Method for operating an onboard electrical system

Abstract

The invention relates to a method for operating an onboard electrical system (10) for an electrically operated vehicle. According to the method, in the charging mode of the vehicle, a power factor correction unit (16) of a vehicle charger unit (14) is used as a DC boost converter for supplying voltage to a load (12) if the load requires a supply of DC voltage that is higher than a maximum DC voltage provided by the charging station.

Description

[0001] 202300918

[0002] 1

[0003] Description

[0004] Method for operating an on-board power supply

[0005] The invention relates to a method for operating an on-board electrical system, in particular an electrically powered vehicle.

[0006] Electric vehicles typically have a high-voltage battery that serves as the vehicle's traction battery. Battery supply voltages for the high-voltage battery are usually specified in voltage classes. Typical voltage classes for electric vehicles include the 400V class and the 800V class. Battery supply voltages in the 400V class can reach up to 500V.

[0007] Battery supply voltages in the 800V class can range from over 500V to 1000V. 800V battery electric vehicles (BEVs) can only be charged at a DC charging station if the charging station can supply DC voltage in the 800V range, i.e., 500V or more. If the charging station can only supply a maximum of 400V (i.e., a maximum of 500V DC, as is common with conventional, so-called legacy charging stations), the 800V BEV cannot be charged, or not fully charged. In such a case, an intermediate step is required to convert the 400V DC voltage to the 800V DC voltage (often referred to as DC boosting).

[0008] One possibility is to use the concept of a switchable battery, where the high-voltage battery has several battery packs with the same number of cells, so that the battery is divided into battery packs, usually two, of 400V each. These two battery packs can be connected in parallel if the charging station can only supply DC voltages in the 400V range. In ferry operation, the two 400V battery packs would then be connected in series to provide DC voltages in the required range for the propulsion system.

[0009] However, one problem with the concept of the switchable battery is that, particularly when charging with a 400V DC charging station, 800V consumers, such as auxiliary equipment of the vehicle electrical system, for example an air conditioning unit or the like, can only be operated if... 202300918

[0010] 2. If an additional high-performance converter is on board that can step up the 400V to 800V. If such a converter is not present, for example because it is expensive, only 400V auxiliary equipment could be used. Conversely, an 800V BEV would require a high-performance step-down converter (often called a DC buck converter) to supply 400V auxiliary equipment with voltage, for example, while charging.

[0011] The object of the invention is to provide a method for operating an on-board electrical system that can easily and cost-effectively overcome at least some of the disadvantages described above. Furthermore, it is an object of the invention to systematically develop the application areas of existing on-board electrical systems of electric vehicles so that, for example, high-voltage consumers can be supplied with voltage independently of the voltage level of the traction battery (400V or 800V battery) in both legacy charging mode and ferry operation.

[0012] These and other problems, which become clear upon studying the present description, are solved by the method according to independent claim 1. Preferred embodiments are the subject of the dependent claims.

[0013] According to one aspect of the invention, a method for operating an on-board electrical system of an electrically powered vehicle is provided, wherein the vehicle has at least one DC load which can be supplied with DC voltage in a first DC supply area, and wherein the on-board electrical system comprises: a vehicle charger unit with at least one power factor correction unit (usually referred to as PFC in English), a traction battery unit for powering the vehicle, a switching unit for selectively connecting the vehicle charger unit to the traction battery unit and / or the DC load, and a charging station connection unit which is functionally connected to the switching unit, the traction battery unit and the power factor correction unit and is designed for connection to a DC charging station.wherein the DC charging station provides DC voltage in a second DC supply area. The method according to the invention comprises the following steps: Determining whether the vehicle is connected to the DC charging station for charging, and, if it has been determined that the vehicle is connected to the DC charging station, 202300918,

[0014] 3

[0015] Determine that the first DC supply area is larger than the second DC supply area; switch the switching unit such that the DC load is connected to the DC charging station via the power factor correction unit; and supply the DC load with DC voltage in the first DC supply area by up-converting a DC voltage provided by the DC charging station in the second DC supply area using the power factor correction unit of the vehicle charger unit, without supplying the DC load with voltage via the traction battery unit.

[0016] The method is based on the idea of ​​using the power factor correction unit (PFC) of the vehicle's charging system (usually referred to as an on-board charger or OBC), which is typically present in the charging system if it is designed for AC charging, as a DC booster. The idea is to use the PFC of the OBC as a DC booster, for example, when charging the vehicle at a legacy charging station that can provide the second DC supply range (e.g., in the 400V class). This allows DC loads that require a first DC supply range (e.g., 800V) to be supplied with DC voltage from the legacy charging station without using the traction battery to power the loads.For this purpose, in 400V charging mode, a direct path between the output of the traction battery and the input of the DC load is interrupted, preferably by means of a switch located therein, and the DC load is connected to the DC charging station via the power factor correction unit to supply the load with voltage via the legacy charging station. This enables upward compatibility for legacy charging processes, even for 800V DC loads.

[0017] Preferably, the method further comprises the following steps: If it has been determined that the vehicle is connected to the DC charging station, charging the traction battery unit by the DC charging station via the power error correction unit, if a DC supply area of ​​the traction battery unit is greater than the second 202300918

[0018] 4

[0019] The DC supply area of ​​the DC charging station, or charging of the traction battery unit by the DC charging station bypassing the power error correction unit, is possible if the DC supply area of ​​the traction battery unit coincides with the second DC supply area of ​​the DC charging station. In other words, when charging at a legacy charging station, the 800V traction battery unit can be charged via the PFC using DC boost, or the 400V traction battery unit (if a 400V drive were present) can be charged directly via the legacy charging station. With an 800V traction battery unit, both the load and the traction battery unit would be supplied with (up-converted) voltage via the PFC of the OBC.

[0020] Preferably, when charging the traction battery via the DC charging station using the power error correction unit, if one DC supply area of ​​the traction battery unit is larger than the second DC supply area of ​​the DC charging station, a switch located in a positive current path between the DC charging station and the traction battery is opened. The term "positive current path" refers to a current path that is connected to the positive terminal of the traction battery after the charging station connection unit.

[0021] It is possible that the traction battery unit has several battery units that can be connected in parallel, providing DC voltage in a third DC supply area that is equal to the second DC supply area but smaller than the first. In such a case, the procedure includes the following steps: once it has been determined that the vehicle is connected to the DC charging station, the battery units are connected in parallel, and the parallel-connected battery units are charged by the DC charging station, bypassing the power factor correction unit. In other words, there could be two switchable 400V batteries in the vehicle's electrical system.In such a case, the PFC unit would be used as a DC boost to supply the DC load, and the legacy charging station would be used to charge the 400V battery units, bypassing the PFC unit. 202300918.

[0022] 5

[0023] Preferably, the method further comprises the following steps: If it has been determined that the vehicle is not connected to the DC charging station, switching the switching unit such that the traction battery unit is connected to the DC load, and supplying the DC load with DC voltage from the traction battery unit in the second DC supply range, bypassing the power factor correction unit, if a DC supply range of the traction battery unit coincides with the first DC supply range of the DC load. In other words, in non-charging mode, i.e., for example, when the vehicle is in operation, the DC load is supplied with voltage from the traction battery unit, provided the DC supply ranges match, i.e., for example, in the case of an 800V load and an 800V traction battery unit.

[0024] If the traction battery unit has several battery units that can be connected in parallel and provide DC voltage in a third DC supply area that is equal to the second DC supply area and smaller than the first DC supply area, the procedure comprises the following further steps: If it has been determined that the vehicle is not connected to the DC charging station, determine that the third DC supply area is smaller than the first DC supply area; switch the switching unit such that a positive terminal of at least one of the several battery units is connected to an input of the power error correction unit and an output of the power error correction unit is connected to the DC load;and supplying the DC load with DC voltage in the first DC supply area by up-converting a DC voltage provided by the battery unit connected to the power correction unit in the third DC supply area using the power correction unit. In other words, two switchable 400V battery units could be used in an 800V powertrain. In such a case, a positive terminal of one of the two battery units would be connected to the PFC input, so that the 400V of the battery unit connected to the PFC input would be up-converted to 800V by DC boost using the PFC unit to supply the 800V load from the 400V battery unit. 202300918;

[0025] 6

[0026] Further features and functions of the present invention will become apparent to the person skilled in the art by carrying out the teaching presented here and by examining the accompanying drawings. These show:

[0027] FIG 1 shows a schematic view of an on-board network that can be operated by the method according to the invention, wherein a charging operation is shown in FIG 1.

[0028] FIG 2 shows a schematic view of an on-board network that can be operated by the method according to the invention, wherein a ferry operation is shown in FIG 2.

[0029] FIG 3 shows a schematic view of an on-board power supply with switchable battery units, which can be operated by the method according to the invention, wherein a charging operation is shown in FIG 3.

[0030] FIG 4 shows a schematic view of an on-board network with switchable battery units, which can be operated by the method according to the invention, wherein a ferry operation is shown in FIG 4.

[0031] Elements of the same function or construction are provided with the same reference symbols across all figures.

[0032] Reference is first made to FIG. 1, which shows a schematic view of an electrical system 10 for an electric vehicle (BEV). The electrical system 10 has at least one electrical load, in particular a DC electrical load 12, such as an air conditioner, etc. The electrical load 12 is operated with a first DC supply. This is, for example, a maximum of 800 V. In other words, a supply via a 400 V DC charging station might not be sufficient to provide the required 800 V for the load.

[0033] The vehicle electrical system 10 also includes a vehicle charging unit 14. This is also often referred to as an onboard charger (OBC). In this specific case, the OBC is an AC-OBC, meaning an OBC that can also process alternating current and can be used at an AC charging station. The OBC 14 has a 202300918 connector for this purpose.

[0034] 7

[0035] Power factor correction unit 16 (PFC for short) and an associated DCDC converter 18. PFC and DCDC converter are typical components in an AC-OBC.

[0036] The vehicle electrical system 10 also includes a traction battery unit 20. In the specific example of FIG 1, this unit 20 includes a high-voltage battery, which is, for example, an 800V high-voltage battery.

[0037] The vehicle electrical system 10 further includes a charging station connection unit 22, which is schematically indicated by the dashed box 22. In this specific example, the contactors are shown within the box 22, but in other embodiments they can also be arranged separately from the unit 22. The unit 22 is designed, among other things, to be connected to a charging station, such as a DC charging station 24. The DC charging station 24 provides a DC voltage in a second DC supply area. "Supply" means that it can, for example, supply voltage to consumers such as the consumer 12 or the traction battery unit 20.

[0038] The on-board network 10 also includes a switching unit. This can consist of several switches or switching groups, etc. For example, switches 26, 28, 30, 32 and 32a can belong to the switching unit.

[0039] In FIG. 1, switches 22, 26, 28, 30, and 32 are shown as "CLOSED" or "closed". Switch 32a is shown as "OPEN" or "OPEN".

[0040] The method according to the invention provides for the detection of whether the vehicle is connected to the DC charging station 24 for charging. This can be done, for example, by the charging station connection unit 22, but also by other units. Once the charging operation has been detected, it is determined whether the first DC supply area of ​​the consumer 12 is larger than the second DC supply area of ​​the DC charging station 24. For example, it is determined that the charging station 24 is a legacy charging station, i.e., a charging station of the 400V class, but that the traction battery unit 20 and the consumer 12 require 800V DC. 202300918

[0041] 8

[0042] If it is determined that the first DC supply area is larger than the second DC supply area, the switching unit is configured so that the load 12 is connected to the charging station 24 via the power factor correction unit 16. This can be achieved, for example, by closing switches 22, 26, 28, 30, and 32 during charging operation. Additionally, switch 32a is opened. With this switch configuration, both the load 12 and the traction battery unit 20 are supplied with voltage by the legacy charging station via the PFC unit 16.

[0043] In the switching unit configuration shown in FIG. 1, the high-voltage battery of the traction battery unit 20 can also be charged by the legacy charging station 24 during charging operation. In other words, it is possible to use the 400V class legacy charging station 24 to charge the 800V traction battery unit 20, since the power factor correction unit 16 is used as a DC booster or up-converter. In the example shown in FIG. 1, the PFC or power factor correction unit 16 of the OBC or vehicle charger unit 14 would therefore be used as a DC booster to supply the load 12. This eliminates the need for a separate DC-DC converter. Simultaneously, the traction battery unit 20 can also be charged.

[0044] Reference is now made to FIG 2, which shows a non-charging operation or ferry operation.

[0045] During ferry operation, switches 22, 26, and 28 are open, and switches 30 and 32 are closed. Switch 32a can be either open or closed. For this reason, switch 32a is not shown in FIG. 2.

[0046] In other words, in such a switch configuration, the consumer 12 is supplied with voltage from the 800V battery of the traction battery unit 20. If a non-charging or driving mode is detected, the switching unit can be switched accordingly to achieve the configuration shown in FIG. 2.

[0047] Reference is now made to FIG. 3, which shows a charging operation. In the embodiment of FIG. 3, the on-board electrical system 10 has two switchable battery units, each of which supplies voltage in a third DC voltage supply area, which is identical to the second 202300918

[0048] 9

[0049] The DC supply range can be smaller than the first DC supply range of the load 12. For example, two switchable 400V battery units are available. These can be switched in series or parallel using switches 34, 36. The parallel connection is shown in FIG. 3.

[0050] The method detects that charging is in progress. The switching unit is configured so that the battery units are connected in parallel, for example, with switch 34 open and switches 36 closed. The legacy charging station 24 can charge the battery units because their DC supply ranges match. The method further provides that the 800V load 12 is supplied with voltage from the legacy charging station 24 via DC boost through the power factor correction unit 16, without the load 12 being supplied with voltage from the traction battery unit 20. This is illustrated in FIG. 3 by the closed switches 22, 26, 28, 30 and the open switch 32. In the case of a switchable battery unit, the switch 32a mentioned in connection with FIGS. 1 and 2 is not strictly necessary, can therefore be omitted, and is thus not shown in FIG. 3.

[0051] It is now shown on FIG 4, which shows the non-charging operation or ferry operation, in the case that the on-board electrical system has the switchable battery units, as in FIG 3.

[0052] The procedure detects that the vehicle is not connected to charging station 24. It further determines that the third DC supply area is smaller than the first DC supply area. The switching unit is then configured such that a positive terminal of at least one of the two switchable battery units is connected to an input of the power error correction unit 16, and an output of the power error correction unit 16 is connected to the load 12, without establishing a direct connection between the load 12 and the traction battery unit 20. This can be achieved, for example, by opening switches 22 and 32 and closing switches 26, 28, and 30. The voltage of the battery unit connected to the PFC input is stepped up by the power correction unit 16 to supply the load 12 in the first DC supply area.At the same time, the switchable battery units are connected in such a way that they, for example, correspond to the 202300918.

[0053] 10

[0054] An 800V drive train is available. Opening switch 32 ensures that the 400V battery unit is connected to the load 12 only via the power factor correction unit 16. Direct supply from the traction battery unit 20 is impossible because switch 32 is open. Only the path via the PFC 16 is possible. In the case of a switchable battery unit, switch 32a, mentioned in connection with FIGS. 1 and 2, is not strictly necessary, can therefore be omitted, and is thus not shown in FIG. 4. If switch 32a were present, it would have to be closed.

Claims

202300918 11 Patent claims 1. Method for operating an on-board electrical system (10) of an electrically powered vehicle, which has a DC load (12) that can be supplied with DC voltage in a first DC supply area, wherein the on-board electrical system (10) comprises: a vehicle charger unit (14) with at least one power factor correction unit (16), a traction battery unit (22) for powering the vehicle, a switching unit for connecting the vehicle charger unit (14) to the traction battery unit (20) and / or the DC load (12), and a charging station connection unit (22) that is functionally connected to the switching unit, the traction battery unit (20) and the power factor correction unit (16) and is configured for connection to a DC charging station (24), wherein the DC charging station (24) provides DC voltage in a second DC supply area, wherein the method comprises the following steps: Determine whether the vehicle is connected to the DC charging station (24) for charging, and if it has been determined that the vehicle is connected to the DC charging station (24), Determine that the first DC power supply area is larger than the second DC power supply area, Switching the switching unit such that the consumer (12) is connected to the DC charging station (24) via the power factor correction unit (16), and Supplying the DC load with DC voltage in the first DC supply area by up-converting a DC voltage provided by the DC charging station (24) in the second DC supply area by means of the power factor correction unit (16) of the vehicle charger unit (14), without supplying the DC load (12) with voltage by the traction battery unit (20).

2. The method according to claim 1, further comprising the step: 202300918 12 if it has been determined that the vehicle is connected to the DC charging station (24), Charging the traction battery unit (20) by the DC charging station (24) via the power error correction unit (16) if one DC supply area of ​​the traction battery unit (20) is larger than the second DC supply area of ​​the DC charging station (24), or Charging the traction battery unit (20) by the DC charging station (24) bypassing the power error correction unit (16) when the DC supply area of ​​the traction battery unit (20) coincides with the second DC supply area of ​​the DC charging station (24).

3. The method of claim 2, wherein the traction battery unit (20) comprises several battery units connectable in parallel to one another, which provide DC voltage in a third DC supply area, which is equal to the second DC supply area and smaller than the first DC supply area, and wherein the method further comprises the steps: when it has been determined that the vehicle is connected to the DC charging station (24): Connecting the battery units in parallel, and Charging the parallel connected battery units by the DC charging station (24) bypassing the power factor correction unit (16).

4. A method according to any of the preceding claims, further comprising: if it has been determined that the vehicle is not connected to the DC charging station (24) is connected, Switching the switching unit such that the traction battery unit (20) is connected to the DC load (12), and Supplying the DC load (12) with DC voltage in the second DC supply area from the traction battery unit (20) bypassing the power factor correction unit (16) if a DC supply area of ​​the traction battery unit (20) coincides with the first DC supply area of ​​the DC load (12). 202300918 13 5. The method of claim 4, wherein, if the traction battery unit (20) has several battery units that can be connected in parallel and provide DC voltage in a third DC supply area, which is equal to the second DC supply area and smaller than the first DC supply area, the method further comprises the following steps: if it has been determined that the vehicle is not connected to the DC charging station (24): Determine that the third DC power supply area is smaller than the first DC power supply area, Switching the switching unit such that a positive terminal of at least one of the several battery units is connected to an input of the power error correction unit (16) and an output of the power error correction unit (16) is connected to the DC load (12), and Supplying the DC load (12) with DC voltage in the first DC supply area by up-converting a DC voltage provided by the battery unit connected to the power correction unit (16) in the third DC supply area by means of the power correction unit (16).

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