Electric drive arrangement and method for its operation

Abstract

The invention relates to an electric drive arrangement (1), comprising at least one high-voltage battery (2) consisting of a first partial battery (3) and a second partial battery (4), at least one electric drive connected to the high-voltage battery (2), wherein the electric drive has an inverter (5) and an electric machine (6), wherein the high-voltage battery (2) has two high-voltage connections, which can be connected via a charging contactor (8, 9) to two DC charging connections (EVSE_P, EVSE_N) for charging at a DC charging station (EVSE), wherein the high-voltage connections of the high-voltage battery (2) are further connected to an on-board charger (7) which has a plurality of AC charging connections (U, V, W) for connection to an AC charging station, wherein two of the AC charging connections (U, V, W) are further connectable via a switching element (NACS_P, NACS_N) to one of the DC charging connections (EVSE_P, EVSE_N). wherein the electric drive arrangement (1) is configured towhen charging the high-voltage battery (2) at a DC charging station (EVSE), to charge the high-voltage battery (2) via the on-board charger (7) and to transfer one partial battery (3, 4) to the other partial battery (3, 4) and / or vice versa by means of the inverter (5), and then, when the high-voltage battery (2) has been heated to a predetermined target temperature by the transfer, to stop the operation of the inverter (5), to charge in parallel via the charging contactors (8, 9) and then to deactivate the on-board charger (7).

Description

[0001] The invention relates to an electric drive arrangement for a vehicle according to the preamble of claim 1 and a method for its operation according to the preamble of claim 9.

[0002] When spontaneously charging an electrically powered vehicle with a cold battery using DC, only a very low charging power can be achieved, which significantly increases the charging time.

[0003] The DC fast charging time at low temperatures is determined by the battery's maximum tolerable charging current. Damage caused by plating must be avoided here. Increasing the DC charging current without damage can be achieved by heating the battery. Typical considerations in China include the vehicle's charging time at -7°C. This is already a draft charging standard.

[0004] If the vehicle is aware of an upcoming charging stop, for example, through scheduling in a navigation system, the temperature in the cells can be raised in good time by heating the battery while driving. This can be achieved, for example, via a heater in the battery cooling circuit or by intentionally setting an inefficient operating point in the drive system while driving (power wasting).

[0005] However, if the charging stop occurs spontaneously, prior battery heating was not possible. In such cases, an impedance heating process can be used to heat the battery by transferring the charge from one half of the battery to the other half and vice versa. The transfer current is controlled by the inverter. The heating occurs inside the battery cells, precisely where it is needed. The disadvantage is high electrical interference emissions, which require a very large filter to comply with legal EMC requirements.

[0006] An alternative to the impedance heating method is heating with heating mats. However, this only heats the cell externally. Therefore, a certain amount of time is required for the cells to heat up completely. Furthermore, heating mats are difficult to implement with round cells.

[0007] Power wasting can also occur while the vehicle is stationary during the DC charging process. The inverter provides zero torque but generates high reactive current in the electric motor. The resulting heat loss in the inverter and the electric motor can be used to heat the battery via the cooling circuit. A disadvantage is the very long dead time until the waste heat from the electric drive reaches the battery cooling plate (e.g., 10 to 15 minutes). Furthermore, as with impedance heating, significant EMC interference occurs, caused by the inverter. A filter would also be necessary here.

[0008] WO 2024 / 066325 A1 describes a self-heating battery circuit comprising a first battery pack, a second battery pack, a first capacitor, a second capacitor, a plurality of phases of bridge arms, and a plurality of phases of windings corresponding one-to-one to the plurality of phases of bridge arms, wherein each winding phase is connected to the center point of a corresponding bridge arm. A negative electrode of the first battery pack is connected to a positive electrode of the second battery pack. The negative electrode of the first battery pack and the positive electrode of the second battery pack are connected to a neutral point of the plurality of phases of windings. A positive electrode of the first battery pack is connected to a first bus terminal of the plurality of phases of bridge arms. A negative electrode of the second battery pack is connected to a second bus terminal of the plurality of phases of bridge arms.A first end of the second capacitor is connected to a second end of the first capacitor. The first end of the second capacitor and the second end of the first capacitor are connected to the neutral point of the multiple winding phases. A second end of the second capacitor is connected to the negative electrode of the second battery pack. A first end of the first capacitor is connected to the positive electrode of the first battery pack.

[0009] WO 2024 / 045 655 A1 describes a control system and a control method for the self-heating of a battery and an electric means of transport.The control system includes a battery pack, a winding, a first switch assembly, a second switch assembly, a capacitor, and a controller, wherein the battery pack includes a first battery group and a second battery group connected in series, wherein a connecting line is led out between the first battery group and the second battery group, and the connecting line is connected to one end of the winding, wherein the first switch assembly and the second switch assembly are connected in series, wherein the first switch assembly is electrically connected to a positive electrode of the first battery group and a first end of the capacitor, and the second switch assembly is electrically connected to a negative electrode of the second battery group and a second end of the capacitor, wherein the first end and the second end of the capacitor are used for connecting to a load.A midpoint between the first switch assembly and the second switch assembly is connected to the other end of the coil. The controller is electrically connected to the first switch assembly and the second switch assembly, allowing the battery pack to generate heat.

[0010] DE 10 2011 075 927 A1 discloses a power converter circuit designed for the multifunctional conversion of DC voltage to DC voltage, DC voltage to AC voltage, and AC voltage to DC voltage. The circuit comprises a bridge circuit with three half-bridges, chokes connected to the center nodes of the half-bridges, and a switching network. This arrangement enables flexible energy conversion and is particularly suitable for applications in the field of electromobility, such as charging and discharging batteries in electric vehicles.

[0011] The invention is based on the object of providing a novel electric drive arrangement and a novel method for its operation.

[0012] The object is achieved according to the invention by an electric drive arrangement for a vehicle having the features of claim 1 and a method for its operation having the features of claim 9.

[0013] Advantageous embodiments of the invention are the subject of the subclaims.

[0014] An electric drive arrangement for a vehicle is proposed, comprising at least one high-voltage battery, at least one electric drive which is connected to the high-voltage battery, wherein the electric drive has an inverter and an electric machine, wherein the high-voltage battery has two high-voltage connections which can each be connected via a charging contactor to two DC charging connections for charging at a DC charging station, wherein the high-voltage connections of the high-voltage battery are further connected to an on-board charger which has a plurality of AC charging connections for connection to an AC charging station, wherein two of the AC charging connections are further connectable via a switching element to one of the DC charging connections each.According to the invention, it is proposed that the at least one high-voltage battery has at least a first sub-battery and a second sub-battery, the electric drive arrangement is configured to open the charging contactors when charging the high-voltage battery at a DC charging station in a first step, to close the switching elements, to charge the high-voltage battery via the on-board charger and to transfer one sub-battery to the other sub-battery and / or vice versa by means of the inverter, and then, when the high-voltage battery has been heated up to a predetermined target temperature by the transfer, to stop the operation of the inverter in a second step, to close the charging contactors and to charge via the charging contactors in parallel to charging via the on-board charger, and then to deactivate the on-board charger and to continue the charging process exclusively via the charging contactors.

[0015] In one embodiment, the sub-batteries are connected in series.

[0016] In one embodiment, a center tap is provided between the sub-batteries.

[0017] In one embodiment, a star point of the electric machine is connected to the center tap of the high-voltage battery or can be connected via a switch.

[0018] In one embodiment, the on-board charger includes a power factor correction filter and a voltage converter.

[0019] In one embodiment, the voltage converter is designed as an isolating DC / DC converter.

[0020] In one embodiment, the on-board charger further comprises an AC EMC filter connected to the AC charging terminals, and / or PFC chokes and / or a DC EMC filter connected to the high-voltage terminals of the high-voltage battery. Alternatively or additionally, the voltage converter comprises at least one resonant choke, at least one intermediate circuit capacitor, at least one resonant capacitor, and / or a transformer.

[0021] According to one aspect of the present invention, a vehicle having at least one electric drive arrangement as described above is proposed.

[0022] According to one aspect of the present invention, a method for operating the electric drive arrangement as described above when charging the high-voltage battery at a DC charging station is proposed. According to the invention, in a first step, the charging contactors are or will be opened, the switching elements are or will be closed, and the high-voltage battery is charged via the on-board charger, wherein the inverter transfers charges from one sub-battery to the other sub-battery and / or vice versa. When the high-voltage battery has been heated to a predetermined target temperature by the transfer, in a second step, the operation of the inverter is stopped, the charging contactors are closed, and charging is carried out via the charging contactors in parallel with charging via the on-board charger. The on-board charger is then deactivated, and the charging process is continued exclusively via the charging contactors.

[0023] In one embodiment, the target temperature of the high-voltage battery during the transition from the first step to the second step is selected such that the battery temperature is sufficiently high to achieve the shortest possible charging process. The target temperature is particularly dependent on the state of charge and battery temperature. The lower the state of charge of the high-voltage battery, the higher the charging current that can be selected. Regarding the battery temperature, a cold high-voltage battery has a lower permissible charging current, while a warm high-voltage battery allows a higher charging current.

[0024] For example, a high-voltage battery with a state of charge of 10% must be heated to approximately 0°C before the charging contactors at the DC charging station can be closed and the charging process can begin via a high DC current from the DC charging station directly to the high-voltage battery. Due to the low battery state of charge, the high-voltage battery is not damaged (e.g., because the maximum terminal voltage is not exceeded), even though the DC charging current is high. Due to the high charging current, the high-voltage battery also continues to heat up during the charging process, contributing to a further increase in the maximum charging current.

[0025] At an average high-voltage battery state of charge, for example, 50%, the permissible charging current is reduced. If the battery is still cold, this permissible charging current is reduced even further. At a state of charge of approximately 50%, the high-voltage battery needs to be warmed to approximately 15°C to allow a higher charging current, which can also cause the battery to heat up further during the charging process.

[0026] Furthermore, in addition to temperature and state of charge, charging currents also depend on the chemical composition of the battery cells. The above examples therefore serve only as a guideline for the current state of battery cells (especially for NMC batteries).

[0027] The charging process can be carried out in two steps: In a first step, the DC charging process takes place via the on-board charger. The charging contactors are open. The inverter is active and heats the battery through charge transfer (impedance heating process). The EMC interference caused by the inverter is dampened by the on-board charger's filter components. In a second step, the inverter stops the impedance heating process once the battery has heated to a setpoint. The charger initially remains in operation. The charging contactors are closed, and a portion of the charging current can flow parallel to the on-board charger due to the direct connection of the charging station to the vehicle battery. The on-board charger can now be deactivated.

[0028] The inventive solution enables the charging process to be accelerated at low temperatures compared to battery heating by heating the cooling water (heater or power washer in electric drive systems) or by using heating mats. An EMC filter can be avoided or significantly reduced in size.

[0029] The invention aims to enable the implementation of an impedance heating process during the DC charging process. This should make it clear to the customer that the charging process has begun (a low DC charging current is applied), and the vehicle can communicate a predicted charging time to the customer.

[0030] Embodiments of the invention are explained in more detail below with reference to a drawing.

[0031] It shows: Fig. 1 a schematic view of an electric drive arrangement of a vehicle.

[0032] The only Fig. 1 is a schematic view of an electric drive arrangement 1 of a vehicle, for example a passenger car, a commercial vehicle or a bus.

[0033] The electric drive arrangement 1 has a high-voltage battery 2, which is constructed from a series connection of a first sub-battery 3 and a second sub-battery 4 with a center tap between the sub-batteries 3, 4. Furthermore, at least one electric drive, comprising an inverter 5 and an electric machine 6 (symbolized here by three inductors L1, L2, L3 of a stator), is provided, which is connected to the high-voltage battery 2. A star point 15 of the electric machine 6 is connected to the center tap of the high-voltage battery 2. The high-voltage battery 2 has two high-voltage connections, each of which can be connected via a charging contactor 8, 9 to DC charging connections EVSE_P, EVSE_N for charging at a DC charging station EVSE in order to charge the high-voltage battery 2.

[0034] The high-voltage connections of the high-voltage battery 2 are further connected to an on-board charger 7, which has AC charging connections U, V, W for connection to an AC charging station in order to charge the high-voltage battery 2.

[0035] The Fig.The topology of the on-board charger 7 shown in Figure 1 is exemplary and comprises a power factor correction filter 10 and a voltage converter 11, for example, an isolating DC / DC converter 11, as well as EMC-effective subcomponents, including an AC filter 12 or AC-EMC filter 12 connected to the AC charging terminals U, V, W; inductances, such as PFC chokes L4, L5, L6 and / or at least one resonant choke L7; capacitors, such as at least one intermediate circuit capacitor C1 and / or a resonant capacitor C2, a transformer T, and a DC-EMC filter 13 connected to the high-voltage terminals of the high-voltage battery 2. Two of the AC charging terminals U, V, W can furthermore be connected to one of the DC charging terminals EVSE_P, EVSE_N via a switching element NACS_P, NACS_N each.

[0036] The charging process is divided into two time periods: In a first step, the vehicle is DC-charged via the on-board charger 7. The charging contactors 8, 9 are open. The DC charging station EVSE is connected to the vehicle's high-voltage system via the closed switching elements NACS_P and NACS_N and the on-board charger 7. A voltage isolation circuit 14 of the AC charging terminals U, V, W is open. The inverter 5 is active and charges one sub-battery 3, 4 into the other sub-battery 3, 4 and / or vice versa, for example, using the impedance heating method known in the prior art. EMC interference from the inverter 5 is prevented from propagating via the DC charging cable to the DC charging station EVSE by the open charging contactors 8, 9 and the filtering effect of the on-board charger 7 with its subcomponents, in particular the DC EMC filter 13, the transformer T, the LC elements (low-pass filters) consisting of the resonant choke L7 and the resonant capacitor C2, and the AC EMC filter 12, or is strongly attenuated.

[0037] In this case, the charging power to the high-voltage battery 2 is the AC charging power of the on-board charger 7 less a power loss in the electric drive and in the high-voltage battery 2.

[0038] In a second step, the charging contactors 8, 9 are closed and DC charging continues directly from the DC charging station EVSE via the charging contactors 8, 9 to the high-voltage battery 2. Once the high-voltage battery 2 has been heated to a predetermined target temperature by the impedance heating process, the operation of the inverter 5 is stopped. Charging continues via the on-board charger 7 to prevent charging from being interrupted due to an interruption in the charging current. In parallel with charging via the on-board charger 7, the charging contactors 8, 9 are closed, whereby the DC charging station EVSE is now directly coupled to the high-voltage battery 2 as a parallel path. The on-board charger 7 is then deactivated, and the charging process takes place exclusively via the charging contactors 8, 9.The target temperature of the high-voltage battery 2 during the transition from the first step to the second step can be selected so that the battery temperature is sufficiently high to achieve the shortest possible charging process, i.e. battery heating due to the DC charging process with the high DC charging current can be taken into account.

[0039] The following additional components are required compared to a conventional impedance heating process, including EMC filters: - Voltage isolation 14 of the AC charging terminals U, V, W, - Switching elements NACS_P and NACS_N for connecting the DC charging station EVSE with the on-board charger 7. List of reference symbols 1 drive arrangement 2 high-voltage batteries 3 partial batteries 4 partial batteries 5 inverters 6 electric machine 7 on-board chargers 8 Charging contactor 9 Charging contactor 10 power factor correction filters 11 Voltage converters, DC / DC converters 12 AC filters, AC EMC filters 13 DC EMC filters 14 Voltage isolation 15 Star Point C1 DC link capacitor C2 resonance capacitor EVSE DC charging station EVSE_N DC charging port EVSE_P DC charging port L1, L2, L3 inductance L4, L5, L6 PFC choke L7 Resonance choke NACS_N switching element NACS_P switching element T Transformer U, V, W AC charging port

Claims

[1] An electric drive arrangement (1) for a vehicle, comprising at least one high-voltage battery (2), at least one electric drive connected to the high-voltage battery (2), the electric drive having an inverter (5) and an electric machine (6), the high-voltage battery (2) having two high-voltage connections, each of which can be connected via a charging contactor (8, 9) to two DC charging connections (EVSE_P, EVSE_N) for charging at a DC charging station (EVSE), the high-voltage connections of the high-voltage battery (2) being further connected to an on-board charger (7) having a plurality of AC charging connections (U, V, W) for connection to an AC charging station, two of the AC charging connections (U, V, W) being further connectable via a switching element (NACS_P, NACS_N) to one of the DC charging connections (EVSE_P, EVSE_N), characterized bythat the at least one high-voltage battery (2) has at least a first partial battery (3) and a second partial battery (4), the electric drive arrangement (1) is configured, when charging the high-voltage battery (2) at a DC charging station (EVSE), to open the charging contactors (8, 9) in a first step, to close the switching elements (NACS_P, NACS_N), to charge the high-voltage battery (2) via the on-board charger (7) and to transfer one partial battery (3, 4) to the other partial battery (3, 4) or vice versa by means of the inverter (5), and then, when the high-voltage battery (2) has been heated up to a predetermined target temperature by the transfer, to stop the operation of the inverter (5) in a second step, to close the charging contactors (8, 9) and to charge via the charging contactors (8, 9) in parallel to the charging via the on-board charger (7), and subsequently to deactivate the on-board charger (7) and to carry out the charging process exclusively via the loading contactors (8, 9). [2] Electric drive arrangement (1) according to claim 1, characterized by that the partial batteries (3, 4) are connected in series with each other. [3] Electric drive arrangement (1) according to claim 2, characterized by that a center tap is provided between the partial batteries (3, 4). [4] Electric drive arrangement (1) according to claim 3, characterized by that a star point (15) of the electric machine (6) is connected to the center tap of the high-voltage battery (2) or can be connected via a switch. [5] Electric drive arrangement (1) according to one of the preceding claims, characterized by that the on-board charger (7) has a power factor correction filter (10) and a voltage converter (11). [6] Electric drive arrangement (1) according to claim 5, characterized by that the voltage converter (11) is designed as an isolating DC / DC converter (11). [7] Electric drive arrangement (1) according to claim 5 or 6, characterized bythat the on-board charger (7) further comprises an AC EMC filter (12) which is connected to the AC charging terminals (U, V, W) and / or PFC chokes (L4, L5, L6) and / or a DC EMC filter (13) which is connected to the high-voltage terminals of the high-voltage battery (2), and / or that the voltage converter (11) comprises at least one resonance choke (L7), at least one intermediate circuit capacitor (C1), at least one resonance capacitor (C2) and / or a transformer (T). [8] Vehicle with at least one electric drive arrangement (1) according to one of the preceding claims. [9] Method for operating an electric drive arrangement (1) according to one of claims 1 to 7 when charging a high-voltage battery (2) at a DC charging station (EVSE), characterized byin that in a first step the charging contactors (8, 9) are or become open, the switching elements (NACS_P, NACS_N) are or become closed and the high-voltage battery (2) is charged via the on-board charger (7), wherein the inverter (5) transfers the charges from one partial battery (3, 4) to the other partial battery (3, 4) and / or vice versa, wherein when the high-voltage battery (2) has been heated up to a predetermined target temperature by the transfer, in a second step the operation of the inverter (5) is stopped, the charging contactors (8, 9) are closed and charging is carried out via the charging contactors (8, 9) in parallel with charging via the on-board charger (7), wherein the on-board charger (7) is subsequently deactivated and the charging process is continued exclusively via the charging contactors (8, 9). [10] Method according to claim 9, characterized bythat the target temperature of the high-voltage battery (2) during the transition from the first step to the second step is selected so that the battery temperature is sufficiently high to achieve the shortest possible charging process.

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