high-voltage electrical system of an electrically powered vehicle and a method for discharging a high-voltage electrical system of an electrically powered vehicle using a device.

[0002] An active discharge of a high-voltage electrical system is known. This method serves to discharge the high-voltage electrical system decentrally through each individual high-voltage component after high-voltage contactors have been opened. In this process, a DC link capacitor in each component is discharged directly via a discharge resistor by closing a switch.

[0003] The energy is converted into heat and cannot be reused, thus reducing the vehicle's range. A typical asymptotic discharge curve through a resistive load results in a long discharge time, especially when a particularly low voltage is required.

[0004] Furthermore, a DC link discharge using a DC / DC converter is known in the prior art. For this purpose, after the high-voltage contactors are opened, the energy of the high-voltage DC link is transferred to a low-voltage battery.

[0005] This requires a low-voltage battery, the state of charge of which is important, as the low-voltage battery must not be too full in order to be able to absorb electrical energy during discharge. The discharge rate depends on the capacity of the low-voltage battery. This capacity is significantly reduced, for example, in cold weather or with advanced age, which in turn results in a longer discharge time.

[0006] DE 10 2017 209 105 A1 describes, for example, a device for discharging a high-voltage intermediate circuit of a vehicle. The high-voltage intermediate circuit comprises an intermediate circuit capacitor and a buck converter, which converts the high-voltage voltage of the high-voltage intermediate circuit into a low-voltage voltage. The device includes a low-voltage discharge circuit, which is electrically connected to the buck converter on the low-voltage side. Furthermore, the device includes means configured to switch on the low-voltage discharge circuit depending on a discharge signal.

[0007] One objective of the invention is to create an efficient device for discharging a high-voltage electrical system of an electrically powered vehicle.

[0008] Another task is to specify a method for discharging a high-voltage electrical system of an electrically powered vehicle using such an efficient device.

[0009] The aforementioned tasks are solved using the characteristics of independent claims.

[0010] Favorable embodiments and advantages of the invention will become apparent from the further claims, the description and the drawing.

[0011] According to one aspect of the invention, a device for discharging a high-voltage electrical system of an electrically powered vehicle is proposed, wherein the high-voltage electrical system is electrically connected to a high-voltage battery via at least one contactor and comprises 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 each other via at least one first low-voltage electrical system.

[0012] The proposed device comprises a first DC / DC converter, located on the high-voltage electrical system side, and a 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 electrical system. The two DC / DC converters are electrically connected to each other on their low-voltage sides.

[0013] With this device, it is possible to actively discharge the high-voltage electrical system with the high-voltage contactors open, not via a consumer or resistor, but by using 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.

[0014] The high-voltage contactors can be designed as two separate contactors. However, there can also be a single contactor that switches both poles. A single contactor on only one pole, for example the positive terminal of the high-voltage battery, is also conceivable.

[0015] The first DC / DC converter is located in the high-voltage electrical system and is disconnected from the high-voltage battery and thus 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, to the first DC / DC converter via a coupling element. This allows energy to be continuously fed from the low-voltage system into the high-voltage battery via the second DC / DC converter, for example, when this energy originates from the high-voltage electrical system via the first DC / DC converter.

[0016] For discharge, 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, so that energy from the low-voltage electrical system can be fed into the high-voltage battery.

[0017] Active discharge can be terminated when the high-voltage on-board voltage falls below a defined limit, for example below a touch protection extra-low voltage or below a pre-charge limit, in order to ensure recharging as quickly as possible.

[0018] This eliminates the need for a low-voltage battery to discharge the high-voltage electrical system. The discharge time is independent of the low-voltage battery. This allows for a faster discharge rate, especially at low ambient temperatures.

[0019] According to an advantageous embodiment of the device, the two DC / DC converters in the at least one first low-voltage electrical system can be electrically coupled via an electrical coupling element. This allows 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 can also be permanently electrically coupled to each other on the low-voltage side.

[0020] If two low-voltage electrical systems are present, the two low-voltage electrical systems are coupled by the coupling element.

[0021] According to an advantageous embodiment of the device, the second DC / DC converter can be electrically connected to the high-voltage battery via a safety element. Advantageously, the safety element can be integrated into the second DC / DC converter.

[0022] According to an advantageous embodiment of the device, the second DC / DC converter can be electrically coupled to a second low-voltage electrical system.

[0023] 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, for example, be intended for supplying safety-critical loads.

[0024] According to an advantageous embodiment of the device, the at least one first low-voltage electrical system can include 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 loads, in particular, for example, safety-critical loads.

[0025] According to a further aspect of the invention, a method for discharging a high-voltage electrical system of an electrically operated vehicle is proposed with a device comprising at least 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 into at least one first low-voltage electrical system via a first DC / DC converter; and 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.

[0026] The proposed method makes it possible to actively discharge the high-voltage electrical system with the high-voltage contactors open, not via a load or resistor, but by using 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.

[0027] The first DC / DC converter is located in the high-voltage electrical system and is disconnected from the high-voltage battery and thus the high-voltage power 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, to the first DC / DC converter via a coupling element. This allows energy to be continuously fed from the low-voltage section into the high-voltage battery via the second DC / DC converter, for example, when this energy originates from the high-voltage electrical system via the first DC / DC converter.

[0028] For discharge, 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 electrical system. The second DC / DC converter converts the energy to the high-voltage side, so that energy from the low-voltage electrical system can be fed into the high-voltage battery.

[0029] Active discharge can be terminated when the high-voltage on-board voltage falls below a defined limit, for example below a touch protection extra-low voltage or below a pre-charge limit.

[0030] This eliminates the need for a low-voltage battery to discharge the high-voltage electrical system. The pre-charging time is independent of the low-voltage battery. This allows for increased pre-charging power, especially at low ambient temperatures.

[0031] According to an advantageous embodiment of the method, an electrical coupling element can be closed between the two DC / DC converters before the electrical energy is fed into the at least one first low-voltage 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.

[0032] According to an advantageous embodiment of the method, the discharge 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-charge limit. This ensures that the system's safety limits are adequately maintained.

[0033] According to an advantageous embodiment of the method, a second low-voltage electrical system can be powered directly from the high-voltage battery via the second DC / DC converter. In particular, safety-critical low-voltage loads 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 intended for supplying safety-critical loads.

[0034] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0035] This shows: Fig. 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; Fig. 2 a system overview of a device for discharging a high-voltage electrical system of an electrically powered vehicle according to a further embodiment of the invention; and Fig. 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.

[0036] In the figures, identical or similar components are numbered with the same reference symbols. The figures merely show examples and are not to be understood as limiting.

[0037] Fig. Figure 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.

[0038] 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 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 and 18 are electrically coupled to each other via at least one first low-voltage electrical system 20.

[0039] The second DC / DC converter 18 can also be directly electrically connected to the high-voltage battery 12 via a safety element, which can be integrated, for example, in the second DC / DC converter 18.

[0040] At the in Fig. In the embodiment shown in Figure 1, 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 load 24.

[0041] At least the second DC / DC converter 18 is bidirectional and can both convert electrical energy from the high-voltage battery 12 and feed it into the low-voltage electrical system 20, as well as convert electrical energy from the low-voltage electrical system 20 to the high-voltage side and feed it into the high-voltage battery 12.

[0042] 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.

[0043] 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.

[0044] Before the electrical energy is fed into the at least one first low-voltage electrical system 20, the electrical coupling element 22 between the two DC / DC converters 16, 18 is closed.

[0045] The converted electrical energy from the first low-voltage electrical system 20 is then fed into the high-voltage battery 12 via the second DC / DC converter 18.

[0046] The discharge 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 pre-charge limit to ensure the fastest possible recharging.

[0047] Fig. Figure 2 shows a system overview of a device 100 according to a further embodiment of the invention.

[0048] At the in Fig. In the embodiment shown in Figure 2, the first low-voltage electrical system 20 has a low-voltage battery 28.

[0049] A second low-voltage electrical system 30 is supplied directly from the high-voltage battery 12 via the second DC / DC converter 18.

[0050] The second low-voltage electrical system 30 also includes an optional low-voltage load. One or more loads 26 can be electrically connected to both low-voltage electrical systems 20, 30. In particular, another load 26 can be a safety-critical low-voltage load 26, which can be supplied directly from the high-voltage battery 12 via the second DC / DC converter 18 in the second low-voltage electrical system 30.

[0051] 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 via the electrical coupling element 22 into the second low-voltage electrical system 30 and then fed back into the high-voltage battery 12 via the second DC / DC converter 18.

[0052] Fig. Figure 3 shows a schematic representation of a method for discharging a high-voltage electrical system 10 of an electrically powered vehicle using a device 100 according to an embodiment of the invention. The electrical energy flow is represented by dotted arrows.

[0053] 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. These could be, for example, the intermediate circuit capacitances of the inverter, an air conditioning compressor, an onboard charger, or a heater.

[0054] Before discharge, the high-voltage contactors 14 are opened. The low-voltage coupling element 22 is closed.

[0055] 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.

[0056] The discharge process can be terminated when the high-voltage on-board voltage falls below a defined limit, for example, when the high-voltage on-board voltage falls below a touch protection extra-low voltage or below a pre-charge limit. Reference symbol list 10 High-voltage electrical system 12 high-voltage batteries 14 High-voltage contactors 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 consumers 28 Low-voltage battery 30 second low-voltage electrical system 100 energy storage systems QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 209 105 A1

[0006]

Claims

[1] 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). [2] 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). [3] 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. [4] 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). [5] Device according to one of claims 2 to 4, wherein the first low-voltage vehicle electrical system (20) and the second low-voltage vehicle electrical system (30) are electrically coupled via the electrical coupling element (22). [6] 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). [7] 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 vehicle electrical system (10); Feeding electrical energy from the high-voltage vehicle electrical system (10) via a first DC / DC converter (16) into at least one first low-voltage vehicle electrical system (20); Feeding the electrical energy from the at least one first low-voltage vehicle electrical system (20) into the high-voltage battery (12) via a second, bidirectional, DC / DC converter (18). [8] Method 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). [9] Method 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. [10] Method according to one of claims 7 to 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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