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 connection (11), wherein a first of two high-voltage potentials (HV+, HV-) of the charging connection (11) can be separated from or connected to the high-voltage battery (2) via a first separating element (7.1), wherein a second separating element (7.2) is arranged to selectively connect or separate the other high-voltage potential (HV-, HV+) on the first inverter (5.1) from the same-pole high-voltage potential (HV-, HV+) on the second inverter (5.2) and on the high-voltage battery (2), wherein a third separating element (7.3) is arranged to selectively connect or separate the other high-voltage potential (HV-, HV+) on the first inverter (5.1) from the first high-voltage potential (HV+, HV-) on the second inverter (5.2), wherein a control device is configured to charge 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 open the first and second separating elements (7.1, 7.2) and to close the third separating element (7.3) in order to connect the first inverter (5.1) in series with the charging terminal (11).

Description

[0001] The invention relates to a vehicle with an electric drive system according to the preamble of claim 1.

[0002] For an electric vehicle with a voltage level of, for example, 800 V, it is only possible to charge at DC charging stations whose maximum output voltage is equal to or higher than the final DC charging voltage. However, some (older) DC charging stations only provide a maximum DC voltage of 500 V, so the vehicle cannot be charged there.

[0003] So far, this problem has been solved by the following measures, for example: - Switchable battery (switching between series and parallel battery strings or alternating charging of battery strings). The disadvantage of this is that additional contactors and busbars are required in the battery. This incurs additional costs and limits the space available for battery cells. The voltage range of some high-voltage components is very wide, e.g., from 200 V to 800 V for a vehicle with a switchable battery instead of 400 V to 800 V for a vehicle without a switchable battery. This requires additional measures in some high-voltage components or results in power limitations when charging at a DC charging station with a maximum of 500 V. - Galvanically coupled boost converter. The disadvantage is that the additional boost converter requires installation space and causes additional costs and weight. With a galvanically coupled boost converter, the high-voltage potential distribution to the vehicle's equipotential bonding / protective conductor (PA / PE) is transferred to the high-voltage potentials of the DC charging station. If the high-voltage potential distribution in the vehicle is asymmetry, this leads to an overload of the insulation in the DC charging station. Some charging station manufacturers install varistors to protect the insulation between the high-voltage potentials and the equipotential bonding / protective conductor (PA / PE). In the event of an overvoltage, these varistors become conductive. An insulation fault in the vehicle can thus cause a varistor in the charging station to switch through. The result is a battery short circuit via the PE cable of the DC charging station. This destroys the charging station, the cable, and the vehicle.In addition, a voltage of more than 60 V can occur between the vehicle's sheet metal and the charging station housing during the short circuit, which could endanger people. - Galvanically coupled boosting via the inverter. The disadvantage is that additional interference suppression measures and / or possibly an additional inductance are required. Other disadvantages correspond to those of the galvanically coupled boost converter. - Galvanically isolated boost converter. A galvanically isolated DC / DC converter has a low power density and is therefore significantly more expensive, heavier, and larger than a galvanically coupled boost converter.

[0004] The mechanical coupling of two electrical machines has been known for a very long time (approximately > 100 years). When power electronic components (e.g., transistors) were not yet available, it was used to convert voltages or frequencies. Today, such mechanical couplings are used on test benches. A load machine is operated via a test bench inverter. This load machine is connected to a test machine and a test inverter via a mechanical shaft. This allows different load points to be approached (speed and torque are varied) to characterize the test inverter and the test machine. The load machine and the test bench inverter must be dimensioned more powerful than the test inverter and the test machine to prevent uncontrolled runaway of the electrical machines.To reduce energy consumption, both the test bench inverter and the test object inverter are connected to a common energy source so that only the power loss of both drives needs to be supplied from the outside.

[0005] DE 10 2020 007 249 A1 describes a vehicle with an electric drive system, comprising at least one electrical energy storage device and at least two electrical motor generators that are mechanically coupled or can be coupled to one another, each with at least one associated electrical inverter. Charging of the electrical energy storage device occurs during generator operation of the motor generators, and motor drive of at least one drive wheel occurs during motor operation of the motor generators. At least two independent electrical charging connections are provided.

[0006] The invention is based on the object of providing a novel vehicle with an electric drive system.

[0007] The object is achieved according to the invention by a vehicle with an electric drive system having the features of claim 1.

[0008] Advantageous embodiments of the invention are the subject of the subclaims.

[0009] A vehicle with an electric drive system is proposed, comprising - at least one high-voltage battery with a nominal voltage, - at least two electrical machines which are mechanically coupled or can be coupled to one another, each having at least one associated electrical inverter, wherein in generator mode of the electrical machines the high-voltage battery is charged and in motor mode of the electrical machines a motor drive of at least one driven drive wheel is provided, and - a charging port, where - at least one switching device for establishing and separating an electrical connection is arranged between the charging connection and the high-voltage battery, - a clutch for separating a mechanical connection is arranged between the electrical 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 applied to the charging connection.

[0010] According to the invention, the switching device comprises charging contactors and isolating elements, wherein a first of two high-voltage potentials of the charging connection can be disconnected from or connected to the high-voltage battery via a first isolating element, wherein a second isolating element is arranged to selectively connect or disconnect the other high-voltage potential at the first inverter to the same-pole high-voltage potential at the second inverter and at the high-voltage battery, wherein a third isolating element is arranged to selectively connect or disconnect the other high-voltage potential at the first inverter to the first high-voltage potential at the second inverter. The second inverter is configured for operation with the nominal voltage and with a lower voltage. The control device is configured for charging the high-voltage battery at a charging station with a maximum DC output voltage that is lower than the nominal voltage of the high-voltage battery, - open the first and second isolating elements and close the third isolating element to connect the first inverter in series with the charging terminal, - to connect the second inverter to the charging port via the charging contactors, 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 the energy induced there via the first inverter and to charge the high-voltage battery with voltage from the series connection of the first inverter with the charging station.

[0011] The solution according to the invention enables the charging (unidirectional or bidirectional) of an electrically powered vehicle with a higher high-voltage on-board voltage, for example 800 V, at a charging station that provides a lower high-voltage voltage, for example 500 V.

[0012] The inventive solution enables the implementation of the boost functionality (almost) without additional components. Furthermore, a heating function is possible via the first inverter and / or the second inverter and the first and / or second electric machine during DC charging (power waste). This eliminates the need for a high-voltage heater in the vehicle. Only a portion of the DC charging power needs to be boosted via the inverters.

[0013] Embodiments of the invention are explained in more detail below with reference to drawings.

[0014] Showing: Fig. 1 a schematic view of an electrically powered vehicle with a high-voltage battery and two electric motors for driving the vehicle when charging at a DC charging station and Fig. 2 another schematic view of the electrically powered vehicle during charging at a DC charging station.

[0015] Corresponding parts are provided with the same reference numerals in all figures.

[0016] Fig. 1 is a schematic view of an electrically powered vehicle 1 with a high-voltage battery 2 and two electric machines 3.1, 3.2 for driving the vehicle 1 during charging at a DC charging station 4.

[0017] 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 nominal voltage of, for example, 800 V.

[0018] The vehicle 1 has a first high-voltage electrical system 8, to which the high-voltage battery 2, the first inverter 5.1, and the second inverter 5.2 are connected. Furthermore, the high-voltage electrical system 8 can be coupled to a charging station 4 via charging contactors 9 and a charging connection 11. The second inverter 5.2 is configured for operation with the nominal voltage of the high-voltage battery 2 and with a lower voltage, for example, 400 V.

[0019] The two electric machines 3.1, 3.2 can be coupled to one another via a mechanical connection 6, which may, for example, comprise a clutch 12. The clutch 12 can be configured to disconnect a drive train between the electric machines 3.1, 3.2 and at least one drive wheel 13 of the vehicle 1.

[0020] When the two electric motors 3.1, 3.2 rotate during charging, any movement of the vehicle must be prevented. This is achieved by the coupling 12. The electric motors 3.1, 3.2 can be connected by a gear to enable different rotation of the electric motors 3.1, 3.2, for example, in the same direction, in opposite directions, and / or at different rotation speeds.

[0021] The high-voltage battery 2 and both inverters 5.1, 5.2 are connected to high-voltage potentials HV+, HV of an on-board electrical system 8. One of the two high-voltage potentials HV+, HV- of the second inverter 5.2, for example a positive high-voltage potential HV+, can be separated from or connected to the high-voltage battery 2 and other high-voltage components 15 via a galvanically isolating first isolating element 7.1, for example a first contactor 7.1. A galvanically isolating second isolating element 7.2, for example a second contactor 7.2, is arranged to selectively connect or separate the negative high-voltage potential HV- at the first inverter 5.1 from the negative high-voltage potential HV- at the second inverter 5.2 and at the high-voltage battery 2. A galvanically isolating third isolating element 7.3, for example a third contactor 7.3, is arranged to connect a negative high-voltage potential HV- on the first inverter 5.1 optionally with the positive high-voltage potential HV+ on the second inverter 5.2 to connect or disconnect.

[0022] For DC charging of the vehicle 1 at a charging station 4 with a lower maximum DC output voltage (e.g., 500 V) than the nominal voltage of the high-voltage battery 2, the second inverter 5.2 is connected to the charging port 11 via the charging contactors 9 or changeover switches, while the first and second isolating elements 7.1, 7.2 are open and the third isolating element 7.3 is closed. Thus, this second inverter 5.2 is directly connected to the charging station 4 (EVSE) and is supplied with electrical power by it, while the high-voltage battery 2 is connected to a series circuit comprising the first inverter 5.1 and the charging station 4. One of the high-voltage potentials HV+, HV- of the charging station 4 (in the illustrated embodiment, the negative high-voltage potential HV-) is connected directly to the high-voltage battery 2 and the second inverter 5.2 via the charging contactor 9. The second inverter 5.2 drives (for example, commanded via a control unit of the vehicle 1) the associated second electric machine 3.2. The rotation of the second electric machine 3.2 causes the first electric machine 3.1 to rotate via the mechanical connection 6. The voltage induced there is rectified via the first inverter 5.1. The first inverter 5.1 is, as described above, connected in series with the voltage of the charging station 4. Therefore, the voltages of the charging station 4 and the first inverter 5.1 add up to a value suitable for charging the high-voltage battery 2. The high-voltage battery 2 can thus be charged, and the high-voltage components 15 can be supplied with energy during the DC charging process.

[0023] The energy transfer is possible bidirectionally, i.e. the vehicle 1 can be charged or energy from the high-voltage battery 2 of the vehicle 1 can be fed into the infrastructure.

[0024] An operating point with regard to speed and torque can, for example, be selected such that the efficiency of both electrical machines 3.1, 3.2 assumes a maximum value and / or that the power to be transmitted assumes a maximum and / or that the noise generated by the rotating electrical machines 3.1, 3.2 is minimized and / or that electromagnetic interference generated at the charging connection 11 is minimized.

[0025] When charging at a charging station 4 with a voltage equal to or higher than the nominal voltage of the high-voltage battery 2, the charging contactors 9 and the first separator 7.1 are closed, and the third separator 7.3 is opened. The position of the second separator 7.2 is irrelevant. The energy transfer from the charging station 4 to the high-voltage battery 2 occurs bypassing the inverters 5.1, 5.2.

[0026] When the vehicle 1 is moving, the first and second separating elements 7.1, 7.2 are closed, the third separating element 7.3 and the loading gates 9 are open.

[0027] Fig. Figure 2 is another schematic view of the electrically powered vehicle 1 during charging at a DC charging station 4 with a voltage that is lower than the nominal voltage of the high-voltage battery 2. The isolating elements 7.1 to 7.3 are not shown here. The second inverter 5.2 and thus the second electric machine 3.2 are supplied directly from the charging station 4. A current I1 flows. The first electric machine 3.1 is driven by the second electric machine 3.2 and acts as a generator. The voltage induced in this process is rectified by the first inverter 5.1 and connected in series with the voltage of the charging station 4, i.e., both voltages add up and are, in total, slightly greater than the nominal voltage of the high-voltage battery 2, so that the high-voltage battery 2 can be charged. A current I2 flows from the charging station 4 via the first inverter 5.1 and the high-voltage battery 2 back to the charging station 4.For example, the currents I1 and I2 are equal in order to obtain a temporally constant voltage distribution between the charging station 4 and the inverters 5.1, 5.2.

[0028] To achieve 100% DC charging power, only 50% of the power needs to be transferred via inverters 5.1, 5.2 and electric motors 3.1, 3.2 (this is where efficiency losses occur). 50% of the charging power comes directly from charging station 4 and is therefore loss-free. This improves charging efficiency and increases charging power.

[0029] The charging station 4 begins the charging process when an externally applied DC voltage at its DC charging connection corresponds to an internal voltage of the charging station 4. Normally, the externally applied voltage corresponds to the nominal voltage of the high-voltage battery 2 of the connected vehicle 1. The internal voltage corresponds to a value that was previously specified to the charging station 4 by the vehicle 1. This established process assumes that the voltage of the charging station 4 can always be selected to be equal to or greater than the nominal voltage of the high-voltage battery 2 of the vehicle 1. Since the high-voltage battery 2 is separated via the first separating element 7.1 when charging at a charging station 4 with less than the nominal voltage of the high-voltage battery 2, only a voltage of an intermediate circuit capacitor 10 (shown in Fig.1) of the second inverter 5.2. This intermediate circuit capacitor 10 must therefore be precharged within vehicle 1 to the value specified by vehicle 1 to the charging station 4, for example, 400 V, before the charging process begins.

[0030] This can be done in the following ways: In an initial state, the isolating elements 7.1 to 7.3 and the charging contactors 9 are in their position for driving the vehicle, i.e., the first and second isolating elements 7.1, 7.2 are closed, and the third isolating element 7.3 and the charging contactors 9 are open. The intermediate circuit capacitors 10 of the two inverters 5.1, 5.2 are completely discharged and then charged to the starting value of the DC charging process (e.g., 400 V). This charges the intermediate circuit capacitors 10 of the two inverters 5.1, 5.2 to the same voltage. In this case, this must correspond to half the nominal voltage of the high-voltage battery 2. This value is also specified for the charging station 4. Subsequently, the first and second isolating elements 7.1, 7.2 are opened, followed by the third isolating element 7.3 and finally the charging contactors 9 are closed. The charging process can thus begin. List of reference symbols 1 vehicle 2 high-voltage batteries 3.1, 3.2 electrical machine 4 DC charging station, charging station 5.1, 5.2 Inverter 6 mechanical connection 7.1, 7.2, 7.3 Isolating element, contactor 8 High-voltage electrical system 9 Charging contactor 10 DC link capacitor 11 Charging port 12 Clutch 13 Drive wheel 15 high-voltage components HV+, HV- high-voltage potential 11, I2 current QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2020 007 249 A1

[0005]

Claims

[1] Vehicle (1) with an electric drive system, comprising - at least one high-voltage battery (2) with a nominal voltage, - 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), wherein in a generator mode of the electrical machines (3.1, 3.2) the high-voltage battery (2) is charged and in a motor mode of the electrical machines (3.1, 3.2) at least one driven drive wheel (13) is driven by a motor, and - a charging port (11), wherein - at least one switching device for establishing and separating an electrical connection is arranged between the charging connection (11) and the high-voltage battery (2), - a clutch (12) for separating a mechanical connection is arranged between the electrical machines (3.1, 3.2) and the at least one drive wheel (13), - a control device is provided which is designed to control charging of the high-voltage battery (2) as a function of charging voltages applied to the charging connection (11), characterized bythat the switching device has charging contactors (9) and isolating elements (7.1 to 7.3), wherein a first of two high-voltage potentials (HV+, HV-) of the charging connection (11) can be separated from or connected to the high-voltage battery (2) via a first isolating element (7.1), wherein a second isolating element (7.2) is arranged to selectively connect or separate the other high-voltage potential (HV-, HV+) on the first inverter (5.1) from the same-pole high-voltage potential (HV-, HV+) on the second inverter (5.2) and on the high-voltage battery (2), wherein a third isolating element (7.3) is arranged to selectively connect or separate the other high-voltage potential (HV-, HV+) on the first inverter (5.1) from the first high-voltage potential (HV+, HV-) on the second inverter (5.2), wherein the second inverter (5.2) is configured to operate at the nominal voltage and at a lower voltage, wherein the control device is configured to charge the high-voltage battery (2) at a charging station (4) with a maximum DC output voltage which is lower than the nominal voltage of the high-voltage battery (2). - to open the first and second separating elements (7.1, 7.2) and to close the third separating element (7.3) in order to connect the first inverter (5.1) in series with the charging connection (11), - to connect the second inverter (5.2) to the charging connection (11) via the charging contactors (9) 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 voltage from the series connection of the first inverter (5.1) with the charging station (4). [2] Vehicle (1) according to claim 1, characterized by that the control device is configured to close the charging contactors (9) and the first isolating element (7.1) and to open the third isolating element (7.3) when charging at a charging station (4) with a voltage which corresponds to or is higher than the nominal voltage of the high-voltage battery (2), to close the first and second isolating elements (7.1, 7.2) and to open the third isolating element (7.3) and the charging contactors (9) when driving the vehicle (1). [3] Vehicle (1) according to claim 1 or 2, characterized bythat the control device is configured to precharge intermediate circuit capacitors (10) of the inverters (5.1, 5.2) before the start of a charging process to a value that is specified to the charging station (4) by the vehicle (1) or that corresponds to the maximum DC output voltage of the charging station (4), 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 completely discharge the intermediate circuit capacitors (10) of the two inverters (5.1, 5.2) and then to charge them to the starting value of the DC charging process and to specify this starting value to the charging station (4), then to open the first and second isolating elements (7.1, 7.2), then to close the third isolating element (7.3) and finally to close the charging contactors (9). [4] Vehicle (1) according to one of the preceding claims, characterized bythat the electrical machines (3.1, 3.2) are connected by a gear to enable different rotation of the electrical machines (3.1, 3.2), in particular in the same direction, in opposite directions and / or at different rotation speeds. [5] Vehicle (1) according to one of the preceding claims, characterized by that the control device is configured to select an operating point with regard to speed and torque when charging via the two inverters (5.1, 5.2) and electrical machines (3.1, 3.2) such that the efficiency of both electrical 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 electrical machines (3.1, 3.2) is minimized and / or that electromagnetic interference generated at the charging connection (11) is minimized.

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