Vehicle with an electric drive system

Abstract

The invention relates to a vehicle (1) with an electric drive system, comprising - a high-voltage battery (2), - at least two electrical machines (3.1, 3.2) which are mechanically coupled or can be coupled to one another, each having at least one associated electrical inverter (5.1, 5.2), and - a charging port (11), - a control device, - a first high-voltage system (8.1), to which the high-voltage battery (2) and a first inverter (5.1) are connected, and a second high-voltage system (8.2), to which a second inverter (5.2) is connected, wherein the second high-voltage system (8.2) can be selectively coupled to or separated from the first high-voltage system (8.1) via a separating element (7), wherein the control device is configured for charging the high-voltage battery (2) at a charging station (4) with a maximum DC output voltage that is lower than the nominal voltage of the high-voltage battery (2), - to connect the second inverter (5.2) to the charging connection (11) via charging contactors (9) while the isolating element (7) is open, so that the second inverter (5.2) is supplied with electrical power by the charging station (4) and drives the second electrical machine (3.2), which drives the first electrical machine (3.1) via the mechanical connection (6), - to rectify the energy induced there via the first inverter (5.1) and to charge the high-voltage battery (2) with it.

Description

The invention relates to a vehicle with an electric drive system according to the preamble of claim 1.For an electrically driven vehicle with a voltage level of 800 V, for example, it is only possible to charge on DC charging columns whose maximum output voltage is equal to or higher than the DC end-of-charge voltage. However, some (older) DC charging stations provide only a maximum DC voltage of 500 V, so that the vehicle cannot be charged here.Until now, this problem has been solved, for example, by the following measures:switching battery (switching series connection in parallel connection of battery strings or alternating charging of battery strings). A disadvantage here is that additional contactors and busbars are required in the battery. This causes additional costs and restricts the installation space for battery cells. The voltage range of some high-voltage components is spread very widely, for example from 200 V to 800 V in a vehicle with a changeover battery instead of 400 V to 800 V in a vehicle without battery changeover. This necessitates additional measures in some high-voltage components or causes performance restrictions during charging on a DC charging column of at most 500 V.galvanically coupled boost converter. A disadvantage here is that the additional boost converter requires installation space and causes additional costs and additional weight. In the case of a galvanically coupled boost converter, the high-voltage potential distribution is transferred to a potential compensation / protective conductor (PA / PE) of the vehicle at the high-voltage potentials of the DC charging station. In the event of an asymmetry of the high-voltage potential distribution in the vehicle, this leads to an overload of the insulation in the DC charging column. Some charging station manufacturers install varistors for protecting the insulation between the high-voltage potentials and the potential compensation / protective conductor (PA / PE). In the event of an overvoltage, these varistors transition into a conductive state. An insulation fault in the vehicle can thus lead to a varistor in the charging column being switched on. The result is a battery short circuit via the PE cable of the DC charging column. In this case, the charging column, the cable and the vehicle are destroyed. In addition, during the short circuit, a voltage of more than 60 V can occur between the vehicle sheet and the housing of the charging station, so that persons can be endangered.galvanically coupled boosting via the inverter. The disadvantage here is that additional interference suppression measures and / or, if appropriate, an additional inductance are necessary. Further disadvantages correspond to the disadvantages of the galvanically coupled boost converter.galvanically isolated boost converters. A galvanically isolated DC / DC converter has a low power density and is thus substantially more expensive, heavier and larger than a galvanically coupled boost converter.The mechanical coupling of two electric machines has long been known (about >100 years). When power electronic components have not yet been available (e.g., transistors), it has been used to convert voltages or frequencies. Nowadays, such mechanical couplings are in use on test stands. A load machine is operated via a test stand inverter. This load machine is connected via a mechanical shaft to a test machine and a test inverter. Thus, different load points can be approached for characterizing the test inverter and the test machine (rotational speed and torque are varied). The load machine and the test stand inverter must be dimensioned to be stronger than the test-object inverter and the test-object machine in order to avoid uncontrolled runaway of the electrical machines. To reduce the energy consumption, both the test stand inverter and the test-object inverter are connected to a common energy source, so that only the power loss of both drives has to be supplied from the outside.DE 10 2020 007 249 A1 describes a vehicle having an electric drive system, comprising at least one electric energy store and at least two electric motor generators which are mechanically coupled or can be coupled to one another and each have at least one associated electric inverter, wherein the electric energy store is charged in a generator mode of the motor generators and at least one drive wheel is driven by motor in a motor mode of the motor generators. At least two independent electrical charging connections are provided.The object of the invention is to specify a novel vehicle having an electric drive system.The object is achieved according to the invention by a vehicle having an electric drive system having the features of claim 1.Advantageous embodiments of the invention are the subject matter of the dependent claims.A vehicle having an electric drive system is proposed, comprisingat least one high-voltage battery having a rated voltage,at least two electric machines which are mechanically coupled or can be coupled to one another and each have at least one associated electric inverter, the high-voltage battery being charged in a generator mode of the electric machines and at least one driven drive wheel being driven by a motor in a motor mode of the electric machines, anda charging connection, whereinat least one switching device for producing and disconnecting an electrical coupling is arranged between the charging connection and the high-voltage battery,a clutch for disconnecting a mechanical connection is arranged between the electric machines and the at least one drive wheel,a control device is provided which is designed to control charging of the high-voltage battery as a function of charging voltages present at the charging connection.According to the invention, a first high-voltage system to which the high-voltage battery and a first inverter are connected, and a second high-voltage system to which a second inverter is connected, are provided, wherein the switching device has charging contactors and isolating elements, wherein the second high-voltage system can be selectively coupled to the first high-voltage system via the isolating element or can be isolated therefrom. The second inverter is configured to operate at the rated voltage and at a lower voltage, wherein the controller is configured to charge the high voltage battery at a charging station at a maximum DC output voltage that is less than the rated voltage of the high voltage battery,connecting the second inverter to the charging connection via the charging contactors while the isolating element is open, so that the second inverter is supplied with electrical power by the charging station and drives the second electrical machine, which drives the first electrical machine via the mechanical connection,to rectify energy induced there via the first inverter and thus charge the high-voltage battery.The solution according to the invention enables charging (unidirectionally or bidirectionally) an electrically driven vehicle with a higher high-voltage on-board voltage, for example 800 V, at a charging column which provides a lower high-voltage, for example 500 V.The solution according to the invention enables the boost functionality to be presented (virtually) without additional components. In this case, the second inverter, but not the rest of the vehicle (first inverter, high-voltage system, high-voltage battery), is to be designed for load dump (load drop) during DC charging (10% more voltage during load shedding). There is no mutual influence on the high-voltage potential distribution by the vehicle system and by the system of the charging station. At the charging station, despite a weaker insulation design, no overloading of the insulation occurs in comparison with the vehicle. In the case of an insulation fault in the vehicle, no battery short circuit occurs as a direct consequence via an induced insulation fault in the charging station (chadeno short circuit). The value of the Y capacitance for the second inverter can be selected to be substantially higher, since only the charging station and the second inverter conform to the C1 characteristic curve. ISO 60479-2. This results in better and / or less expensive filtering to meet the EMC requirements for DC charging. Furthermore, heating functions are possible via the first inverter and / or the second inverter and the first and / or second electric machine during the DC charging (power waste). As a result, a high-voltage heater in the vehicle can be dispensed with.The present invention proposes, for voltage conversion in DC charging, using the mechanical connection between two electric machines. In this case, the voltage of the charging station is set in different ways at the second inverter. With such a system, when charging via the inverters, a DC charging voltage can be converted to the battery voltage without a DC / DC converter. If the charging voltage matches the battery voltage, then a direct DC connection is possible between charging connection and battery, which, however, can be disconnected via isolating elements if the voltage is not matched. In this case, according to the invention, the charging voltage and thus the charging power are (completely) converted and transmitted via the two inverters and the mechanical connection.Exemplary embodiments of the invention are explained in more detail below with reference to a drawing.The following shows: FIG. 1 shows a schematic view of an electrically driven vehicle having a high-voltage battery and two electric machines for driving the vehicle during charging at a DC voltage charging station.The single FIG. 1 is a schematic view of an electrically driven vehicle 1 having a high-voltage battery 2 and two electric machines 3.1, 3.2 for driving the vehicle 1 during charging at a DC voltage charging station 4.A first electric machine 3.1 can be supplied with energy from the high-voltage battery 2 via a first inverter 5.1. A second electric machine 3.2 can be supplied with energy from the high-voltage battery 2 via a second inverter 5.2. The high-voltage battery 2 has a rated voltage of 800 V, for example.The vehicle 1 has a first high-voltage system 8.1, to which the high-voltage battery 2 and the first inverter 5.1 are connected. The vehicle 1 further comprises a second high-voltage system 8.2, to which the second inverter 5.2 is connected, and which can be selectively coupled to the first high-voltage system 8.1 or disconnected therefrom. Furthermore, the second high-voltage system 8.2 can be coupled to a charging station 4 via charging contactors 9 and a charging connection 11. Electrical components connected to the second high-voltage system 8.2, in particular the second inverter 5.2, are configured for operation with the rated voltage of the high-voltage battery 2 and with a lower voltage, for example 400 V.The two electric machines 3.1, 3.2 can be coupled to one another via a mechanical connection 6, which can have a coupling 12, for example. Clutch 12 may be configured to disconnect a powertrain between electric machines 3.1, 3.2 and at least one drive wheel 13 of vehicle 1.If both electric machines 3.1, 3.2 rotate during charging, then a movement of the vehicle 1 must be ruled out. This is achieved by the clutch 12. The electric machines 3.1, 3.2 can be connected by a gear mechanism in order to enable different rotation of the electric machines 3.1, 3.2, for example in the same direction, in opposite directions and / or at different rotational speeds.The high-voltage battery 2 and both inverters 5.1, 5.2 are connected to high-voltage potentials HV+, HV20 on-board electrical system. At least one of the two high-voltage potentials HV+, HV- of the second inverter 5.2 in the second high-voltage system 8.2 can be disconnected from the first high-voltage system 8.1 via at least one galvanically isolating disconnection element 7, for example a contactor 7. Preferably, both high-voltage potentials HV+, HV- of the second inverter 5.2 of the second high-voltage system 8.2 can be separated from the first high-voltage system 8.1 via a galvanically isolating separator element 7, for example a contactor 7 in each case, in order to achieve a galvanic isolation of the first high-voltage system 8.1 and the second high-voltage system 8.1.For the DC charging operation of the vehicle 1 at a charging station 4 with a lower maximum DC output voltage (e.g. 500 V) than the rated voltage of the high-voltage battery 2, the second inverter 5.2 is connected to the charging connection 11 via the charging contactors 9 or changeover switches, while the isolating elements 7 between the first high-voltage system 8.1 and the second high-voltage system 8.2 are open. Thus, this second inverter 5.2 is directly connected to the charging station 4 (EVSE) and is supplied with electrical power by it. The second inverter 5.2 thus drives the associated second electric machine 3.2 (for example commanded via a control device of the vehicle 1). The rotation of the second electric machine 3.2 causes the first electric machine 3.1 to rotate via the mechanical connection 6. The energy induced there is rectified via the first inverter 5.1, the high-voltage battery 2 can thus be charged and the first high-voltage system 8.1 can be supplied with energy during the DC charging process. A working point with regard to rotational speed and torque can be selected here, for example, such that the efficiency of both electric machines 3.1, 3.2 assumes a maximum value and / or that the power to be transmitted assumes a maximum and / or that the generated noises of the rotating electric machines 3.1, 3.2 are minimized and / or that generated electromagnetic interference at the charging connection 11 are minimized.During the travel of the vehicle 1, the separators 7 are closed in order to supply both inverters 5.1, 5.2 from the high-voltage battery 2. Further, the separators 7 are closed during charging at a charging station 4 whose voltage corresponds to or higher than the rated voltage of the high-voltage battery 2 (for example, 800 V). During DC charging at a charging station 4 with less than the rated voltage of the high-voltage battery 2 (e.g. 500 V, boost function), the isolating elements 7 are open.The charging station 4 starts the charging operation when a DC voltage applied from the outside at its DC charging terminal corresponds to an internal voltage of the charging station 4. In the normal case, the voltage applied from the outside corresponds to the rated voltage of the high-voltage battery 2 of the connected vehicle 1. This established sequence assumes that the voltage of the charging station 4 can always be selected to be equal to or greater than the rated voltage of the high-voltage battery 2 of the vehicle 1. Since the high-voltage battery 2 is disconnected via the isolating elements 7 during charging at a charging station 4 with less than the rated voltage of the high-voltage battery 2, only one voltage of an intermediate circuit capacitor 10 of the second inverter 5.2 is visible to the charging station 4. This intermediate circuit capacitor 10 must therefore be precharged, before the start of the charging process within the vehicle 1, to the value which is predefined by the vehicle 1 for the charging station 4, for example 400 V.This can be effected in the following manner: 1. the intermediate circuit capacitor 10 is completely discharged and then charged to the starting voltage value of the DC charging process (e.g. 400 V). The separating elements 7 are then opened and the charging contactors 9 are closed. Subsequently, the intermediate circuit capacitor 10 is further charged to the voltage of the high-voltage battery 2 (e.g. 800 V). 2. the intermediate circuit capacitor 10 is completely charged to the voltage of the high-voltage battery 2 (e.g. 800 V). The separators 7 are then opened to the second inverter 5.2. The voltage is lowered via the passive or active discharge of the intermediate circuit capacitor 10 of the second inverter 5.2. If the value predetermined by the vehicle 1 for the charging station 4 is reached, the charging contactors 9 are closed. 3. the intermediate circuit capacitor 10 is completely discharged. The separators 7 are then opened to the second inverter 5.2. The intermediate circuit capacitor 10 is now fully charged to the voltage of the high-voltage battery 2. The first inverter 5.1 now sets the first electric machine 3.1 in a rotational movement, so that a voltage is induced via the electric machine 3.2 which likewise rotates in the process, which voltage charges the intermediate circuit capacitor 10 to the predefined value (e.g. 400 V) via the second inverter 5.2.List of reference characters1 Vehicle 2 High-voltage battery 3.1, 3.2 Electric machine 4 Direct-voltage charging station, charging station 5.1, 5.2 Inverter 6 Mechanical connection 7 Separating element, contactor 8.1, 8.2 High-voltage system 9 Charging contactor 10 Intermediate circuit capacitor 11 Charging connection 12 Clutch 13 Drive wheel HV+, HV-High-voltage potentialReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2020 007 249 A1

[0005]

Claims

Vehicle (1) with an electric drive system, comprising - at least one high-voltage battery (2) with a rated voltage, - at least two electric machines (3.1, 3.2) which are mechanically coupled or can be coupled to one another and each have at least one associated electric inverter (5.1, 5.2), wherein in a generator mode of the electric machines (3.1, 3.2) the high-voltage battery (2) is charged and in a motor mode of the electric machines (3.1, 3.2) at least one driven drive wheel (13) is driven by a motor, and - a charging connection (11), wherein - at least one switching device for producing and disconnecting an electric coupling is arranged between the charging connection (11) and the high-voltage battery (2), - a clutch (12) for disconnecting a mechanical connection is arranged between the electric machines (3.1, 3.2) and the at least one drive wheel (13), - a control device is provided, A high-voltage battery (2) which is designed to control charging of the high-voltage battery (2) as a function of charging voltages present at the charging connection (11), characterized bya first high-voltage system (8.1) to which the high-voltage battery (2) and a first inverter (5.1) are connected, a second high-voltage system (8.2) to which a second inverter (5.2) is connected, wherein the switching device has charging contactors (9) and at least one isolating element (7), wherein the second high-voltage system (8.2) can be selectively coupled to the first high-voltage system (8.1) via the isolating element (7) or disconnected therefrom, wherein the second inverter (5.2) is configured for operation at the rated voltage and at a lower voltage, wherein the control device is configured for the purpose of being able to switch on, for charging the high-voltage battery (2) at a charging station (4) with a maximum DC output voltage which is lower than the rated voltage of the high-voltage battery (2), - connecting the second inverter (5.2) via the charging contactors (9) to the charging connection (11), while the isolating element (7) is open, such that the second inverter (5.2) is supplied with electrical power by the charging station (4) and drives the second electrical machine (3.2), which drives the first electrical machine (3.1) via the mechanical connection (6), - rectifying energy induced there via the first inverter (5.1) and charging the high-voltage battery (2) therewith.Vehicle (1) according to Claim 1, characterized in that the control device is configured to close the isolating elements (7) during the journey of the vehicle (1) and / or during charging at a charging station (4) whose voltage corresponds to the rated voltage of the high-voltage battery (2) or is higher.Vehicle (1) according to Claim 1 or 2, characterized in that the control device is configured to pre-charge an intermediate circuit capacitor (10) of the second inverter (5.2) before the start of a charging process to a value which is predetermined by the vehicle (1) to the charging station (4) or which corresponds to the maximum DC output voltage of the charging station (4), wherein the control device is configured to: - discharge the intermediate circuit capacitor (10) and then charge it to a starting voltage value of the DC charging process, then open the separating elements (7) and close the charging contactors (9) and then charge the intermediate circuit capacitor (10) further to the voltage of the high-voltage battery (2), or - charge the intermediate circuit capacitor (10) to the voltage of the high-voltage battery (2), subsequently, opening the separating elements (7) to the second inverter (5.2), lowering the voltage of the intermediate circuit capacitor (10) via passive or active discharge of the intermediate circuit capacitor (10) and closing the charging contactors (9) when the value predefined for the charging station (4) by the vehicle (1) or the maximum DC output voltage of the charging station (4) is reached in the process, - discharging the intermediate circuit capacitor (10), subsequently opening the separating elements (7), charging the intermediate circuit capacitor (10) to the voltage of the high-voltage battery (2), controlling the first inverter (5.1) for a rotation of the first electric machine (3.1), so that a voltage is induced via the electric machine (3.2) which likewise rotates in the process, which voltage charges the intermediate circuit capacitor (10) to the predefined value via the second inverter (5.2).Vehicle (1) according to one of the preceding claims, characterized in that the electric machines (3.1, 3.2) are connected by a transmission in order to enable different rotation of the electric machines (3.1, 3.2), in particular in the same direction, in opposite directions and / or at different rotational speeds.Vehicle (1) according to one of the preceding claims, characterized in that both high-voltage potentials (HV+, HV-) of the second high-voltage system (8.2) can be separated from the first high-voltage system (8.1) via in each case one galvanically separating element (7).Vehicle (1) according to one of the preceding claims, characterized in that the control device is configured to select an operating point with respect to rotational speed and torque during charging via the two inverters (5.1, 5.2) and electric machines (3.1, 3.2) such that the efficiency of both electric machines (3.1, 3.2) assumes a maximum value and / or that the power to be transmitted assumes a maximum and / or that noise generated by the rotating electric machines (3.1, 3.2) is minimized and / or that electromagnetic interference generated at the charging connection (11) is minimized.

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