Method for operating an electrically powered vehicle

Abstract

The invention relates to a battery arrangement (1) for an electrically powered vehicle (2), comprising an HV battery (3) with two HV battery cell packs (3.1, 3.2), wherein a first switching element (US1) is arranged between a negative terminal of the first HV battery cell pack (3.1) and a positive terminal of the second HV battery cell pack (3.2). According to the invention, it is provided that - a first terminal of a choke (L) is connected to the negative terminal of the first HV battery cell pack (3.1) or to the positive terminal of the second HV battery cell pack (3.2), - a first voltage equalization switching element (SS1) is arranged between a second terminal of the choke (L) and a positive terminal of the first HV battery cell pack (3.1), and - a second voltage equalization element (SS2) is arranged between the second terminal of the choke (L) and a negative terminal of the second HV battery cell pack (3.2). Furthermore, the invention relates to a method for voltage equalization of two HV battery cell packs (3.1, 3.2) of an HV battery (3) of the battery arrangement (1), an electrically powered vehicle (2) with the battery arrangement (1) and a method for operating the electrically powered vehicle (2).

Description

[0001] The invention relates to a method for operating an electrically powered vehicle according to the preamble of claim 1.

[0002] Systems for switching battery pack voltages and control logic for electric vehicles with multiple battery packs are known from the prior art, as described in US 10,854,933 B2. One method for controlling the operation of a vehicle includes a vehicle controller that receives a voltage switching signal to change a voltage output of the vehicle's battery system. The vehicle controller determines whether the rotational speed of a traction motor is below a calibrated base speed. If so, the vehicle controller transmits a pack isolation signal to an inverter to electrically disconnect the traction battery packs from the traction motor. The vehicle controller also determines whether the bus current of a DC bus is below a calibrated bus current threshold.If this is the case, the vehicle controller transmits an opening signal to open one or more package contactors and a closing signal to close one or more package contactors, causing the vehicle battery system to output the second voltage.

[0003] From DE 10 2018 200 562 A1, a motor vehicle electrical system is known which has an electric machine that can be operated as a motor and generator, a first energy storage device and a second energy storage device, and in which means are provided that are configured to set switching states alternatively to each other in which a) either only the first energy storage device or only the second energy storage device is connected to the electric machine, b) the first energy storage device and the second energy storage device are connected to the electric machine in parallel, and c) the first energy storage device and the second energy storage device are connected to the electric machine in series, wherein a compensating circuit is further provided which is configured to, when in switching state c) the first energy storage device and the second energy storage device are connected to the electric machine in series,to store electrical energy in a first switching state and to release the stored energy to the second energy storage device in a second switching state.

[0004] From DE 10 2023 130 122 A1, a voltage balancing circuit is known, comprising a direct current-to-direct current (DC-to-DC) voltage converter that connects a first battery with a first voltage and a second battery with a second voltage, wherein the DC-to-DC converter transfers electrical power from the first battery to the second battery when the first voltage is greater than the second voltage, and transfers electrical power from the second battery to the first battery when the first voltage is less than the second voltage, wherein the transfer of electrical power from the first battery to the second battery or from the second battery to the first battery balances the electrical power difference between the first battery and the second battery.

[0005] From DE 10 2019 007 868 A1, a storage device for an electrically powered vehicle is known, comprising an electrical energy storage device which has two series-connected sub-strings for storing electrical energy, a charging port for connecting the sub-strings to a charging device in order to supply the electrical energy storage device with electrical energy, a switching device which is electrically connected to the series-connected sub-strings and to an intermediate tap between the sub-strings, and a voltage converter of the switching device for dividing the electrical energy between the sub-strings and for converting the charging voltage of the charging device into a supply voltage different from the charging voltage, wherein the switching device is configured to supply the first sub-string and / or the second sub-string with the charging voltage of the charging device in a first operating state.and in a second operating state to supply the first sub-string or the second sub-string with the supply voltage.

[0006] From EP 4 312 343 A1, a circuit is known comprising a first battery with a positive terminal coupled to a positive transmission line and a negative terminal coupled to a common node, wherein the positive transmission line includes a first contactor; a second battery with a positive terminal coupled to the common node and a negative terminal coupled to a negative transmission line, wherein the negative transmission line includes a second contactor; and a sub-circuit coupled to the common node, to the positive transmission line and to the negative transmission line.

[0007] The invention is based on the objective of providing a method for operating the electrically powered vehicle that is improved compared to the prior art.

[0008] The problem is solved according to the invention by a method for operating an electrically powered vehicle with the features of claim 1.

[0009] Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] A battery arrangement for an electrically powered vehicle comprises a high-voltage (HV) battery with two HV battery cell packs. The HV battery cell packs each contain, in particular, a plurality of electrically connected series and / or parallel rechargeable electrochemical battery cells. The HV battery is, in particular, a traction battery for powering the vehicle; that is, it is specifically intended for supplying electrical energy to at least one electric drive system of the vehicle.

[0011] A first switching element is arranged between the negative terminal of the first high-voltage (HV) battery cell pack and the positive terminal of the second HV battery cell pack. The negative terminal of the first HV battery cell pack can thus be connected to the positive terminal of the second HV battery cell pack by closing the first switching element and disconnected from the positive terminal of the second HV battery cell pack by opening the first switching element. The HV battery cell packs each have, for example, a voltage, in particular a nominal voltage, of 400 V. By closing the first switching element, the two HV battery cell packs can be electrically connected in series. The HV battery with these two electrically series-connected HV battery cell packs then has a voltage, in particular a nominal voltage, that is twice as high as the voltage, in particular a nominal voltage, of the respective HV battery cell pack, i.e., for example, 800 V.

[0012] The battery arrangement is designed so that - a first terminal of a choke is connected to the negative terminal of the first HV battery cell pack or to the positive terminal of the second HV battery cell pack, - a first voltage equalization switching element is arranged between a second terminal of the choke and a positive terminal of the first HV battery cell pack, wherein the second terminal of the choke can be connected to the positive terminal of the first HV battery cell pack by closing the first voltage equalization switching element and can be disconnected from the positive terminal of the first HV battery cell pack by opening the first voltage equalization switching element, and - a second voltage equalization element is arranged between the second terminal of the choke and a negative terminal of the second HV battery cell pack, wherein the second terminal of the choke can be connected to the negative terminal of the second HV battery cell pack by closing the second voltage equalization element and can be disconnected from the negative terminal of the second HV battery cell pack by opening the second voltage equalization element.

[0013] In one embodiment, at least the first switching element is designed as a semiconductor switch. Alternatively, the first switching element can, for example, be designed as a contactor. The first voltage equalization element is, for example, designed as a contactor or semiconductor switch. The second voltage equalization element is, for example, designed as a contactor or semiconductor switch.

[0014] In the method according to the invention, the following is provided for voltage equalization of the two HV battery cell packs of the HV battery of the battery arrangement:

[0015] If the voltage of the first HV battery cell pack is higher than the voltage of the second HV battery cell pack, then energy must be transferred from the first HV battery cell pack to the second HV battery cell pack. The first switching element remains closed or is closed, and the following sequence of steps is carried out: a1) the first voltage equalization element is closed, causing a current to flow through the choke towards the negative terminal of the first HV battery cell pack, b1) then the first voltage equalization element is opened again, c1) thereafter the second voltage equalization switching element is closed, whereby the current, in particular via the still closed first switching switching element, is fed into the second HV battery cell pack, and d1) then the second voltage equalization switching element is opened again, whereby the sequence of steps a1) to d1) is repeated in a clocking fashion until the voltages of the two HV battery cell packs are equalized.

[0016] If the voltage of the second HV battery cell pack is higher than the voltage of the first HV battery cell pack, then energy must be transferred from the second HV battery cell pack to the first HV battery cell pack. The first switching element remains closed or is closed, and the following sequence of steps is carried out: a2) the second voltage equalization element is closed, causing a current to flow through the choke towards the negative terminal of the second HV battery cell pack, b2) then the second voltage equalization switching element is opened again, c2) thereafter the first voltage equalization switching element is closed, whereby the current, in particular via the still closed first switching switching element, is fed into the first HV battery cell pack, and d2) then the first voltage equalization switching element is opened again, whereby the sequence of steps a2) to d2) is repeated in a clocking fashion until the voltages of the two HV battery cell packs are equalized.

[0017] The battery arrangement, particularly its high-voltage (HV) battery, is also referred to as a switching battery, since the first switching element, when closed, allows the two HV battery cell packs to be connected in series, and when opened, allows them to be connected in parallel. The described solution implements a charging circuit by means of which voltage equalization of the two HV battery cell packs is advantageously performed before switching from series to parallel connection. The charging circuit essentially represents a boost / buck converter.

[0018] An electrically powered vehicle, which can be operated using the method according to the invention, comprises the battery arrangement and at least one electric drive. The at least one electric drive, in particular, comprises at least one electric drive motor and at least one inverter. It is provided that - the positive terminal of the first HV battery cell pack is connected to a positive potential connection of the electric drive via a main positive potential line, - the negative terminal of the second HV battery cell pack is connected to a negative potential connection of the electric drive via a negative potential main line, - a second switching element is arranged between the positive terminal of the second HV battery cell pack and the positive potential connection of the electric drive, which is in particular connected to the main positive potential line, and - a third switching element is arranged between the negative terminal of the first HV battery cell pack and the negative potential connection of the electric drive, which is in particular connected to the negative potential main line.

[0019] It is specifically intended that - a first main switching element is arranged in the positive potential main line, wherein the second switching element is connected to the positive potential main line between the first main switching element and the positive terminal of the first HV battery cell pack, and - a second main switching element is arranged in the negative potential main line, wherein the third switching element is connected between the second main switching element and the negative terminal of the second HV battery cell pack to the negative potential main line.

[0020] The positive potential connection of the electric drive is thus connected to the positive terminal of the first HV battery cell pack or, if present, can be connected to the positive terminal of the first HV battery cell pack by closing the first main switching element and can be disconnected from the positive terminal of the first HV battery cell pack by opening the first main switching element.

[0021] The negative potential connection of the electric drive is thus connected to the negative terminal of the second HV battery cell pack or, if present, can be connected to the negative terminal of the second HV battery cell pack by closing the second main switching element and disconnected from the negative terminal of the second HV battery cell pack by opening the second main switching element.

[0022] The positive potential connection of the electric drive can thus be connected to the positive terminal of the second HV battery cell pack by closing the second switching element and, if present, the first main switching element, and disconnected from the positive terminal of the second HV battery cell pack by opening the second switching element and / or, if present, the first main switching element.

[0023] The negative potential connection of the electric drive can thus be connected to the negative terminal of the first HV battery cell pack by closing the third switching element and, if present, the second main switching element, and disconnected from the negative terminal of the first HV battery cell pack by opening the third switching element and / or, if present, the second main switching element.

[0024] In one embodiment, at least the second and / or the third switching element is / are designed as a semiconductor switch. Alternatively, the second and / or the third switching element can, for example, be designed as a contactor. The first main switching element is, for example, designed as a contactor. The second main switching element is, for example, designed as a contactor.

[0025] In the inventive method for operating the electrically powered vehicle, the two HV battery cell packs are switched during vehicle operation from an electrically series connection, in which the two main switching elements, if present, are closed and the first switching element is closed and the second switching element, the third switching element, the first voltage equalization element and the second voltage equalization element are open, to an electrically parallel connection, in particular in the specified sequence, - a current that is drawn, i.e., specifically requested, by the electric drive is reduced, - the above-mentioned voltage equalization procedure is carried out to equalize the voltage of the two HV battery cell packs, - the first toggle switch is opened, - a pre-charging of the vehicle's high-voltage electrical system voltage to the electrically parallel connection of the two high-voltage battery cell packs, i.e., in particular to the voltage of the individual battery cell packs connected in parallel, is carried out, - the third switching element is closed, - the second switching element is closed, and - the current for the electric drive is increased again.

[0026] As an alternative to the above-mentioned sequence of closing first the third toggle switch element and then the second toggle switch element, for example, the second toggle switch element can be closed first and then the third toggle switch element, or the second and third toggle switch elements can be closed simultaneously.

[0027] The pre-charging of the vehicle's high-voltage electrical system voltage to the electrically parallel connection of the two high-voltage battery cell packs is carried out, for example, by a DC / DC converter located in the vehicle's high-voltage electrical system, with the resulting energy being stored in a low-voltage battery, such as a 12V battery, of the vehicle. Alternatively, the pre-charging of the vehicle's high-voltage electrical system voltage to the electrically parallel connection of the two high-voltage battery cell packs is carried out, for example, by controlling the second switching element and / or the third switching element, designed as a semiconductor switch, within a linear range to pre-charge Cx capacities in the electric drive.The second switching element designed as a semiconductor switch and / or the third switching element designed as a semiconductor switch thus serves as a pre-charging resistor during the closing process.

[0028] In one embodiment, the two HV battery cell packs are switched during vehicle operation from the electrically parallel connection, in which the two main switching elements, if present, are closed and the second switching element and the third switching element are closed and the first switching element, the first voltage equalization element and the second voltage equalization element are open, to the electrically series connection by, in particular in the specified sequence, - the current drawn by the electric drive is reduced, - the second toggle switch and the third toggle switch are opened, - a pre-charging of the electric drive and / or the HV on-board power supply to a voltage of the electrically series-connected HV battery cell packs is carried out, - the first switching element is closed, and - the current for the electric drive is increased again.

[0029] Pre-charging the electric drive and / or the high-voltage electrical system to the voltage of the electrically series-connected high-voltage battery cell packs is achieved, for example, by using a recuperation torque, particularly a short one, in the electric drive to raise the high-voltage electrical system voltage to the voltage of the electrically series-connected high-voltage battery cell packs. Alternatively, pre-charging the electric drive and / or the high-voltage electrical system to the voltage of the electrically series-connected high-voltage battery cell packs is carried out, for example, by the DC / DC converter or by another DC / DC converter located in the vehicle's high-voltage electrical system, using energy from the low-voltage battery.Alternatively, the pre-charging of the electric drive and / or the high-voltage electrical system to the voltage of the electrically series-connected high-voltage battery cell packs is carried out, for example, by controlling the first switching element, designed as a semiconductor switch, in a linear range to pre-charge Cx capacitances in the electric drive. The first switching element, designed as a semiconductor switch, thus serves as a pre-charging resistor during the closing process.

[0030] The described solution enables the use of the battery array, particularly the high-voltage battery within this array, for the electrically powered vehicle. Specifically, it is designed so that during vehicle operation, the supply voltage to the electric drive is adjusted depending on its load and speed, specifically from the voltage of the electrically series-connected high-voltage battery cell packs (e.g., 800 V) to the voltage of the electrically parallel-connected high-voltage battery cell packs (e.g., 400 V) and vice versa. This reduces switching losses in the electric drive's inverter. The high-voltage battery cell packs are connected, or can be connected, to the electric drive via several semiconductor switches to enable short switching times.Operating the electric drive at low speeds with the unnecessarily high voltage of the electrically series-connected high-voltage battery cell packs leads to increased switching losses in the inverter. The described solution avoids this by switching the high-voltage battery cell packs to a parallel connection.

[0031] The problem, however, is that during vehicle operation, the electrically series-connected high-voltage (HV) battery cell packs can have different voltages in the two HV battery cell packs due to the load and differences in cell resistance and cell condition, particularly as a result of aging, state of charge, and temperature, especially with advanced cell aging. This makes an immediate switch to an electrically parallel connection of the HV battery cell packs impossible.

[0032] This problem is solved by the charging circuit described above, which enables voltage equalization of the two high-voltage battery cell packs before switching from series to parallel connection. The charging circuit essentially acts as a boost / bubble converter.

[0033] The described solution thus enables switching between the electrically series and parallel connections of the two high-voltage battery cell packs while the vehicle is in operation. Switching between series and parallel connections of the two high-voltage battery cell packs reduces switching losses in the inverter, particularly at low vehicle speeds.

[0034] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0035] This shows: Fig. 1 schematically an electrically powered vehicle with an embodiment of a battery arrangement, Fig. 2 schematically the vehicle with the embodiment of the battery arrangement according to Fig. 1 during driving operation with an electrically series connection of two HV battery cell packs of an HV battery of the battery arrangement, Fig. 3 schematically the vehicle with the embodiment of the battery arrangement according to Fig. 1 during driving operation with an electrically parallel connection of the HV battery cell packs, Fig. 4 schematically an electrically powered vehicle with a further embodiment of the battery arrangement, Fig. 5 schematically the vehicle with the embodiment of the battery arrangement according to Fig. 4 during an initial operating state of an HV battery of the HV battery assembly, and Fig. 6 schematically the vehicle with the embodiment of the battery arrangement according to Fig. 4 during a second operating state of the HV battery.

[0036] Corresponding parts are marked with the same reference symbols in all figures.

[0037] Based on the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. Section 6 below describes a battery arrangement 1 for an electrically powered vehicle 2, a method for voltage equalization of two HV battery cell packs 3.1, 3.2 of an HV battery 3 of the battery arrangement 1, the electrically powered vehicle 2, and a method for operating the electrically powered vehicle 2. The Fig. 1, Fig. 2 to Fig. 3 the electrically powered vehicle 2 with a first embodiment of the battery arrangement 1 and the Fig. 4, Fig. 5 to Fig. 6 the electrically powered vehicle 2 with an improved second embodiment of the battery arrangement 1.

[0038] The electrically powered vehicle 2 has the battery arrangement 1, which comprises the high-voltage battery 3 with the two high-voltage battery cell packs 3.1 and 3.2. A first switching element US1 is arranged between a negative terminal of the first high-voltage battery cell pack 3.1 and a positive terminal of the second high-voltage battery cell pack 3.2. The high-voltage battery cell packs 3.1 and 3.2 each have a voltage of, for example, 400 V. By closing the first switching element US1, the two high-voltage battery cell packs 3.1 and 3.2 can be electrically connected in series. The high-voltage battery 3 with these two electrically series-connected high-voltage battery cell packs 3.1 and 3.2 then has a voltage that is twice the voltage of the respective high-voltage battery cell pack 3, i.e., for example, 800 V.

[0039] The electrically powered vehicle 2 also has at least one electric drive 4. The positive terminal of the first HV battery cell pack 3.1 is connected to a positive terminal of the electric drive 4 via a positive potential main line HV+. The negative terminal of the second HV battery cell pack 3.2 is connected to a negative terminal of the electric drive 4 via a negative potential main line HV-. A second switching element US2 is arranged between the positive terminal of the second HV battery cell pack 3.2 and the positive terminal of the electric drive 4, and is connected to the positive potential main line HV+. A third switching element US3 is arranged between the negative terminal of the first HV battery cell pack 3.1 and the negative potential terminal of the electric drive 4, and is connected to the negative potential main line HV.

[0040] In the examples shown, it is also provided that a first main switching element HS1 is arranged in the positive potential main line HV+, wherein the second switching switching element US2 is connected between the first main switching element HS1 and the positive terminal of the first HV battery cell pack 3.1 to the positive potential main line HV+, and that a second main switching element HS2 is arranged in the negative potential main line HV-, wherein the third switching switching element US3 is connected between the second main switching element HS2 and the negative terminal of the second HV battery cell pack 3.2 to the negative potential main line HV-.

[0041] This design makes it possible to electrically connect the HV battery cell packs 3.1 and 3.2 in series and to connect them to the drive 4, in order to enable the vehicle 2 to be driven with the electrically series-connected HV battery cell packs 3.1 and 3.2, as shown in Fig. 2 shown, or to electrically connect the HV battery cell packs 3.1, 3.2 in parallel with each other and to connect them with the drive 4 in order to enable the vehicle 2 to be driven with the electrically parallel connected HV battery cell packs 3.1, 3.2, as shown in Fig. 3 shown.

[0042] To operate the vehicle 2 with the electrically series-connected HV battery cell packs 3.1, 3.2, the first switching element US1 is closed, thereby connecting the two HV battery cell packs 3.1, 3.2 electrically in series; the two main switching elements HS1, HS2 are closed, thereby connecting the HV battery 3 with the two electrically series-connected HV battery cell packs 3.1, 3.2 to the drive 4; and the second switching element US2 and the third switching element US3 are open, as shown in Fig. 2 shown.

[0043] To operate the vehicle 2 with the electrically parallel-connected HV battery cell packs 3.1, 3.2, the first switching element US1 is open and the second switching element US2 and the third switching element US3 are closed, thereby connecting the two HV battery cell packs 3.1, 3.2 electrically in parallel, and the two main switching elements HS1, HS2 are closed, thereby connecting the HV battery 3 with the two electrically parallel-connected HV battery cell packs 3.1, 3.2 to the drive 4, as shown in Fig. 3 shown.

[0044] By switching the electrical connection of the two HV battery cell packs 3.1, 3.2 from series to parallel during vehicle operation, the supply voltage of the electric drive 4 can be adjusted depending on its load and speed, in particular from the voltage of the electrically series-connected HV battery cell packs 3.1, 3.2 of, for example, 800 V to the voltage of the electrically parallel-connected HV battery cell packs 3.1, 3.2 of, for example, 400 V and vice versa. This allows, in particular, switching losses in an inverter of the electric drive 4 to be reduced.

[0045] The high-voltage battery cell packs 3.1 and 3.2 are connected, or can be connected, to the electric drive 4 via several semiconductor switches to enable short switching times. If the electric drive 4 is operated at low speeds with the unnecessarily high voltage of the electrically series-connected high-voltage battery cell packs 3.1 and 3.2, this leads to increased switching losses in the inverter. In the described solution, this can be avoided by switching the high-voltage battery cell packs 3.1 and 3.2 to an electrically parallel connection.

[0046] However, a problem arises during the operation of vehicle 2 with the electrically series-connected HV battery cell packs 3.1, 3.2. This can lead to voltage differences in the two HV battery cell packs 3.1, 3.2 due to the load and differences in cell resistances and cell states of the battery cells, particularly as a result of aging, state of charge, and temperature, especially with advanced cell aging. Therefore, an immediate switch to the electrically parallel connection of the HV battery cell packs 3.1, 3.2 is not possible.

[0047] This problem is solved by means of a method developed in the Fig. 4, Fig. 5 to Fig. The charging circuit 5 shown in Figure 6 is solved, which additionally features the improved second embodiment of the battery arrangement 1. This charging circuit 5 enables voltage equalization of the two HV battery cell packs 3.1, 3.2 before switching from the electrically series connection to the electrically parallel connection. The charging circuit 5 essentially represents a boost / buck converter.

[0048] This solution thus enables switching from the electrically series connection to the electrically parallel connection of the two HV battery cell packs 3.1, 3.2 and vice versa during the operation of the vehicle 2. By switching from the electrically series connection to the electrically parallel connection of the two HV battery cell packs 3.1, 3.2, switching losses in the inverter can be reduced, especially at low driving speeds of the vehicle 2.

[0049] The charging circuit 5 comprises an inductor L, a first voltage equalization element SS1, and a second voltage equalization element SS2. In the illustrated examples, a first terminal of the inductor L is connected to the negative terminal of the first HV battery cell pack 3.1. The first voltage equalization element SS1 is arranged between a second terminal of the inductor L and the positive terminal of the first HV battery cell pack 3.1. The second voltage equalization element SS2 is arranged between the second terminal of the inductor L and the negative terminal of the second HV battery cell pack 3.2.

[0050] In one embodiment, at least the first switching element US1 is designed as a semiconductor switch.

[0051] In one embodiment, at least the second switching element US2 is designed as a semiconductor switch.

[0052] In one embodiment of the method for operating the electrically powered vehicle 2, the two high-voltage battery cell packs 3.1, 3.2 are switched during vehicle operation from an electrically parallel connection, in which the two main switching elements HS1, HS2 are closed, the second switching element US2 and the third switching element US3 are closed, and the first switching element US1, the first voltage equalization element SS1, and the second voltage equalization element SS2 are open, to an electrically series connection. For this, no voltage equalization of the two high-voltage battery cell packs 3.1, 3.2 by means of the transfer circuit 5 is required. The first voltage equalization element SS1 and the second voltage equalization element SS2 thus remain open.

[0053] To switch the two HV battery cell packs 3.1, 3.2 from electrically parallel to electrically series connection, the current drawn by the electric drive 4 is reduced, the second switching element US2 and the third switching element US3 are opened, the electric drive 4 and / or an HV electrical system is pre-charged to the voltage of the electrically series-connected HV battery cell packs 3.1, 3.2, the first switching element US1 is closed, and the current for the electric drive 4 is increased again. This occurs in the specified sequence.

[0054] The pre-charging of the electric drive 4 and / or the HV electrical system to the voltage of the electrically series-connected HV battery cell packs 3.1, 3.2 is carried out, for example, by using a brief recuperation torque in the electric drive 4 to raise the HV electrical system voltage to the voltage of the electrically series-connected HV battery cell packs 3.1, 3.2. Alternatively, the pre-charging of the electric drive 4 and / or the HV electrical system to the voltage of the electrically series-connected HV battery cell packs 3.1, 3.2 is carried out, for example, by a DC / DC converter arranged in the HV electrical system of the vehicle 2 using energy from a low-voltage battery of the vehicle 2. Alternatively, the pre-charging of the electric drive 4 and / or the HV electrical system to the voltage of the electrically series-connected HV battery cell packs 3.1, 3.2 is carried out by a DC / DC converter arranged in the HV electrical system of the vehicle 2 using energy from a low-voltage battery of the vehicle 2.2, for example, by controlling the first switching element US1, designed as a semiconductor switch, in a linear range to precharge Cx capacitances in the electric drive 4. The first switching element US1, designed as a semiconductor switch, thus serves as a precharging resistor during the closing process.

[0055] In one embodiment of the method for operating the electrically powered vehicle 2, the two high-voltage battery cell packs 3.1, 3.2 are switched during vehicle operation from an electrically series connection, in which the two main switching elements HS1, HS2 are closed and the first switching element US1 is closed and the second switching element US2, the third switching element US3, the first voltage equalization element SS1 and the second voltage equalization element SS2 are open, to an electrically parallel connection. For this, as already mentioned above, the voltage equalization of the two high-voltage battery cell packs 3.1, 3.2 is required by means of the charging circuit 5. This is carried out by means of the method for voltage equalization of the two high-voltage battery cell packs 3.1, 3.2 of the high-voltage battery 3 of the battery arrangement 1.

[0056] To switch the two HV battery cell packs 3.1, 3.2 from the electrically series connection to the electrically parallel connection, the current drawn by the electric drive 4 is reduced.

[0057] Subsequently, the voltage equalization procedure is carried out to equalize the voltage of the two HV battery cell packs 3.1, 3.2.

[0058] If the voltage of the first HV battery cell pack 3.1 is higher than the voltage of the second HV battery cell pack 3.2, then energy must be transferred from the first HV battery cell pack 3.1 to the second HV battery cell pack 3.2, as shown in Fig. 5 shown. The first switching element US1 remains closed and the following sequence of steps is carried out: a1) the first voltage equalization element SS1 is closed, causing a current to flow through the choke L, which flows back towards the negative terminal of the first HV battery cell pack 3.1, b1) then the first voltage equalization element SS1 is opened again, c1) thereupon the second voltage equalization switching element SS2 is closed, whereby the current is fed into the second HV battery cell pack 3.2 via the still closed first switching switching element US1, and d1) then the second voltage equalization switching element SS2 is opened again, whereby the sequence of steps a1) to d1) is repeated in a clocking fashion until the voltages of the two HV battery cell packs 3.1, 3.2 are equalized.

[0059] If the voltage of the second HV battery cell pack 3.2 is higher than the voltage of the first HV battery cell pack 3.1, then energy must be transferred from the second HV battery cell pack 3.2 to the first HV battery cell pack 3.1, as shown in Fig. 6 shown. The first switching element US1 remains closed and the following sequence of steps is carried out: a2) the second voltage equalization element SS2 is closed, causing a current to flow through the choke L, which flows back towards the negative terminal of the second HV battery cell pack 3.2, b2) then the second voltage equalization element SS2 is opened again, c2) thereafter the first voltage equalization switching element SS1 is closed, whereby the current is fed into the first HV battery cell pack 3.1 via the still closed first switching switching element US1, and d2) then the first voltage equalization switching element SS1 is opened again, whereby the sequence of steps a2) to d2) is repeated in a clocking fashion until the voltages of the two HV battery cell packs 3.1, 3.2 are equalized.

[0060] Subsequently, the first switching element US1 is opened, a pre-charge of the vehicle 2's high-voltage (HV) on-board voltage is applied to the electrically parallel connection of the two HV battery cell packs 3.1, 3.2, the third switching element US3 is closed, the second switching element US2 is closed, and the current for the electric drive 4 is ramped up again. The process for switching the two HV battery cell packs 3.1, 3.2 from the electrically series connection to the electrically parallel connection is carried out in the sequence shown.

[0061] The pre-charging of the vehicle 2's high-voltage electrical system voltage to the electrically parallel connection of the two high-voltage battery cell packs 3.1, 3.2 is carried out, for example, by the DC / DC converter located in the vehicle 2's high-voltage electrical system, with the resulting energy being stored in the vehicle 2's low-voltage battery. Alternatively, the pre-charging of the vehicle 2's high-voltage electrical system voltage to the electrically parallel connection of the two high-voltage battery cell packs 3.1, 3.2 is carried out, for example, by controlling the second switching element US2, designed as a semiconductor switch, in a linear range to pre-charge Cx capacities in the electric drive 4. The second switching element US2, designed as a semiconductor switch, thus serves as a pre-charging resistor during the closing process. Reference symbol list 1 Battery arrangement 2 vehicles 3 HV batteries 3.1 First HV battery cell pack 3.2 second HV battery cell pack 4 Drive 5 Transfer circuit HV+ positive potential main line HV - negative potential main line HS1 first main switching element HS2 second main switching element L Throttle SS1 first voltage equalization element SS2 second voltage equalization element US1 first switching element US2 second switching element US3 third switching element

Claims

Method for operating an electrically powered vehicle (2), comprising at least one electric drive (4) and a battery arrangement (1), comprising a high-voltage battery (3) with two high-voltage battery cell packs (3.1, 3.2), wherein a first switching element (US1) is arranged between a negative terminal of the first high-voltage battery cell pack (3.1) and a positive terminal of the second high-voltage battery cell pack (3.2), the negative terminal of the first high-voltage battery cell pack (3.1) can be connected to the positive terminal of the second high-voltage battery cell pack (3.2) by closing the first switching element (US1) and can be disconnected from the positive terminal of the second high-voltage battery cell pack (3.2) by opening the first switching element (US1), and a first connection of a choke (L) is connected to the negative terminal of the first high-voltage battery cell pack (3.1) or to the positive terminal of the second high-voltage battery cell pack (3.2). between a second terminal of the choke (L) and a positive terminal of the first HV battery cell pack (3.1) a first voltage equalization element (SS1) is arranged, the second terminal of the choke (L) can be connected to the positive terminal of the first HV battery cell pack (3.1) by closing the first voltage equalization element (SS1) and can be disconnected from the positive terminal of the first HV battery cell pack (3.1) by opening the first voltage equalization element (SS1), a second voltage equalization element (SS2) is arranged between the second terminal of the choke (L) and a negative terminal of the second HV battery cell pack (3.2), and the second terminal of the choke (L) can be connected to the negative terminal of the second HV battery cell pack (3.2) by closing the second voltage equalization element (SS2) and can be disconnected from the negative terminal of the second HV battery cell pack (3.2) by opening the second voltage equalization element (SS2), wherein the positive terminal of the first HV battery cell pack (3.1) is connected via a positive potential main line (HV+) to a positive potential terminal of the electric drive (4), the negative terminal of the second HV battery cell pack (3.2) is connected via a negative potential main line (HV-) to a negative potential terminal of the electric drive (4), a second switching element (US2) is arranged between the positive terminal of the second HV battery cell pack (3.2) and the positive potential terminal of the electric drive (4), and a third switching element (US3) is arranged between the negative terminal of the first HV battery cell pack (3.1) and the negative potential terminal of the electric drive (4), characterized in that the two HV battery cell packs (3.1, 3.2) during operation of the vehicle (2) from an electrically series connection to an electrically parallel connection by: - ​​reducing a current drawn by the electric drive (4), - equalizing the voltage of the two HV battery cell packs (3.1, 3.2) by, if a voltage of the first HV battery cell pack (3.1) is greater than a voltage of the second HV battery cell pack (3.2) the first switching element (US1) remains closed or is closed and the following sequence of steps is performed: a1) the first voltage equalization switching element (SS1) is closed, b1) then the first voltage equalization switching element (SS1) is opened again, c1) then the second voltage equalization switching element (SS2) is closed, and d1) then the second voltage equalization switching element (SS2) is opened again, with the sequence of steps a1) to d1) being repeated continuously until the voltages of the two HV battery cell packs (3.1, 3.2) are equalized, and by, if the voltage of the second HV battery cell pack (3.2) is greater than the voltage of the first HV battery cell pack (3.1, 3.2),1) the first switching element (US1) remains closed or is closed and the following sequence of steps is performed: a2) the second voltage equalization element (SS2) is closed, b2) then the second voltage equalization element (SS2) is opened again, c2) then the first voltage equalization element (SS1) is closed, and d2) then the first voltage equalization element (SS1) is opened again, whereby the sequence of steps a2) to d2) is repeated continuously until the voltages of the two HV battery cell packs (3.1, 3.2) are equalized, - the first switching element (US1) is opened, - a pre-charge of an HV vehicle electrical system voltage (2) is carried out on the electrically parallel connection of the two HV battery cell packs (3.1, 3.2), - the third switching element (US3) is closed, - the second switching element (US2) is closed, and - the current for the electric drive (4) is increased again. Method according to claim 1, characterized in that: - the pre-charging of the vehicle's (2) HV electrical system voltage to the electrically parallel connection of the two HV battery cell packs (3.1, 3.2) is carried out by a DC / DC converter arranged in an HV electrical system of the vehicle (2) and any resulting energy is stored in a low-voltage battery of the vehicle (2), or - the pre-charging of the vehicle's (2) HV electrical system voltage to the electrically parallel connection of the two HV battery cell packs (3.1, 3.2) is carried out by controlling the second and / or third switching element (US2, US3) designed as a semiconductor switch in a linear range. Method according to claim 1 or 2, characterized in that the two HV battery cell packs (3.1, 3.2) are switched from electrically parallel connection to electrically series connection during the operation of the vehicle (2) by: - ​​reducing the current drawn by the electric drive (4), - opening the second switching element (US2) and the third switching element (US3), - precharging the electric drive (4) and / or the HV electrical system to a voltage of the electrically series-connected HV battery cell packs (3.1, 3.2), - closing the first switching element (US1), and - increasing the current for the electric drive (4) again. The method according to claim 3, characterized in that: - the pre-charging of the electric drive (4) and / or the HV electrical system to the voltage of the electrically series-connected HV battery cell packs (3.1, 3.2) is carried out by using a short recuperation torque in the electric drive (4) to raise the HV electrical system voltage to the voltage of the electrically series-connected HV battery cell packs (3.1, 3.2); or - the pre-charging of the electric drive (4) and / or the HV electrical system to the voltage of the electrically series-connected HV battery cell packs (3.1, 3.2) is carried out by the DC / DC converter or by a further DC / DC converter arranged in the HV electrical system of the vehicle (2) using energy from the low-voltage battery; or - the pre-charging of the electric drive (4) and / or the HV electrical system to the voltage of the electrically series-connected interconnected HV battery cell packs (3.1, 3.2) is carried out by controlling the first switching element (US1), which is designed as a semiconductor switch, in a linear range. Method according to one of the preceding claims, characterized in that at least the first switching element (US1) is designed as a semiconductor switch. Method according to one of the preceding claims, characterized in that a first main switching element (HS1) is arranged in the positive potential main line (HV+), wherein the second switching element (US2) is connected to the positive potential main line (HV+) between the first main switching element (HS1) and the positive terminal of the first HV battery cell pack (3.1), and a second main switching element (HS2) is arranged in the negative potential main line (HV-), wherein the third switching element (US3) is connected to the negative potential main line (HV-) between the second main switching element (HS2) and the negative terminal of the second HV battery cell pack (3.2). Method according to one of the preceding claims, characterized in that at least the second switching element (US2) and / or the third switching element (US3) are designed as a semiconductor switch.

Images