Electric drive system for a vehicle and method of operating an electric drive system

Abstract

The present invention relates to an electric drive system (1) for a vehicle, the electric drive system for a vehicle comprising: a first three-phase electric machine (5) and a second three-phase electric machine (6) for driving at least one drive axle (4) of a vehicle; an electric energy store (2) for supplying electricity to a first and a second three-phase electric machine (5, 6) during driving operation of the vehicle, a first inverter (9) of the first three-phase electric machine (5) and a second inverter (10) of the second three-phase electric machine (6) being respectively coupled to the electric energy store (2); - a vehicle-side charging terminal (3) for electrically connecting the electric energy storage device (2) to a charging unit (11) external to the vehicle, The first and / or second inverter (9, 10) is capable of converting the charging voltage (UL) at the vehicle-side charging terminal (3) into a supply voltage (UV) for charging the electric energy store (2). Furthermore, the present invention relates to a method.

Description

[Technical Field]

[0001] The present invention relates to an electric drive system for a vehicle according to the preamble of claim 1. Furthermore, the present invention relates to a method for operating an electric drive system according to the preamble of claim 5. [Background technology]

[0002] Electrically powered vehicles currently have a voltage level of 800 volts, which means that these vehicles are equipped with an 800 volt vehicle battery that can be used to provide energy to the on-board electrical system and / or the electric drive machine. For example, this is disclosed in Patent Document 1 and Patent Document 2. An AC voltage is required for the electric machine of a vehicle to be able to drive the vehicle. This AC voltage is generated from the battery voltage of the on-board battery using an inverter. For example, this is disclosed in Patent Document 3.

[0003] US Pat. No. 5,623,999 and US Pat. No. 5,623,999 each disclose a switching assembly for an automotive vehicle, where an electric machine of the vehicle is supplied with electrical energy by a power converter via the vehicle's high voltage battery. The drawback of charging an 800-volt vehicle with a 400-volt charging column is the high additional cost for backward compatibility. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] DE102019005621A1 [Patent Document 2] DE102009052680A1 [Patent Document 3] DE102018000488A1 [Patent Document 4] DE102018009848A1 [Patent Document 5] DE102018009840A1 Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION The object of the present invention is to make it possible to charge the electric energy store of an at least partly electrically operated vehicle more easily and independently of the voltage level of the charging station. [Means for solving the problem]

[0006] The above object is achieved by an electric drive system and method according to the independent claims. Significant developments emerge from the dependent claims.

[0007] An aspect of the present invention relates to an electric drive system for a vehicle, the electric drive system comprising: - a first three-phase electric machine and a second three-phase electric machine for driving at least one drive axle of a vehicle; an electric energy storage for supplying electricity to first and second three-phase electric machines during running operation of the vehicle, wherein a first inverter of the first three-phase electric machine and a second inverter of the second three-phase electric machine are respectively coupled to the electric energy storage; a vehicle-side charging terminal for electrically coupling the electric energy storage device to a charging unit external to the vehicle; The first and / or second inverter can convert the charging voltage at the vehicle-side charging terminal into a supply voltage for charging the electric energy storage.

[0008] By using two inverters in the proposed electric drive system, an electric vehicle with a voltage level of 800 volts can be efficiently and easily charged at a charging station with a 400 volt or 500 volt voltage. As a result, the proposed electric drive system can be used to improve the backward compatibility of electric vehicles, allowing an electric vehicle with a battery voltage of 800 volts to be charged at a 400 volt charging column. By using two inverters in a three-phase electric machine, an additional voltage converter or other circuit assembly for charging at a 400 volt charging column can be omitted. Therefore, the proposed electric drive system can be used to efficiently and easily charge an electrically powered vehicle even when the charging station's voltage level is lower than the battery voltage. This backward compatibility results in weight and cost savings by eliminating additional switching configurations.

[0009] In other words, the electric drive system of a vehicle, particularly an at least partially electrically driven vehicle, can have two electric drive machines or three-phase electric machines per drive axle. In particular, two electric machines can be arranged per drive axle of the vehicle. Therefore, in particular, each wheel of the vehicle, in particular each axle of the vehicle, can be individually driven and controlled by its own electric machine. This, on the other hand, offers the additional advantage that a mechanical differential can be omitted and replaced with an electric differential provided by an electric machine. This can, in particular, achieve weight and cost savings for the vehicle. One advantage of using multiple electric machines per drive axle is the implementation of "torque vectoring."

[0010] In other words, for example, two drive inverters of the vehicle's axles are used for the charging process in addition to their intended purpose, thus realizing the primary function of supplying electricity to a three-phase electric machine and the secondary function of allowing the charging of an electric energy storage device at a charging station with a voltage level lower than that of the vehicle.

[0011] Furthermore, the inductance of the three-phase electric machine can be utilized for the charging process at the charging station, so that additional space is not required for installing large and heavy chokes to increase the relatively low voltage of the charging station. By using two three-phase electric drive machines for charging with a direct current charging source, EMC interference or electromagnetic disturbances in the direction of the direct current charging source (DC charging socket) can be kept low, and the EMC filter required in the direction of the DC charging socket can be designed smaller and more inexpensively. EMC filters are usually used to protect the charging column from disturbances or fluctuations. By using two inverters of three-phase machines, especially the inductance of the three-phase machines, such EMC filters can be omitted, which further reduces costs and weight.

[0012] It is particularly advantageous if one of the two inverters is used when charging from a 400-volt charging column, while the other inverter switches the required current path, particularly in a clocked manner. This allows at least one inverter to be used as a step-up converter to boost the 400 volts of the charging column to the 800 volts of the vehicle battery. This also allows the inverter already installed in the vehicle to be used for a different purpose, thereby eliminating the need for additional components for backward compatibility with the 400-volt charging process. As a result, the inverter of the electric drive system has the additional function of charging from a 400-volt charging column in addition to its primary function, thereby eliminating the need for additional components.

[0013] Another aspect of the invention relates to a method of operating an electric drive system of a vehicle, the method comprising: - during operation of the vehicle, at least one drive shaft of the vehicle is driven by the first three-phase electric machine and the second three-phase electric machine; a first inverter of the first three-phase machine and a second inverter of the second three-phase machine are each supplied with electricity by an electrical energy storage; - for a charging operation of the vehicle, vehicle-side charging terminals of the vehicle are electrically coupled to the first and second three-phase electric machines; and The first and second inverters convert the charging voltage at the vehicle-side charging terminal into a supply voltage for charging the electric energy storage.

[0014] The proposed method allows the electric drive system, in addition to its primary function of driving a vehicle using a three-phase electric machine, to be used for vehicle charging operations in an off-the-shelf manner, whereby the electric drive system has the function of supplying a three-phase electric machine for driving a vehicle and the secondary function of charging an 800 volt vehicle at a 400 volt charging station.

[0015] In particular, the method just described can be carried out using an electric drive system according to the above-described aspects or advantageous embodiments thereof.

[0016] Advantageous embodiments of the electric drive system can be considered as advantageous embodiments of the method, to which end the electric drive system has specific features that enable the execution of the method or advantageous embodiments thereof.

[0017] In particular, advantageous embodiments of one aspect should be considered as advantageous embodiments of the other aspect, and vice versa.

[0018] Further advantages, features and details of the invention will become apparent from the following description based on preferred embodiments and on one or more of the drawings. The features and combinations of features mentioned in the above description and in the following description of the figures and / or shown only in the figures can be used not only in the respective combinations presented, but also in other combinations or alone without departing from the scope of the invention. [Brief explanation of the drawings]

[0019] [Figure 1]FIG. 1 is a schematic block diagram of a vehicle's drive system in an 800V charging process of the vehicle. [Figure 2] FIG. 2 is another schematic block diagram of the drive system of FIG. 1 during a 400V charging process of the vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0020] In the drawings, functionally identical elements are designated by the same reference numerals.

[0021] 1 shows a schematic diagram of an electric drive system 1 of a vehicle according to the invention, for example. This is the electric drive system of an electric or hybrid vehicle. For example, the voltage level of the vehicle is 800 volts. At this voltage level, the voltage is in particular the battery voltage U of the electric energy store 2 of the vehicle. Batt In this case, the battery voltage U of the electrical energy storage device 2 Batt has a voltage range of 770 to 830 volts. In particular, the battery voltage U Batt may vary depending on the state of charge of the electric energy storage device 2 and / or the circuit configuration of the electric drive system 1 and / or the operating state of the electric drive system 1. In particular, the electric energy storage device may be configured to generate a battery voltage U of substantially 800 volts. Batt It has.

[0022] In the present application, "substantially" is to be understood as a tolerance of + / - 5 percent, in particular + / - 10 percent. In particular, when voltage values ​​are stated, a tolerance of 5%, in particular 10%, and / or a measurement tolerance must be taken into account.

[0023] In particular, the electric drive system 1 should be understood as all components and / or systems necessary to drive or move a vehicle. In particular, the electric drive system 1 includes a vehicle frame, an electric energy storage device 2, a vehicle-side charging terminal 3, at least one drive shaft 4, , andand at least a first three-phase electric machine 5 and a second three-phase electric machine 6. The electric drive system 1 can thus be used to perform locomotion of the vehicle.

[0024] In particular, the electric drive system 1 has at least one drive shaft 4, which is in particular an shaft driven by a three-phase electric machine 5, 6. In particular, the vehicle or the electric drive system 1 can have several drive shafts. In particular, the vehicle can be a passenger car with one or two drive shafts or a goods vehicle with several drive shafts.

[0025] In particular, this at least one drive axle 4 has two three-phase electric machines 5, 6. Thus, each drive axle of the vehicle can have at least two three-phase electric machines. In other words, for example, each wheel of a drive axle can be driven by its own electric machine, i.e., two three-phase machines 5, 6. In particular, each tire of the vehicle can be driven or controlled by its own electric drive machine.

[0026] For example, the first three-phase electric machine 5 and the second three-phase electric machine 6 can be arranged together or together on the rear or front axle as the drive axle. Thus, for example, two three-phase electric machines can be arranged per axle. For example, both the rear and front axles can have two three-phase machines. In particular, the two three-phase machines 5, 6 are arranged on either the rear or front axle depending on whether the drive axle of the vehicle is the rear or front axle. In that case, for example, the first wheel 7 of the drive axle 4 can be driven by the first three-phase machine 5, and the second wheel 8, different from the first wheel 7 of the drive axle 4, can be driven by the second three-phase electric machine 6.

[0027] To enable the two three-phase electric machines 5, 6 to drive the drive shaft 4, these three-phase electric machines are supplied or fed with energy by an electric energy store 2. The battery voltage U Battis a DC voltage, while the three-phase electric machines 5, 6 require an AC voltage, so the three-phase electric machines 5, 6 have inverters 9, 10, respectively. The first three-phase electric machine 5 has a first inverter 9, and the second three-phase electric machine 6 has a second inverter 10. The inverters 9, 10 are in particular power converters, inverters or rotary converters. The inverters 9, 10 are used to convert the battery voltage U Batt can be converted or inverted to AC voltages for supplying or operating three-phase machines 5, 6 respectively.

[0028] In particular, the two inverters 9, 10 are connected or coupled to the electrical energy storage 2. For example, for this purpose, both inverters 9, 10 can be connected via their inputs to the electrical energy storage 2. Thus, both inverters 9, 10 can be simultaneously supplied with, in particular, the same battery voltage U Batt can be supplied.

[0029] In particular, the inverters 9 and 10 can be referred to as drive inverters. In particular, the inverters 9 and 10 can be S3L inverters or three-level inverters.

[0030] To be able to charge the electric energy store 2, the electric energy store is electrically coupled to a vehicle-side charging terminal 3. The vehicle-side charging terminal 3 is, in particular, a charging socket or a charging outlet of the vehicle. In particular, a vehicle-external charging unit 11 can be connected to the vehicle-side charging terminal. The vehicle-external charging unit 11 can be, for example, a charging station or a charging column. In particular, the charging unit 11 is a DC charging source for providing a DC voltage. In particular, the charging unit 11 provides a charging voltage UL to the vehicle-side charging terminal 3.

[0031] To enable efficient charging of the electrical energy storage 2, the charging voltage UL must be greater than the battery voltage U Batt In other words, the battery voltage U Battand the charging voltage UL is 800 volts. Since this is not always the case, if the charging unit 11 can only provide a charging voltage L of less than 500 volts, the two inverters 9, 10, in particular the three-phase electric machines 5, 6, can be repurposed. Therefore, in this case, backward compatibility of the electric drive system 1 is required. To be able to dispense with an additional charging unit, such as a voltage converter or an on-board charger, the three-phase electric machines 5, 6, in particular the inverters 9, 10, for this charging operation are repurposed. In that case, either the first inverter 9 or the second inverter 10 operates as a boost or step-up converter for the charging operation of the vehicle, in particular the electric energy storage 2.

[0032] The electrical energy store 2 can be, for example, a vehicle battery, or a battery system or a number of partial batteries, or a high-voltage battery.

[0033] In that case, the electric drive system 1 can have a switching device 12 or a switching apparatus or a switching matrix in order to be able to use the inverters 9, 10 for the charging operation of the electric energy store 2. By means of this switching device 12, it is possible to set or switch to a charging process of the electric energy store 2 directly by the charging unit 11 or indirectly via the inverters 9, 10.

[0034] 1 shows the case of 800 volt DC charging, where the switching device 12 is switched to the first switching position, in which case the vehicle-side charging terminal 3 or the charging unit 11 is directly connected or coupled to the electric energy storage device 2, so that the electric energy storage device 2 can be charged with the charging voltage UL.

[0035] This 800 V DC direct charging is shown in Figure 1 by the current flow direction arrow 13. Next, in the following Figure 2, the 400 V DC charging process of the electrical energy storage device 2 is shown by way of example, in which the description of the electric drive system is the same as that of Figure 1.

[0036] In this case, the switching device 12 is switched to a second switching position different from the first switching position. In the second switching position, the vehicle-side charging terminal 3 is thus electrically connected or coupled to the first and second three-phase electric machines 5, 6 and the inverters 9, 10. The first and / or second inverters 9, 10 can convert or step-up the charging voltage UL, which in this case may be 400 volts, to the supply voltage UV. The charging voltage UL can thus be step-up transformed so that a voltage of 800 volts is present as the supply voltage UV. The electric energy storage device 2 can then be charged with this supply voltage. For this purpose, for example, in FIG. 2 , the current flow from the charging unit 11 through the three-phase machines 5, 6 and the inverters 9, 10 to the electric energy storage device 2 is indicated by the current flow arrow 14. In particular, in this case, at least one of the two inverters 9, 10 operates as a step-up converter. The other inverter 9, 10 operates in a clocked manner or as a clock generator. In this case, the current flow in the clock generating element is shown by the current flow direction arrow 15. In this case, the current flow direction arrow 15 of the clock operation is shown by a dashed line.

[0037] For example, various semiconductor switches of the inverters 9, 10 may be controlled for the step-up operation and clock generation operation of the first and / or second inverters 9, 10. For example, the inverters 9, 10 may have IGBTs or MOSFETs for this purpose. [Explanation of symbols]

[0038] 1 Electric drive system 2. Electrical Energy Storage 3 Vehicle charging terminal 4 drive shaft 5, 6 First and second three-phase electric machines 7, 8 First and second wheels 9, 10 First and second inverters 11 External charging unit 12 Switching Device 13, 14, 15 Current flow direction arrows U Batt Battery voltage UL Charging Voltage UV supply voltage

Claims

1. An electric drive system (1) for a vehicle, comprising: a first three-phase electric machine (5) and a second three-phase electric machine (6) for driving at least one drive shaft (4) of the vehicle; an electric energy storage (2) for supplying electricity to the first and second three-phase electric machines (5, 6) during driving operation of the vehicle, wherein a first inverter (9) of the first three-phase electric machine (5) and a second inverter (10) of the second three-phase electric machine (6) are respectively coupled to the electric energy storage (2); - a vehicle-side charging terminal (3) for electrically connecting the electrical energy store (2) to a charging unit (11) external to the vehicle; Equipped with the first and / or second inverter (9, 10) is capable of converting a charging voltage (UL) at the vehicle-side charging terminal (3) into a supply voltage (UV) for charging the electric energy store (2); the first three-phase electric machine (5) and the second three-phase electric machine (6) are arranged on the rear axle of the vehicle or on the front axle of the vehicle, the first three-phase electric machine (5) being able to drive a first wheel (7) of the front axle or the rear axle, and the second three-phase electric machine (6) being able to drive a second wheel (8) different from the first wheel (7) of the front axle or the rear axle, In the electric drive system (1), the first inverter (9) or the second inverter (10) can operate as a step-up transformer for charging the vehicle, The electric drive system (1) includes a switching device (12) for electrically coupling the vehicle-side charging terminal (3) to the first and second three-phase electric machines (5, 6) for charging the vehicle, wherein in a first switching position of the switching device (12), the vehicle-side charging terminal (3) is electrically connected directly to the electric energy storage device (2), and in a second switching position of the switching device (12), the vehicle-side charging terminal (3) is electrically connected to the first and second three-phase electric machines (5, 6); In the first switching position of the switching device (12), the electrical energy store (2) can be directly charged with the charging voltage (UL), and in the second switching position of the switching device (12), the electrical energy store (2) can be charged with the supply voltage (UV), which is higher than the charging voltage (UL). The electric drive system (1) is characterized in that

2. A method of operating an electric drive system (1) of a vehicle, comprising: - during driving of the vehicle, at least one drive shaft (4) of the vehicle is driven by a first three-phase electric machine (5) and a second three-phase electric machine (6); a first inverter (9) of the first three-phase electric machine (5) and a second inverter (10) of the second three-phase electric machine (6) are each supplied with electricity by an electric energy store (2); - for charging operation of the vehicle, a vehicle-side charging terminal (3) of the vehicle is electrically coupled to the first and second three-phase electric machines (5, 6); - the first and second inverters (9, 10) convert the charging voltage (UL) of the vehicle-side charging terminal (3) into a supply voltage (UV) for charging the electric energy store (2); the first three-phase electric machine (5) and the second three-phase electric machine (6) are arranged on the rear axle of the vehicle or on the front axle of the vehicle in such a way that the first three-phase electric machine (5) can drive a first wheel (7) of the front axle or the rear axle, and the second three-phase electric machine (6) can drive a second wheel (8) different from the first wheel (7) of the front axle or the rear axle, For charging the vehicle, the first inverter (9) or the second inverter (10) is operated as a step-up transformer, The electric drive system (1) includes a switching device (12) for electrically coupling the vehicle-side charging terminal (3) to the first and second three-phase electric machines (5, 6) for charging the vehicle, wherein in a first switching position of the switching device (12), the vehicle-side charging terminal (3) is electrically connected directly to the electric energy storage device (2), and in a second switching position of the switching device (12), the vehicle-side charging terminal (3) is electrically connected to the first and second three-phase electric machines (5, 6); In the first switching position of the switching device (12), the electrical energy store (2) can be directly charged with the charging voltage (UL), and in the second switching position of the switching device (12), the electrical energy store (2) can be charged with the supply voltage (UV), which is higher than the charging voltage (UL). The method, characterized in that

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