Voltage converter assembly, electric drive system, and method for operating a voltage converter assembly

Abstract

The invention relates to a voltage converter assembly in an electric drive system, said voltage converter assembly being capable of actuating a connected electric machine in one operating mode and converting an input DC voltage into an output DC voltage in another operating mode. In order to convert the input DC voltage into the output DC voltage, the phase windings of the connected electric machine can be used as inductors. In the process, the individual phase windings are energized individually on the basis of the rotor position and on the basis of a target value specification for the total current.

Description

[0001] Description

[0002] title

[0003] Voltage converter arrangement, electric drive system and method for

[0004] Operating a voltage transformer arrangement

[0005] Technical area

[0006] The present invention relates to a voltage converter assembly, an electric drive system, and methods for operating a voltage converter assembly. In particular, the present invention relates to voltage conversion using components of an electric drive system.

[0007] State of the art

[0008] Fully or at least partially electrically powered vehicles typically have an electric drive system in which electrical energy is supplied from an energy storage device, such as a traction battery, to an electric motor via a power converter. The electrical energy storage device used for this purpose can be charged using an external energy source. This usually requires a separate charging circuit.

[0009] Furthermore, it is also possible to use components of the electric drive system to charge the electrical energy storage device. Such an arrangement is described, for example, in the publication DE 10 2018 207 188 A1.

[0010] Disclosure of the invention

[0011] The present invention provides a voltage converter assembly, an electric drive system, and a method for operating a voltage converter assembly having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims.

[0012] Accordingly, it is provided:

[0013] A voltage converter arrangement with a voltage converter circuit and a control device. The voltage converter circuit is designed to be connected to a multi-phase electrical machine. Furthermore, the voltage converter circuit is designed to convert an input DC voltage provided at the voltage converter circuit into a predetermined output DC voltage when the electrical machine is at a standstill in a first operating mode. The control device is designed to adjust electrical currents through at least one phase winding of a multi-phase electrical machine connected to the voltage converter circuit during the conversion of the electrical input DC voltage into the predetermined output DC voltage. The adjustment of the electrical currents through the respective phase winding takes place in particular using a rotor position of the electrical machine.

[0014] Furthermore, it is planned:

[0015] An electric drive system with a voltage converter arrangement according to the invention and a multiphase electric machine. The electric machine is electrically coupled to the voltage converter arrangement.

[0016] Finally, it is planned:

[0017] A method for operating a voltage converter arrangement. The voltage converter arrangement comprises a voltage converter circuit. The voltage converter circuit is designed to be connected to a multi-phase electrical machine. The method comprises a step for determining a rotor position of an electrical machine connected to the voltage converter circuit. The method further comprises a step for controlling the voltage converter circuit to convert an input DC voltage provided to the voltage converter circuit into a predetermined output DC voltage. The conversion of the input DC voltage into the output DC voltage occurs in particular when the connected electrical machine is at a standstill.In this case, the method according to the invention individually adjusts electrical currents through at least one phase winding of the multiphase electrical machine connected to the voltage converter circuit during the conversion of the electrical input DC voltage to the predetermined output DC voltage. The electrical currents are adjusted, in particular, using the determined rotor position of the electrical machine.

[0018] Advantages of the invention

[0019] The present invention is based on the finding that the resulting inductances of the individual phase windings of a multi-phase electrical machine can vary depending on the rotor position of the electrical machine, particularly in the case of permanently excited synchronous machines. Therefore, if components of the electrical drive system are used to convert an input DC voltage into an output DC voltage, the electrical properties resulting from the position-dependent inductances can also fluctuate.

[0020] It is therefore an idea of ​​the present invention to take this finding into account and to consider the rotor position and the resulting variable inductances of the phase windings in an electrical machine when using components of an electrical drive system for voltage conversion.

[0021] For this purpose, when using components of an electrical drive system to convert an input DC voltage into an output DC voltage, the electrical currents through the phase windings, i.e., the stator windings of a connected electrical machine, are individually adjusted. In other words, if multiple phase windings in a connected electrical machine are used for voltage conversion, the electrical currents through the phase windings used can be adjusted separately. The respective currents through the individual phase windings can be adjusted, in particular, taking into account the current rotor position and the resulting individual inductances of the phase windings, as well as the required total current.

[0022] This makes it possible to adapt the entire system for converting the input DC voltage into the output DC voltage to the resulting inductances of the connected electrical machine. This allows the operating behavior of the voltage conversion to be optimized.

[0023] In particular, by taking the rotor position and the resulting inductances into account when energizing the phase windings, the resulting current and / or voltage ripple can be minimized. This also reduces the requirements for filtering or interference suppression measures.

[0024] In particular, for example, the required capacitance for compensating the aforementioned current and / or voltage regulators can be minimized. Furthermore, the inventive individual energization of the phase windings depending on the rotor position can also minimize the torque occurring in the electric machine during voltage conversion.

[0025] According to one embodiment, the voltage converter circuit comprises a DC voltage connection and an AC voltage connection. The DC voltage connection is designed to be connected to an electrical energy storage device, for example, a battery. The AC voltage connection is designed to be connected to the electric machine. Furthermore, the voltage converter circuit can be designed to receive the input DC voltage between a connection point of the DC voltage connection and a motor connection in the first operating mode and to provide the output DC voltage between the first connection point and a second connection point of the DC voltage connection.Thus, the voltage converter circuit can, for example, be an electrical power converter designed to control an electrical machine using the electrical energy provided by the electrical energy storage device at the DC voltage connection. Additionally or alternatively, such an electrical power converter can charge the electrical energy storage device using electrical energy provided in the form of an AC voltage by the electrical machine. Such a circuit arrangement can be used in a further operating mode, referred to here as the first operating mode, to convert the DC voltage provided by an external DC voltage source into a DC voltage suitable for charging the electrical energy storage device. For this purpose, the electrical energy storage device is connected unchanged to the DC voltage connection.The input DC voltage can be provided between a connection point (preferably the negative pole) of the electrical energy storage device and a motor connection. Depending on the configuration, either a phase connection of the electrical machine or a star point of the electrical machine can be used as the motor connection. In other words, the input DC voltage from the external energy source is provided between a phase connection or the star point of the electrical machine and a connection point of the electrical energy storage device.

[0026] DC voltage connection of the voltage converter circuit.

[0027] According to one embodiment, the control device of the voltage converter arrangement is designed to set the electrical current or currents through at least one of the phase windings using a setpoint for a total current to be set. The total current can refer, for example, to the electrical current at the input or output of the voltage converter arrangement. Accordingly, the total current to be set can be divided between one or more of the phase windings according to the rotor position. For example, with relatively low total currents it may be appropriate to assign the current entirely to one phase winding. For higher currents, however, it may be necessary to divide the total current between two or more phase windings. During this division, the rotor position or the inductances resulting from the rotor position for the individual phase windings can also be taken into account.

[0028] According to one embodiment, the control device of the voltage converter arrangement is designed to determine inductance values ​​for the phase windings of the multi-phase electrical machine connected to the voltage converter circuit. The determination of the individual inductances for the respective phase windings can be carried out, in particular, using the rotor position of the electrical machine. Furthermore, the control device is designed to adjust the electrical currents through the phase windings of the electrical machine using the determined inductance values. By determining the resulting inductance values ​​for the phase windings of the connected electrical machine, a variable is thus available that is very well suited to determining the electrical currents through the respective phase windings.

[0029] According to one embodiment, the voltage converter arrangement comprises a memory device. The memory device is designed to provide data for a relationship between the rotor position of the electrical machine and the electrical currents to be set in the phase windings of the electrical machine. In this case, the control device can be designed to read the data stored in the memory device and to set the electrical currents through the individual phase windings of a connected electrical machine using the data read from the memory device. For example, the relationships between the rotor position and the respective electrical currents to be set can be stored in the form of a so-called lookup table or in any other form.In addition to a tabular format, it is also possible to provide a formulaic relationship between the rotor position and the electrical currents to be set. Furthermore, more complex relationships are also possible, in which additional parameters are taken into account in addition to the rotor position and the electrical currents to be set. Such additional parameters can include, for example, input current, output current, input voltage, output voltage, or any other operating parameters, such as temperatures, especially rotor and / or stator temperatures, etc.

[0030] According to one embodiment, the control device is designed to adjust a phase shift between the electrical currents through at least two phase windings of the multi-phase electrical machine connected to the voltage converter circuit. The adjustment can be made using a rotor position of the electrical machine and, if applicable, the required charging current. In particular, a phase shift between electrical alternating voltages applied to the individual rotor phases can be adjusted depending on the rotor position and / or the resulting individual inductances of the individual phase windings. For example, even with pulse-width modulation for applying electrical currents to the individual phase windings, the rising or falling edges of the individual pulses or the pulse centers can be adjusted depending on the rotor position.

[0031] According to one embodiment, the control device of the voltage converter assembly is designed to receive a signal from a rotor angle sensor of the electric machine. In this case, the electrical currents through the phase windings of the electric machine can be adjusted using the received signal from the rotor angle sensor. In other words, the respective rotor position is determined by receiving a corresponding sensor signal from a rotor angle sensor coupled to the electric machine.

[0032] According to a further embodiment, the control device of the voltage converter arrangement is designed to calculate or estimate the rotor position of the multi-phase electrical machine connected to the voltage converter circuit. Accordingly, the electrical currents through the phase windings of the electrical machine can be adjusted using the rotor position thus determined. In this case, the rotor position of the connected electrical machine can be calculated or estimated based on a mathematical model or the like.

[0033] According to one embodiment, the control device of the voltage converter arrangement is designed to adjust the electrical currents through the phase windings of the electrical machine using additional operating parameters of the voltage converter arrangement and / or the multi-phase electrical machine connected to the voltage converter circuit. This allows an optimal operating point to be determined in each case, which, in addition to the rotor position of a connected electrical machine and the resulting individual inductances in the phase windings, also takes into account other operating parameters for optimal operation.Such further operating parameters may include, for example, the voltage / current level of the input and / or output voltage, operating temperatures, in particular calculated, estimated or measured temperatures in or on the connected electrical machine, in particular on the stator and / or rotor of the electrical machine, as well as any other suitable operating parameters.

[0034] According to one embodiment, the voltage converter arrangement is further configured to provide an electrical voltage for controlling the multi-phase electrical machine in a second operating mode. In other words, the voltage converter arrangement according to the invention is suitable, on the one hand, for controlling a connected electrical machine. Furthermore, the voltage converter arrangement is also suitable for utilizing the inductances of the phase windings of this connected electrical machine for voltage conversion of an input DC voltage into an output DC voltage. Thus, for example, an electrical drive system can be realized which draws electrical energy from a connected energy storage device for operating the electrical machine.This electrical energy storage device can be charged using components of the electrical machine's control circuit as well as the inductances of the phase windings of the connected electrical machine. This enables multiple use of the existing components.

[0035] The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0036] Short description of the drawings

[0037] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0038] Fig. 1: a schematic diagram of a circuit arrangement for an electric drive system, as may form the basis of an embodiment of the present invention;

[0039] Fig.2: a schematic diagram of an alternative circuit arrangement for an electric drive system, as underlying an embodiment of the present invention;

[0040] Fig. 3: a schematic representation of a block diagram of an electric drive system with a voltage converter arrangement according to an embodiment; and

[0041] Fig. 4: a flowchart underlying a method for operating a voltage converter arrangement according to an embodiment.

[0042] Description of Embodiments Figure 1 shows a schematic representation of a circuit arrangement for an electric drive system. The electric drive system comprises a voltage converter circuit 10. This voltage converter circuit 10 can be electrically coupled to an electrical energy storage device 3, for example a battery, at a DC voltage connection. For this purpose, the DC voltage connection can, for example, have two connection points to which the two poles of the electrical energy storage device 3 can be connected. Furthermore, the voltage converter circuit 10 can be electrically coupled to an AC voltage connection to an electrical machine 2. The electrical machine 2 can, for example, be a multi-phase electrical machine with, for example, three phase windings W1, W2, W3. Accordingly, the AC voltage connection can have a connection point for each phase winding W1, W2, W3.However, the present invention is not limited to three-phase electrical machines. Rather, any other multi-phase electrical machines with a number of phase windings other than three can be used.

[0043] For the operation of the electric drive system, the voltage converter circuit 10 can convert the voltage provided by the electrical energy storage device 3 into a multi-phase alternating voltage according to a setpoint specification and provide this voltage to the electric machine 2. For this purpose, the switching elements S1-S6 of the voltage converter circuit 10 can be controlled accordingly.

[0044] In a further operating mode, the voltage converter circuit 10 with the connected electrical machine 2 can be used to convert an electrical voltage from an external energy source 4 into an electrical voltage suitable for charging the energy storage device 3. In this case, the phase windings W1, W2, W3 can be used as inductive components. For this purpose, electrical energy, in particular in the form of a direct voltage, can be provided by the external energy source 4 between a motor connection and a connection point of the energy storage device 3. For this purpose, any switches that may be present between the external energy source 4 and the motor connection and a connection point of the energy storage device 3, preferably the negative connection point or the negative pole of the energy storage device 3, are preferably closed.As will be explained in more detail below, the motor connection can be either a connection to one of the phase windings or a connection to the star point of the phase windings.

[0045] In the embodiment shown in Figure 1, for example, a terminal of the external energy source 4 can be electrically coupled to a star point S of the electric machine 2. This circuit arrangement is also referred to as a W connection. The phase windings W1, W2, W3 can be energized by appropriately timing the switching elements M1-M6 of the voltage converter circuit 10. In this way, the voltage level and / or current intensity for charging the energy storage device 3 from the external energy source 4 can be adjusted.

[0046] Figure 2 shows a schematic representation of a further circuit arrangement of an electric drive system, in which the voltage converter circuit 10 and the electric machine 2 can also be used to convert the electrical voltage provided by the external energy source 4 into a voltage suitable for charging the energy storage device 3. The circuit arrangement according to Figure 2 differs from the previously described circuit arrangement in particular in that it is not the star point S of the electric machine 2 that is connected to a terminal of the external energy source 4, but rather the terminal of a phase winding W3. Such a circuit arrangement is also referred to as a Y connection.Preferably, any switches that may be present between the external energy source 4 and the motor connection and a connection point of the energy storage device 3, preferably the negative connection point or the negative pole of the energy storage device 3, are closed here as well.

[0047] Figure 3 shows a schematic representation of a block diagram for an electric drive system according to one embodiment. The electric drive system can comprise a voltage converter arrangement 1, which is electrically connected to an electric machine 2. The voltage converter arrangement 1 can comprise a voltage converter circuit 10, which converts an electrical voltage, in particular a direct voltage, provided by an electrical energy store 3 into an electrical voltage suitable for controlling the electric machine 2. This can, in particular, be one of the voltage converter circuits 10 previously described in connection with Figures 1 and 2.Accordingly, the voltage converter arrangement 1 with the voltage converter circuit 10 can also convert electrical energy from an external energy source 4 into an electrical voltage suitable for charging the energy storage device 3 in a further operating mode. For this purpose, the voltage converter circuit 10, and in particular the switching elements M1-M6 of the voltage converter circuit 10, can be controlled by a corresponding control signal from the control device 20. Furthermore, the switching elements not specified in detail in Figures 1 and 2 between the external energy source 4, the voltage converter circuit 10, and the electrical energy storage device 3 can also be opened or closed in a suitable manner depending on the operating mode.

[0048] In the operating mode for converting the input DC voltage from the external energy source 4 into an electrical voltage for charging the energy storage device 3, the phase windings Wl, W2, W3 are used as inductive components in the electric machine 2. The inductances resulting from the respective phase windings Wl, W2, W3 of the electric machine 2 can vary depending on the position of the rotor and the desired total current through the phase windings Wl, W2, W3 of the electric machine 2. Therefore, the control device 20 of the voltage converter arrangement 1 adapts the control of the voltage converter circuit 10 according to the rotor position of the electric machine 2 or the resulting inductances of the phase windings Wl, W2, W3. This results in individual current supply for each phase winding Wl, W2, W3 used, depending on the rotor position of the electric machine 2.For this purpose, for example, the current rotor position of the rotor of the electric machine 2 can be detected using a rotor position sensor 2a or resolver and provided to the control device 20. Alternatively, any other method for determining the rotor position can also be used. For example, the rotor position can also be determined or estimated using a sensorless method.

[0049] For controlling the voltage converter circuit 10, a relationship between the rotor position and parameters for controlling the voltage converter circuit 10 can be stored in the control device 20, for example. For this purpose, a memory device 21 can be provided in the control device 20, for example, which stores and provides previously determined relationships between the rotor position and the control parameters. These relationships can be provided, for example, in tabular form, e.g., in the form of a so-called lookup table or similar. Furthermore, any other options for representing the relationship between the rotor position and the control of the voltage by the circuit 10 are of course also possible. In particular, relationships by means of a formula relationship, a mathematical model, or the like are also possible.

[0050] In addition to the current rotor position, other suitable parameters can also be considered for adjusting the control of the voltage converter circuit 10. For example, the control can also be adjusted depending on the input voltage, input current, output voltage, output current, or other operating parameters such as temperature, for example, motor temperature, in particular temperatures in the phase windings or the rotor of the electric machine 2, or the like.

[0051] By adapting the control for individual current supply to the phase windings Wl, W2, W3, it is possible to adjust both the current level and the phase shift between the voltages in the individual phase windings Wl, W2, W3, which are applied to the individual phase windings Wl, W2, W3. Furthermore, it is also possible to vary the number of phase windings Wl, W2, W3 used to convert the input DC voltage into the output DC voltage, depending on requirements, for example, depending on the rotor position, the desired charging current, the voltage level, or similar. For example, depending on the operating point, only a portion of the available phase windings Wl, W2, W3 may be supplied with current.

[0052] The individual current supply for the individual phase windings Wl, W2, W3 can be set using the rotor position and, if necessary, other parameters at the start of the voltage conversion. In addition, it is also possible to dynamically adjust the current supply to the individual phase winding Wl, W2 or W3 during operation, i.e. during the voltage conversion. In this way, properties of the system which change over time can be taken into account. For example, if the output DC voltage is used to charge an electrical energy storage device 3, this output DC voltage can increase during the charging process. This can, if necessary, lead to the required parameters for the individual current supply to the phase windings Wl, W2, W3 changing over time.For this purpose, it is possible to monitor any operating parameters of the voltage transformer arrangement 1 and, if necessary, also of other components of the overall system, such as motor 2, for example by measuring them or by determining them in another way, for example by means of a mathematical model, and to determine and set optimized parameters for the current supply for the individual phase windings W1, W2, W3.

[0053] Figure 4 shows a flowchart underlying a method for operating a voltage converter arrangement 1 according to one embodiment. The voltage converter arrangement 1 can, for example, be the voltage converter arrangement 1 described above. Accordingly, all previously stated statements also apply to the method described below. Furthermore, the voltage converter arrangement 1 described above can also comprise any components that are suitable for carrying out the method described below. In a step 110, a rotor position of an electrical machine 2 connected to the voltage converter circuit 10 is first determined. Then, in step 120, the voltage converter circuit 10 can be controlled to convert an input DC voltage provided at the voltage converter circuit 10 into a predetermined output DC voltage.The voltage conversion takes place particularly when the connected electrical machine 2 is at a standstill.

[0054] During the conversion of the electrical input DC voltage into the predetermined output DC voltage, as previously described, the electrical currents through at least one phase winding W1, W2, W3 of the multi-phase electrical machine 2 connected to the voltage converter circuit 10 can be adjusted using the determined rotor position of the electrical machine 2

[0055] In summary, the present invention relates to a voltage converter arrangement in an electric drive system, which can control a connected electric machine in one operating mode and convert an input DC voltage into an output DC voltage in another operating mode. The phase windings of the connected electric machine can be used as inductors to convert the input DC voltage into the output DC voltage. The individual phase windings are individually energized depending on the rotor position and a setpoint for the total current.

Claims

Claims 1. A voltage converter arrangement (1), comprising: a voltage converter circuit (10) designed to be connected to a multi-phase electrical machine (2) and, when the electrical machine (2) is at a standstill in a first operating mode, to convert an input DC voltage provided at the voltage converter circuit (10) into a predetermined output DC voltage; and a control device (20) designed to adjust electrical currents through at least one phase winding (W1, W2, W3) of a multi-phase electrical machine (2) connected to the voltage converter circuit (10) using a rotor position of the electrical machine (2) during the conversion of the electrical input DC voltage into the predetermined output DC voltage.

2. Voltage converter arrangement (1) according to claim 1, wherein the voltage converter circuit (10) comprises a DC voltage connection and an AC voltage connection, wherein the DC voltage connection is designed to be connected to an electrical energy store (3) and the AC voltage connection is designed to be connected to the electrical machine (2), and wherein the voltage converter circuit (10) is designed, in the first operating mode, to receive the input DC voltage between a connection point of the DC voltage connection and a motor connection on the input side and to provide the output DC voltage between the first connection point and a second connection point of the DC voltage connection on the output side. The voltage converter arrangement (1) according to claim 1 or 2, wherein the control device (20) is designed to adjust electrical currents through the at least one phase winding (Wl, W2, W3) of the multi-phase electrical machine (2) connected to the voltage converter circuit (10) using a setpoint value for a total current to be adjusted. The voltage converter arrangement (1) according to one of claims 1 to 3, wherein the control device (20) is designed to determine inductance values ​​for the phase windings (Wl, W2, W3) of the multi-phase electrical machine (2) connected to the voltage converter circuit (10) using the rotor position of the electrical machine (2) and to adjust the electrical currents through the phase windings (Wl, W2, W3) of the electrical machine (2) using the determined inductance values.Voltage converter arrangement (1) according to one of claims 1 to 4, comprising a storage device (21) designed to provide data for a relationship between the rotor position of an electrical machine (2) and the electrical currents to be set in the phase windings (Wl, W2, W3) of the electrical machine (2), wherein the control device (20) is designed to read out the data stored in the storage device (21) and to set the electrical currents using the data read out from the storage device (21). Voltage converter arrangement (1) according to one of claims 1 to 5, wherein the control device (20) is designed to create a phase shift between the electrical currents through at least two phase windings (Wl, W2, W3) of the multi-phase windings connected to the voltage converter circuit (10). electrical machine (2) using a rotor position of the electrical machine (2). Voltage converter arrangement (1) according to one of claims 1 to 6, wherein the control device (20) is designed to receive a signal from a rotor angle sensor (2a) of the electrical machine (2) and to adjust the electrical currents through the phase windings (Wl, W2, W3) of the electrical machine (2) using the received signal from the rotor angle sensor (2a). Voltage converter arrangement (1) according to one of claims 1 to 7, wherein the control device (20) is designed to calculate the rotor position of the multi-phase electrical machine (2) connected to the voltage converter circuit (1) and to adjust the electrical currents through the phase windings (Wl, W2, W3) of the electrical machine (2) using the calculated rotor position.Voltage converter arrangement (1) according to one of claims 1 to 8, wherein the control device (20) is designed to adjust the electrical currents through the phase windings (W1, W2, W3) of the electrical machine (2) further using further operating parameters of the voltage converter arrangement (1) and / or of the multi-phase electrical machine (2) connected to the voltage converter circuit (10). Voltage converter arrangement (1) according to one of claims 1 to 9, wherein the voltage converter arrangement (1) is further designed to provide an electrical alternating voltage for controlling the multi-phase electrical machine (2) in a second operating mode. Electric drive system, comprising: a voltage converter arrangement (1) according to one of claims 1 to 10; and. a multiphase electrical machine (2) electrically coupled to the voltage converter assembly (1). A method for operating a voltage converter assembly (1) with a voltage converter circuit (10) designed to be connected to a multiphase electrical machine (2), comprising the steps: Determining (110) a rotor position of an electrical machine (2) connected to the voltage converter circuit (10); Controlling (120) the voltage converter circuit (10) to convert an input DC voltage provided at the voltage converter circuit (10) into a predetermined output DC voltage when the connected electrical machine (2) is at a standstill, wherein during the conversion of the electrical input DC voltage into the predetermined output DC voltage, electrical currents through at least one phase winding (W1, W2, W3) of the multi-phase electrical machine (2) connected to the voltage converter circuit (10) are set using the determined rotor position of the electrical machine (2).

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