Voltage converter arrangement, electrical drive system and method for operating a voltage converter arrangement

Abstract

Voltage converter arrangement for an electric drive system. The voltage converter arrangement comprises at least two power converters. One power converter is designed to convert electrical energy from a charging port for charging an electrical energy storage device and, alternatively, to drive an electric machine using electrical energy from the electrical energy storage device in partial load operation. Furthermore, the electric machine can be driven in a higher power range using a second power converter.

Description

Technical field

[0001] The present invention relates to a voltage converter arrangement and a method for operating a voltage converter arrangement. The present invention further relates to an electric drive system with such a voltage converter arrangement. In particular, such a voltage converter arrangement can be used in an electrically powered vehicle. background

[0002] Vehicles that are fully or partially electrically powered include an electric drive system. In such an electric drive system, electrical energy in the form of direct current (DC) can be supplied by an electrical energy storage device, for example, a traction battery. This electrical voltage can be converted by an electrical converter into another voltage, preferably a single-phase or multi-phase alternating current (AC) voltage, to drive an electric motor. When the vehicle is stationary, the electrical energy storage device can be recharged by means of electrical energy from an external energy source. For this purpose, a charging circuit can be provided which converts the charging voltage supplied by the external energy source into an electrical voltage suitable for recharging the electrical energy storage device.

[0003] For example, the publication DE 10 2014 219 909 A1 describes a charging circuit for an electrical energy storage device and an electric drive system for an electric vehicle. Disclosure of the invention

[0004] The present invention provides a voltage converter arrangement, an electrical drive system, and a method for operating a voltage converter arrangement with the features of the independent claims. Further advantageous embodiments are the subject of the dependent claims. Accordingly, the following is planned:

[0005] A voltage converter arrangement comprising a first electrical connection, a second electrical connection, and a third electrical connection. The voltage converter arrangement further comprises a first power converter, a second power converter, and a switching device. The first electrical connection is designed to be connected to an electrical energy storage device. The second electrical connection is designed to be connected to an electrical machine. The third electrical connection is designed to be connected to an AC voltage source. The AC voltage source can, in particular, be an external power source that provides energy for charging an energy storage device connected to the first electrical connection. The first electrical power converter comprises a DC voltage connection and an AC voltage connection.The DC output of the first converter is electrically coupled to the first electrical output of the voltage converter assembly. The AC output of the first converter is electrically coupled to the second electrical output of the voltage converter assembly. The second converter also comprises a DC output and an AC output. The DC output of the second converter is electrically coupled to the first electrical output. The switching device is arranged between the AC output of the second converter and the second electrical output. The switching device is specifically designed to selectively connect or disconnect the electrical connection between the AC output of the second converter and the second electrical output.The third electrical connection is electrically coupled to the AC connection of the second converter. Furthermore, the following is planned:

[0006] An electric drive system comprising a voltage converter arrangement according to the invention and an electric machine. The electric machine is electrically coupled to the second electrical connection. The third electrical connection can be electrically coupled to a charging port of an electric vehicle. Finally, the following is planned:

[0007] A method for operating a voltage converter arrangement, in particular a voltage converter arrangement according to the invention. In a first operating mode, the first converter is deactivated and the second converter transfers electrical energy from the first electrical terminal to the second electrical terminal. In a second operating mode, the first converter transfers electrical energy from the first electrical terminal to the second electrical terminal. The second converter can optionally be active and also transfer electrical energy from the first electrical terminal to the second electrical terminal, or alternatively be deactivated. In a third operating mode, the first converter is deactivated and the second converter transfers electrical energy from the third electrical terminal to the first electrical terminal. Advantages of the invention

[0008] The present invention is based on the understanding that in electric drive systems, such as those used for electric vehicles, the electrical energy is supplied by a rechargeable energy storage device. Firstly, a circuit arrangement is required to drive the electric machine of such a drive system. This circuit converts the electrical energy from the energy storage device into a voltage suitable for driving the electric machine with the desired parameters. Furthermore, conventional systems include an additional charging circuit that converts the voltage from an external energy source into a voltage suitable for charging the energy storage device.

[0009] Furthermore, the present invention is based on the understanding that, firstly, the electric machine of such a drive system for an electric vehicle is predominantly operated with an electrical power output that is significantly lower than the maximum peak load that the electric machine can provide. Likewise, the electrical power with which the electrical energy storage device in an electric vehicle is charged during a charging process on a single- or multi-phase AC power grid is generally significantly lower than the maximum power output of the electric machine in such a drive system.

[0010] Based on these findings, the present invention aims to create a concept that enables both the efficient provision of electrical energy for driving the electric machine of such a drive system and the efficient charging of the electrical energy storage device. In particular, the concept according to the invention allows the necessary components for both charging the electrical energy storage device and driving the electric machine to be combined in such a compact manner that all relevant components can preferably be arranged in a common housing, preferably as a single assembly.

[0011] According to one embodiment, the voltage converter arrangement is designed to transfer electrical energy from the first terminal to the second electrical terminal in a first operating mode. In this first operating mode, the electrical energy is transferred exclusively by the second converter from the first electrical terminal to the second electrical terminal, while the first converter is deactivated. Furthermore, the voltage converter arrangement can be designed to transfer electrical energy from the first electrical terminal to the second electrical terminal in a second operating mode using the first converter.In this second operating mode, it is possible either to deactivate the second electrical converter or to transfer electrical energy from the first electrical terminal to the second electrical terminal by operating the first and second converters in parallel. Furthermore, the voltage converter arrangement can be designed to deactivate the first converter in a third operating mode and transfer electrical energy from the third electrical terminal to the first electrical terminal using the second converter. In this way, electrical energy can be transferred from an external power source connected to the third electrical terminal to an electrical energy storage device connected to the first electrical terminal in order to charge the energy storage device.The second power converter can be designed for a maximum output that, on the one hand, meets the requirements for maximum charging power, i.e., the energy transfer from the third electrical connection to the first electrical connection, and, on the other hand, additionally or alternatively, also meets the requirements for expected partial load operation, i.e., operation with reduced power from the electric machine at the second electrical connection. The increased power demand of the electric machine during peak load can then be met in the second operating mode by activating the first power converter.

[0012] According to one embodiment, the voltage converter arrangement includes a further switching device. This further switching device can be arranged between the AC voltage terminal of the first converter and the second electrical terminal. The further switching device can be designed to interrupt the electrical connection between the AC voltage terminal of the first converter and the second electrical terminal in the third operating mode. In this way, it can be ensured that no electrical voltage is present at the AC voltage terminal of the first converter during charging in the third operating mode.

[0013] According to one embodiment, the voltage converter arrangement includes a control unit. The control unit can be designed to control both the first and the second power converter. Furthermore, the control unit can also be designed to control the switching device and, if applicable, the additional switching device. In this way, all control signals for the voltage converter arrangement can be generated and provided by a single control unit. This enables a streamlined and compact design.

[0014] According to one embodiment, the voltage converter assembly comprises a housing. The housing can contain the first power converter, the second power converter, and the switching device. Furthermore, the first electrical connection, the second electrical connection, and the third electrical connection can be arranged on the housing. In this way, a compact assembly can be provided which can efficiently drive an electric machine connected to the second electrical connection and is also suitable for efficiently charging an energy storage device connected to the first electrical connection.

[0015] According to one embodiment, the voltage converter arrangement includes a DC-DC converter. The DC-DC converter can be arranged between the first electrical terminal and the DC terminal of the second converter. In particular, it can be a bidirectional DC-DC converter designed to convert a DC voltage supplied at the first electrical terminal into another DC voltage and supply it at the DC terminal of the second converter, and also to convert a DC voltage supplied by the second converter at its DC terminal into another DC voltage and supply it at the first electrical terminal. Optionally, a switching component can be provided in parallel with the DC-DC converter, designed to bypass the DC-DC converter.

[0016] According to one embodiment, the voltage converter arrangement includes a filter device. The filter device can, for example, include a capacitor for each connection point of the AC input of the second converter, arranged between the respective connection point of the AC input of the second converter and a node. The node can optionally be connected to a reference potential. Furthermore, inductors can be provided in the filter device between the connection points of the AC input of the second converter and the corresponding connection points of the second electrical input. The components of the filter device can, for example, be designed for triangular current mode modulation (TCM modulation).

[0017] According to one embodiment, the filter device can be designed to be deactivated. For this purpose, switching elements can be provided, for example, between the capacitors and the common node, which can be opened or closed. Thus, the filter device can be activated for the first operating mode, for example, to achieve optimized control of the electric machine. Furthermore, the filter device can be deactivated in the second operating mode and, if applicable, the third operating mode, to prevent any disruptive influence of the filter components in these operating modes.

[0018] The above embodiments and further developments can be combined with one another as appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention. Brief description of the drawings

[0019] Further features and advantages of the invention are explained below with reference to the figures. These show: Fig. 1: a schematic representation of a block diagram to illustrate a voltage converter arrangement in an electric drive system according to an embodiment; Fig. 2: a schematic representation of a block diagram to illustrate a voltage converter arrangement according to a further embodiment; and Fig. 3: a flowchart such as may underlie a method for operating a voltage converter arrangement according to one embodiment. Description of embodiments

[0020] Fig. Figure 1 shows a schematic representation of a voltage converter arrangement 1, such as that which can be used in an electric drive system, for example in an electric vehicle. The voltage converter arrangement 1 comprises a first electrical connection 11, a second electrical connection 12, and a third electrical connection 13. The first electrical connection 11 can be connected to a DC network, in particular a DC voltage source such as a battery 2, especially a traction battery of an electric vehicle. The second electrical connection 12 can be connected to an AC network, in particular an AC voltage load such as an electric machine 3. The third electrical connection 13 can be connected to an external AC voltage source. For this purpose, the third electrical connection 13 can, for example, be connected to the charging port 4 of an electric vehicle.This charging port 4 can be configured to be connected to an external energy source, in particular an external AC voltage source, such as the charging station for an electric vehicle.

[0021] The voltage converter arrangement 1 further comprises at least two power converters 20, 30. A first power converter 20 is arranged between the first electrical terminal 11 and the second electrical terminal 12. A DC terminal 21 of the first power converter 20 is connected to the first electrical terminal 11. An AC terminal 22 of the first power converter 20 is connected to the second electrical terminal 12 of the voltage converter arrangement 1. Optionally, as described below, a switching device can be provided between the AC terminal 22 of the first power converter 20 and the second electrical terminal 12. The first power converter 20 can, in particular, be an inverter designed to generate a single-phase or multi-phase AC voltage from a DC voltage supplied at the DC terminal 21 and to supply this AC voltage at the AC terminal 22.Optionally, the power converter 20 can also convert an alternating voltage applied to the AC voltage terminal 22 into a direct voltage and provide this at the DC voltage terminal 21. Since the basic principle of such power converters, for example based on several half-bridges or similar devices, is considered well-known, it will not be described in detail here.

[0022] The second power converter 30 is also arranged between the first electrical terminal 11 and the second electrical terminal 12. The DC terminal 31 of the second power converter 30 is also connected to the first electrical terminal 11. A switching device 40 is provided between the AC terminal 32 of the second power converter 30 and the second electrical terminal 12. This switching device 40 can selectively connect or disconnect the connections between the AC terminal 32 of the second power converter 30 and the second electrical terminal 12.

[0023] The third electrical connection 13 is connected to the AC voltage connection 32 of the second power converter 30. A filter and / or switching device 50 may optionally be provided between the third electrical connection 13 and the AC voltage connection 32 of the second power converter 30. This device may include the filter and protective elements required for charging operation, such as fuses or similar components. Furthermore, this filter and switching unit 50 may also switch the phases and disconnect the third electrical connection 13, and thus the charging connection 4 of an electric vehicle, from the AC voltage connection 32 of the second power converter 30.

[0024] A common control unit 90 can be provided for controlling the first electrical power converter 20 and the second power converter 30, as well as the switching device 40 and, if applicable, other components to be controlled. Thus, all components of the voltage converter arrangement 1 can be centrally controlled by a common control unit 90.

[0025] The first power converter 20, the second power converter 30, the switching device 40, and optionally other components such as the control unit 90, the filter and switching unit 50, as well as any other components described below, can be arranged in a common housing 10. All three electrical connections—that is, the first electrical connection 11, the second electrical connection 12, and the third electrical connection 13—can also be located on this housing 10. This allows for the creation of a compact assembly to which only the electrical energy storage device 2, the electric motor 3, and the charging port 4 need to be connected. Optionally, a further interface (not shown here) can be provided for communication with the control unit 90, for transmitting setpoints and outputting status messages.

[0026] The electric machine 3 of an electric drive system for an electric vehicle is typically operated predominantly at significantly below its maximum power output. Accordingly, for such partial load operation, the voltage converter arrangement 1 only needs to provide electrical power that is significantly below the maximum peak power of the electric drive system. For this purpose, in a first operating mode, the second converter 30 can, for example, be designed for a power range adapted to this partial load operation. This partial load operation can, for example, comprise a maximum of 10, 15, or 25 percent of the maximum peak load of the electric drive system. Furthermore, the maximum charging power for charging the energy storage device 2 connected to the first electrical terminal 11 can also be considered when dimensioning this second converter 30.Accordingly, the second electrical power converter 30 can, for example, be designed for a maximum power output of 3.6 kW, 11 kW, or 22 kW. Depending on the application, other suitable power ranges are of course also possible.

[0027] Based on the configuration described above, in a first operating mode for partial load operation of the electric drive system, the second converter 30 can convert a DC voltage supplied at the first electrical terminal 11 into an AC voltage and supply this to the electric machine 3 at the second electrical terminal 12. In this operating mode, the first converter 20 is deactivated. In particular, a switching state can be set in the first converter 20 so that the connection points at the AC terminal 22 of the first converter 20 are electrically isolated from each other.

[0028] If the power demand of the electric drive system exceeds the maximum capacity of the second converter 30, or if a predefined power demand threshold is exceeded, the first converter 20 can be activated in a second operating mode. This first converter 20 can be dimensioned to provide higher electrical power. In particular, the first converter 20 can be dimensioned such that it can provide the maximum required peak power for the electric machine 3, either alone or in parallel with the second converter 30. Accordingly, for power demands above the previously described partial load operation, either the first converter 20 can be operated alone while the second converter 30 is deactivated, or alternatively, the first converter 20 and the second converter 30 can be operated in parallel to drive the electric machine 3.

[0029] Furthermore, the described voltage converter arrangement 1 can also be used in a third operating mode to charge the electrical energy storage device 2 at the first electrical terminal 11. For this purpose, the electrical connection to the second electrical terminal 12 can be interrupted by opening the switching device 40 between the second converter 30 and the second electrical terminal 12. Electrical energy can then be supplied from the third electrical terminal 13 to the AC terminal 32 of the second converter 30. The second converter 30 can convert the AC voltage present at the AC terminal 32 into a DC voltage suitable for charging the electrical energy storage device 2 connected to the first electrical terminal 11.

[0030] Fig. Figure 2 shows a schematic representation of a voltage converter arrangement 1 according to a further embodiment. The voltage converter arrangement according to Fig. 2 differs from the previously described voltage converter arrangement in particular in that it shows additional, preferably optional, components. However, all previously stated aspects also apply to this voltage converter arrangement 1 in connection with Fig. 1. Statements made.

[0031] In the voltage converter arrangement according to Fig. For example, a further switching device 80 is provided between the AC voltage terminal 22 of the first power converter 20 and the second electrical terminal 12. This further switching device 80 can selectively disconnect or connect the electrical connection between the connection points on the AC voltage terminal 22 of the first power converter 20 and the corresponding connection points on the second electrical terminal 12. In particular, this further switching device 80 can be opened, for example, when the first electrical power converter 20 is not active, for example, in the first operating mode in which the electrical power for driving the electric machine 3 is provided exclusively by the second power converter 30.If the first power converter 20 is active, for example in the second operating mode for higher drive power of the electric machine 3, the further switching device 80 can be closed. Likewise, the further switching device 80 can be open in the third operating mode for charging the electrical energy storage device 2 at the first electrical terminal 11.

[0032] Furthermore, a filter device 70 can be provided at the AC voltage terminal 32 of the second power converter 30. This filter device 70 can comprise any suitable filter components that are suitable for reducing electromagnetic interference and / or for shaping the voltage or current of the AC voltage provided at the AC voltage terminal 32 of the second power converter 30, for example, to generate a voltage that is as sinusoidal as possible. For example, as in Fig. Figure 2 shows that the filter device 70 comprises inductors 71, which are provided at the respective connection points of the AC voltage terminal 32 of the second converter 30. Furthermore, the filter device 70 can comprise capacitors 72, wherein, for example, one capacitor 72 is provided between a node K and the AC voltage lines that connect the AC voltage terminal 32 of the second converter 30 to the second electrical terminal 12. A switching element 73 can also be provided between each capacitor 72 and node K. In this way, the capacitors 72 can be deactivated. For example, the capacitors 72 can be activated by closing the switching elements 73 when, in the first operating mode, the second electrical converter 30 provides the electrical energy to drive the electric machine 3 in partial load operation.In the other operating modes, that is, when the first electrical power converter 20 is active or when the electrical energy storage device 2 is being charged, the switching elements 73 can be opened to deactivate the capacitors.

[0033] Optionally, node K can also be connected to a reference potential, for example the negative connection point of the DC voltage connection 31 of the second converter 30.

[0034] Furthermore, a DC-DC converter 60 can optionally be provided between the first electrical terminal 11 and the DC-DC terminal 31 of the second power converter 30. In particular, the DC-DC converter 60 can be a bidirectional DC-DC converter, that is, a DC-DC converter that can convert an electrical DC voltage from the first electrical terminal 11 into another DC voltage and provide this at the DC-DC terminal 31 of the second power converter 30. Conversely, the DC-DC converter 60 can also convert a DC voltage from the DC-DC terminal 31 of the second power converter 30 into another DC voltage and provide this at the first electrical terminal 11. Optionally, a switching component 61 can be provided in parallel with the DC-DC converter 60.By closing this switching component 61, the DC voltage converter 60 can be bypassed when the DC voltage converter 60 is not active.

[0035] Fig. Figure 3 shows a flowchart illustrating the procedure for operating a voltage transformer arrangement, in particular one of the voltage transformer arrangements 1 described above. Accordingly, the procedure can, in principle, comprise any steps suitable for implementing or operating the voltage transformer arrangements 1 described above. Similarly, the voltage transformer arrangements 1 described above can also comprise any components suitable for implementing the procedure described below.

[0036] The method comprises a first operating mode S1 in which the first power converter 20 is deactivated. In this first operating mode, electrical energy is transferred from the first electrical terminal 11 to the second electrical terminal 12 by means of the second power converter 30.

[0037] In a second operating mode S2, electrical energy is transferred from the first electrical terminal 11 to the second electrical terminal 12 via the first power converter 20. In this second operating mode, the second power converter 30 can be deactivated. Alternatively, electrical energy can also be transferred from the first electrical terminal 11 to the second electrical terminal 12 by operating the first power converter 20 and the second power converter 30 in parallel.

[0038] In a third operating mode S3, the first power converter 20 is deactivated and electrical energy is transferred from the third electrical terminal 13 to the first electrical terminal 11. In this third operating mode S3, an electrical energy storage device 2 connected to the first electrical terminal 11 can therefore be charged using electrical energy from the third electrical terminal 13.

[0039] In summary, the present invention relates to a voltage converter arrangement for an electric drive system. The voltage converter arrangement comprises at least two power converters. One power converter is designed to convert electrical energy from a charging port for charging an electrical energy storage device and, alternatively, to drive an electric machine using electrical energy from the electrical energy storage device in partial load operation. Furthermore, the electric machine can be driven in a higher power range using a second power converter. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2014 219 909 A1

[0003]

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