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

Abstract

The present invention relates to an electric drive system (1) for a vehicle, - a three-phase electric machine (2) for driving a vehicle; - an electric energy store (3) for supplying the three-phase electric machine (2) during the running operation of the vehicle; - an inverter (4) for the three-phase electric machine (2) electrically coupled to an electric energy storage (3) and a charging connection (5) on the vehicle side for electrically coupling the electric energy storage (3) to a charging unit (6) external to the vehicle, L ) into a supply voltage for charging an electrical energy store (3). The invention further relates to a method.

Description

[Technical Field]

[0001] The present invention relates to an electric drive system for a vehicle, which has a three-phase electric machine for driving the vehicle. Likewise, the electric drive system has an electric energy accumulator for supplying the three-phase electric machine during driving operation of the vehicle. Furthermore, the electric drive system has an inverter of the three-phase electric machine electrically coupled to the electric energy accumulator. The electric drive system has a vehicle-side charging connection for electrically coupling the electric energy accumulator to a charging unit external to the vehicle.

[0002] The invention further relates to a method for operating an electric drive system of a vehicle, wherein a three-phase electric machine is supplied with electricity by an electric energy accumulator during driving operation of the vehicle, whereby the vehicle is driven by the three-phase electric machine. [Background technology]

[0003] Electrically powered, especially battery-powered, vehicles such as battery electric vehicles (BEVs) often operate with battery voltages in the range of 800 volts. In that case, 800 volt charging columns are not always available, so such electric vehicles must also be charged with 400 volt charging columns.

[0004] For this purpose, for example, a boost converter can be used, in which case additional power electronics are installed in the electric vehicle, which adapts the voltage of the charging column to the vehicle's battery voltage.

[0005] For example, the prior art utilizes a two-system battery that can be switched between parallel and series, allowing the electric vehicle to be charged at either 400 volts or 800 volts.

[0006] Furthermore, from EP 0 699 599 B1 a switching mechanism for hybrid and electric vehicles is known, in which an additional voltage converter can be installed in the vehicle, which converts a 400 V DC voltage to an 800 V DC voltage. A similar device is known from EP 0 699 599 B1. The disadvantage of using such prior art additional voltage converters is that they require additional design space in the vehicle, which increases the vehicle weight, and the increased weight and, in particular, the increased design space leads to higher energy consumption and also higher costs. The use of switching batteries also has the disadvantage that additional bus bars and switches in the battery result in additional weight, design space, and increased costs. In particular, when such voltage converters and / or switching batteries are used, vehicle components that remain active during charging must be designed for a higher voltage range. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] DE102018009848A1 [Patent Document 2] DE102018009840A1 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is therefore to charge an electric vehicle with a voltage level of 800 volts more easily and without additional costs with a 400 volt charging column. [Means for solving the problem]

[0009] This problem is solved by an electric drive system and method according to the independent claims. Useful developments become apparent from the dependent claims.

[0010] One aspect of the present invention relates to an electric drive system for a vehicle, comprising: a three-phase electric machine for driving a vehicle; an electrical energy accumulator for supplying a three-phase electric machine with electricity during driving operation of the vehicle; an inverter for a three-phase electric machine, electrically coupled to an electric energy storage; a vehicle-side charging connection for electrically connecting the electric energy storage device to a charging unit external to the vehicle, -The inverter can convert the charging voltage of the vehicle-side charging connection into a supply voltage for charging the electrical energy store.

[0011] The proposed electric drive system allows electric vehicles, especially electric vehicles, with a voltage level of 800 volts to be charged more easily with 400 volt charging columns and / or charging units, since this backward compatibility can be achieved without additional costs. The electric vehicles can therefore be operated more efficiently, since simpler and improved means are provided for enabling the charging process to be carried out even with lower-voltage charging columns.

[0012] This advantage can be realized by having the inverter of the vehicle's three-phase electric machine, which is already present in the vehicle, additionally have a secondary function in addition to its primary function. The inverter's primary function is to provide AC voltage for the three-phase machine. The secondary function is the re-purpose of the inverter, particularly for charging operation of the vehicle at a 400-volt charging column. Thus, backward compatibility of the vehicle can be achieved without using additional components and / or parts, since the inverter is already present in the vehicle. The re-purpose of the inverter, particularly the utilization of the inverter's secondary function, can reduce the cost, weight, and design space of the electric vehicle.

[0013] Another aspect of the present invention relates to a method of operating an electric drive system of a vehicle, comprising: - the three-phase electric machine is supplied with electricity by the electric energy accumulator during the running operation of the vehicle, so that the vehicle is driven by the three-phase electric machine; -For vehicle charging operation, a charging connection on the vehicle side is coupled to an inverter of a three-phase electric machine; -The inverter converts the charging voltage of the charging connection on the vehicle side into a supply voltage for charging the electrical energy store.

[0014] This method makes the charging process for 800-volt electric vehicles easier and possible at no additional cost on a 400-volt charging column.

[0015] In particular, the method described immediately above may be implemented or performed using an electric drive system according to the previously described aspect or preferred embodiment thereof.

[0016] The features, advantages and advantageous embodiments of the electric drive system according to the invention should also be regarded as features, advantages and advantageous embodiments of the method according to the invention, and vice versa. In particular, the method according to the invention can be carried out by the relevant components of the electric drive system, alone or in operative connection therewith.

[0017] Each embodiment of one aspect should be considered a preferred embodiment of another 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] 1 shows a schematic block diagram of an electric drive system according to the present invention for a vehicle, illustrating 800 volt charging operation of the vehicle. [Figure 2] 2 shows another schematic block diagram of the electric drive system shown in FIG. 1, illustrating 400 volt charging operation of the vehicle. [Figure 3] 2 illustrates an alternative embodiment of the electric drive system shown in FIG. [Figure 4] 3 illustrates an alternative embodiment of the electric drive system shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

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

[0021] 1 shows, by way of example, a schematic block diagram of an electric drive system 1 for a vehicle. This may in particular be an electric drive vehicle, in particular a hybrid or electric vehicle. In particular, the electric drive system 1 serves to drive the vehicle for transport purposes. The electric drive system 1 may therefore be associated with a number of components or systems by means of which the vehicle can be driven.

[0022] For example, the electric drive system 1 may also be referred to as a drive unit, a switching mechanism, or an electric system.

[0023] For driving the vehicle, the electric drive system 1 may have a three-phase electric machine 2. In particular, the three-phase electric machine 2 is an electric machine, in particular an electric motor. The three-phase electric machine 2 in particular has exactly three phases A, B, and C. In particular, the three-phase electric machine 2 can be operated, for example, in motoring operation and thus as an electric motor. To operate the three-phase electric machine 2 in motoring operation, the three-phase electric machine 2 can be supplied with an electric AC voltage, in particular an electric high-voltage AC voltage, via phases A, B, and C, in particular via the phase lines or phase connections associated with phases A, B, and C. Phases A, B, and C of the three-phase electric machine 2 can in particular be wired via the neutral point.

[0024] To be able to supply the three-phase electric machine 2 with an AC voltage, the electric drive system 1 may have an electric energy accumulator 3. The electric energy accumulator 3 may be used on the one hand to supply the three-phase electric machine 2, vehicle components and / or vehicle systems with electric energy.

[0025] For example, the electrical energy accumulator 3 may be a plurality of batteries or a battery system. In particular, the electrical energy accumulator 3 is a battery, in particular a vehicle battery. For example, the electrical energy accumulator 3 is a high-voltage battery.

[0026] By means of the electrical energy accumulator 3, in particular the battery voltage U Batt In particular, the vehicle is a battery-powered vehicle with a voltage level of 800 volts. Batt This allows a voltage value of substantially 800 volts BC to be provided.

[0027] To be able to operate the three-phase electric machine 2, an AC voltage is required. This AC voltage is generated by the inverter 4 of the three-phase electric machine 2, which converts it into a voltage from the battery voltage U BattThe inverter 4 may be, for example, a converter or a power inverter. In particular, the inverter 4 may be called a drive inverter. In particular, the provision of an AC voltage for the three-phase electric machine 2 complies with the primary or main function of the inverter 4.

[0028] For example, the inverter 4 may be wired between the electrical energy store 3 and the three-phase electrical machine 2 .

[0029] In order to be able to charge, in particular, the electric energy accumulator 3, the electric drive system 1 can have a charging connection, in particular a vehicle-side charging connection 5. The vehicle-side charging connection 5 can be, for example, a charging socket of the vehicle. Via the vehicle-side charging connection 5, the vehicle, in particular the electric energy accumulator 3, can be electrically connected to a charging unit 6 external to the vehicle. The charging unit 6 can be, for example, a charging infrastructure, a charging system, a charging station, or a charging column.

[0030] The charging unit 6 can provide a voltage having a voltage value of, for example, 400 V or 800 V. In particular, any voltage value can be provided via the charging unit 6.

[0031] If the vehicle is an electric vehicle with an 800-volt drive, a charging means with a charging voltage of 800 volts is also specifically required. If the charging unit 6 provides a charging voltage of substantially 800 volts, the charging unit 6 can be directly connected to the electric energy accumulator 3, so that the electric energy accumulator 3 can be directly charged via the charging unit 6 with a voltage having a value of 800 volts. For example, the electric drive system 1 can have a switching device 7 for this purpose. In particular, the switching device 7 is arranged directly on the charging connection 5 on the vehicle side. The switching device 7 can be switched or converted between various switching positions or switching states.

[0032] In the case where a voltage value of 800 volts is provided by the charging unit 6 described immediately above, the switching device 7 can be in a first switching position. In the first switching position of the switching device 7, the vehicle-side charging connection 5, in particular the charging unit 6, is directly connected to the electric energy store 3, so that the voltage of the charging unit 6 can be used to charge the electric energy store 3 without having to be converted. For this purpose, the switching device 7 can have, for example, a switching element, so that current flows directly from the charging unit 6 to the electric energy store 3. For example, the switching device 7 can have a charging contactor, in particular a DC charging contactor, for this purpose.

[0033] In FIG. 1, the direction of current flow when the electrical energy store 3 is directly charged by the charging unit 6 with a current value of, for example, approximately 800 volts is visually indicated by the current flow arrow SF.

[0034] For example, the switching device 7 may have at least one electromagnetic compatibility filter 8 or a plurality of filter units. The electromagnetic compatibility filter 8 can in particular protect the charging unit 6 external to the vehicle from interference, for example electromagnetic interference.

[0035] Problems arise when using the charging unit 6 to provide voltages with current values ​​of 400 volts, especially voltage values ​​lower than 800 volts, because an additional voltage converter is required to boost such voltages, which are lower than the battery voltage, as in the prior art.

[0036] To address this, the inverter 4 may additionally have a secondary function in addition to its primary function. In other words, the inverter 4 of the three-phase electric machine 2 is used for the charging operation of the electric energy store 3. The inverter 4 therefore has additional functionality. In this case, the inverter 4 can be controlled so that it can be used for the charging operation of the electric energy store 3. In this case, the inverter 4 can be controlled or operated so that it functions as a step-up transformer or step-up chopper. The inverter 4 can therefore be used to increase the charging voltage U L can be converted or boosted to a higher supply voltage for charging the electrical energy store 3. Thus, by means of the inverter 4, the charging voltage U, which in this case is 400 volts, L into a supply voltage having a voltage value of substantially 800 volts. In this way, even if the charging voltage L provided by the charging unit 6 is too low, it can be converted into a higher supply voltage for charging the electric energy store 3 without any additional voltage conversion components. In particular, in the case of a 400-volt charging of a vehicle, the inverter 4 can be used as a step-up converter in order to adapt this 400-volt voltage of the charging unit 6 to the 800-volt voltage of the electric energy store 3.

[0037] To achieve this backward compatibility, the inverter 4 may be configured in a T-configuration as a three-level inverter, an S3 inverter, or a three-step inverter. In particular, the inverter 4 may be configured as a three-level inverter in NPC (Nutrial Point Claimed) technology or as a three-level inverter in an NPC circuit. In particular, the inverter 4 is a neutral-point clamped three-level inverter, which has a significantly higher voltage strength than the conventionally used two-level inverter.

[0038] The inverter 4 may have a flexible switching mechanism for each of the phases A, B, and C. Here, the inverter 4 may have individual semiconductor switches, such as IGBTs or MOSFETs: SA1, SA2, SA3, SA4, SB1, SB2, SB3, SB4, SC1, SC2, SC3, and SC4. The inverter 4 may also have a number of diodes: DA1, DA2, DA3, DA4, DZA1, DZA2, DB1, DB2, DB3, DB4, DZB1, DZB2, DC1, DC2, DC3, DC4, DZC1, and DZC2. The inverter 4 further has an intermediate circuit 9, which may have, for example, capacitors C1 and C2, which can be connected to the charging connection 5 on the vehicle side via a center tap Z.

[0039] By voltages, especially high voltages, is generally meant voltages greater than 50 V, especially greater than 60 V. Preferably, voltages, especially high voltages, are several hundred volts.

[0040] By the term "substantially" is meant a tolerance, especially of plus / minus 5 percent, especially 10 percent.

[0041] In the following FIG. 2, when the electric drive system 1 is in the charging process in the charging unit 6, a charging voltage U having a voltage value of 400 volts is L In this case, the switching device 7 is switched or changed over to a second switching position different from the first switching position. This changeover can be carried out automatically, in particular by a control unit. Here, FIG. 2 shows the current SF L This is the case for a charging voltage of, for example, 400 volts, U L4. The inverter 4 then boosts the 400 volts of the charging unit 6, in particular to 800 volts. To be able to do this, the individual semiconductor devices of the inverter 4 can be operated in a clocked manner, for example, by alternating between supplying current and clocking the devices. In this case, the current flow arrow SF G The clock operation of each device is shown by . As an example, in this embodiment, the semiconductor device SA2 is energized SF L For example, devices SB3 and SB4 are present as clock generators. By separating clocked and non-clocked devices, the semiconductors and / or diodes of inverter 4 can be loaded differently. In this way, reduced loading of inverter 4 is achieved.

[0042] In particular, the individuality of the three-phase electric machine 2 is utilized for voltage step-up, so that no additional devices and / or large, heavy chokes are required.

[0043] 3 and 4 show, on the one hand, slightly different wiring possibilities between the charging connection 5 on the vehicle side and the electric energy store 3. In FIG.

[0044] In particular, Figure 3 shows the same case of 800 volt charging as Figure 1. In this regard, the explanation for Figure 1 can be applied to Figure 3 as well.

[0045] Figure 4 shows a wiring change similar to that of Figure 3. In particular, the explanations given for Figures 2 and 1 can be applied to Figure 4.

[0046] In FIG. 4, the inverter 4 and in particular the devices of the electric drive system 2 are interchanged in energization and clocking. In particular, this allows for many variations in interchange regarding the energization of the devices and the clocking of the devices. Thus, here too, the energization SF LThe current carrying device is denoted by SF G A clock generating device is indicated by [Explanation of symbols]

[0047] 1 Electric drive system 2. Three-phase electric machines 3 Electrical energy storage 4 inverters 5 Charging connection on the vehicle side 6. External charging unit 7 Switching device 8 Electromagnetic Compatibility Filters 9 Intermediate circuit A, B, C phases of a three-phase machine DA1, DA2, DA3, DA4, DZA1, DZA2, DB1, DB2, DB3, DB4, DZB1, DZB2, DC1, DC2, DC3, DC4, DZC1, DZC2 Diode SA1, SA2, SA3, SA4, SB1, SB2, SB3, SB4, SC1, SC2, SC3, SC4 semiconductor devices SF energized arrow science fiction L Charging operation current arrow science fiction G Clock movement energizing arrow C1 and C2 capacitors Z center tap U L Charging voltage U Batt Battery voltage

Claims

1. An electric drive system (1) for a vehicle, comprising: a three-phase electric machine (2) for driving the vehicle; an electric energy accumulator (3) for supplying the three-phase electric machine (2) with electricity during running operation of the vehicle; an inverter (4) of the three-phase electric machine (2), electrically coupled to the electric energy storage (3); a vehicle-side charging connection (5) for electrically connecting the electric energy storage (3) to a charging unit (6) external to the vehicle, The inverter (4) controls the charging voltage (U Ｌ ) can be converted into a supply voltage for charging said electrical energy store (3), the inverter (4) of the three-phase electric machine (2) is configured as a three-level inverter; The electric drive system (1) comprises a switching device (7) for electrically coupling the vehicle-side charging connection (5) to the inverter (4) of the three-phase electric machine (2) for charging operation of the vehicle, the switching device (7) comprising an electromagnetic compatibility filter (8) for protecting the charging unit (6) external to the vehicle from interference, and the vehicle-side charging connection (5) can be directly connected to a center tap (Z) of the inverter (4) by the switching device (7) via the electromagnetic compatibility filter (8).

2. 2. The electric drive system (1) according to claim 1, characterized in that the inverter (4) is operable as a step-up transformer for vehicle charging operation.

3. 3. The electric drive system (1) according to claim 1, wherein the vehicle-side charging connection (5) is directly connected to the electric energy storage device (3) when the switching device (7) is in a first switching position, and the vehicle-side charging connection (5) is connected to the inverter (4) when the switching device (7) is in a second switching position.

4. A method of operating an electric drive system (1) of a vehicle, comprising: The electric drive system (1) comprises a three-phase electric machine (2) for driving the vehicle and an electric energy storage (3) for supplying electricity to the three-phase electric machine (2) during a running operation of the vehicle, and the three-phase electric machine (2) is supplied with electricity by the electric energy storage (3) during a running operation of the vehicle, thereby driving the vehicle by the three-phase electric machine (2), A charging connection (5) on the vehicle side of the vehicle is coupled to an inverter (4) of the three-phase electric machine (2) for charging operation of the vehicle; The inverter (4) controls the charging voltage (U Ｌ ) into a supply voltage for charging the electrical energy store (3), the inverter (4) of the three-phase electric machine (2) is configured as a three-level inverter; The electric drive system (1) comprises a switching device (7) for electrically coupling the vehicle-side charging connection (5) with the inverter (4) of the three-phase electric machine (2) for charging operation of the vehicle; The method is characterized in that the switching device (7) has an electromagnetic compatibility filter (8) for protecting a charging unit (6) outside the vehicle from interference, and the charging connection (5) on the vehicle side can be directly connected to the center tap (Z) of the inverter (4) by the switching device (7) via the electromagnetic compatibility filter (8).

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