Method for controlling an electric machine in an at least partially electrified vehicle in

Abstract

The invention relates to a method for controlling an electric machine (116) of an electric axle drive system (101) in an at least partially electrified vehicle (100), the electric axle drive system (101) having a converter means (121), in particular an inverter unit (118), connected upstream of the electric machine (116) for voltage conversion, the method comprising: detecting a stationary state of the vehicle (100); receiving a heat demand signal (134) of the vehicle (100) in a stationary state, the heat demand signal (134) indicating a heat demand of at least one vehicle component (120) of the vehicle (100); according to the invention, the converter mechanism (121), in particular the inverter unit (118), is actuated in order to supply the electric machine (116) with an electric current in such a way that the difference between a predetermined target value and a current value of the total thermal load is below a predetermined threshold value and the thermal load difference between the individual phases of the electric axle drive system (101) is minimized.

Description

Technical Field

[0001] The present invention relates to a method for controlling an electric motor in an at least partially electrified vehicle, a corresponding device or a corresponding controller, a corresponding electric axle drive system having the electric motor and the device, an at least partially electrified vehicle having the electric axle drive system, and a corresponding computer-readable storage medium. Background Art

[0002] Purely electric vehicles and hybrid vehicles are known in the prior art. These vehicles are driven solely by or with the support of one or more electric machines (E-machines) as drive units. To supply electrical energy to the electric machines of these electric or hybrid vehicles, they include energy storage devices, particularly rechargeable batteries or secondary batteries. While these batteries are designed as DC voltage sources, electric machines typically require AC voltage. Therefore, a so-called DC / AC inverter, employing semiconductor-based power electronics, is typically connected between the battery and the electric machine of an electric or hybrid vehicle to convert the DC input voltage into an AC output voltage for powering the electric machine.

[0003] This inverter uses a half-bridge to set a predetermined voltage on the lines or phases of an electric motor or rotating-field motor. In each half-bridge, two semiconductor-based power switches (a high-side power switch and a low-side power switch) are connected in series between different potentials of the intermediate circuit voltage. The corresponding phase of the motor is contacted at the point where the two power switches are connected. If the two power switches are alternately switched on and off with a predetermined duty cycle, for example, according to pulse-width modulation (PWM), the required, typically sinusoidal, phase voltage is generated on the phase. In this way, an AC output voltage or phase voltages that are phase-shifted relative to each other can be generated on the motor lines from the DC input voltage of the battery. These phase voltages generate a rotating stator magnetic field, which interacts with the rotor's own magnetic field, thereby driving the rotor's rotational motion.

[0004] When the motor is running, so-called copper losses occur on the motor side, and switching losses occur on the inverter side. During normal motor operation, iron losses, friction losses, and rotor copper losses also occur on the motor side. Conduction losses also occur on the inverter side, with copper losses dominating on the motor side when the stator current vector rotates slowly. The resulting heat, if not dissipated effectively, can lead to inverter overheating. At the same time, additional heat is sometimes required. For example, it is useful to pre-temperature the drive battery to optimize its functionality for the desired driving operation. Pre-temperature control is achieved by heating the drive battery until it reaches the required temperature. To increase the driving range, this pre-temperature control of the (battery) system can be performed, preferably while the vehicle is parked at a charging station or charging pile at a lower ambient temperature. In this case, the energy required for pre-temperature control does not need to be drawn from the drive battery; instead, it can be drawn directly from the charging station. Alternatively or additionally, the generated heat can be used to heat the vehicle interior.

[0005] However, motor control methods known in the prior art have a disadvantage: when phase current is fed into the motor to generate heat, the individual phases, particularly the individual coil windings of the stator and the inverter components corresponding to the individual phases, heat unevenly. This can lead to asymmetric thermal loads between the individual phases in the motor or the entire electric axle drive, potentially impairing the functionality of the electric axle drive and consequently shortening its service life. Summary of the Invention

[0006] The object of the present invention is to provide a method for controlling an electric machine in an at least partially electrified vehicle when the vehicle is stationary in order to generate the heat required for the vehicle when stationary, wherein the functionality and service life of the electric axle drive are optimized.

[0007] According to the invention, this object is achieved by a method, a device, an electric axle drive system having such a device, an at least partially electrified vehicle having an electric axle drive system, and a computer-readable storage medium according to the independent claims. Advantageous refinements and developments of the invention are given in the dependent claims.

[0008] In a first aspect, the invention relates to a method and a corresponding device for controlling an electric machine in an at least partially electrified vehicle when the vehicle is at a standstill.

[0009] The vehicle can be a pure electric vehicle or a hybrid vehicle. The vehicle's electric axle drive system includes an electric machine (E-machine), which is preferably designed as an asynchronous motor (ASM), a separately excited synchronous motor (FSM), or a current-excited synchronous motor (SSM). The motor is preferably controlled using field-oriented regulation (FOR). Field-oriented regulation can separate the components that form the magnetic field and torque, also known as the d component and the q component, wherein the detected stator variables are transformed into a rotating coordinate system (dq coordinate system).

[0010] To supply current to the electric motor (particularly its stator) having multiple coil windings, the electric axle drive system includes a converter mechanism, particularly a DC / AC inverter or inverter unit, which is connected between the drive battery (e.g., a high-voltage battery with a nominal voltage of 400V or 800V) and the electric motor. The inverter unit is therefore connected upstream of the electric motor, as viewed from the drive battery. The inverter unit is used to convert the DC input voltage provided by the drive battery into an AC output voltage. To this end, the inverter unit has an intermediate circuit (or commutation circuit) with an intermediate circuit capacitor, to which the intermediate circuit voltage is applied. The intermediate circuit capacitor can include a single capacitor or an assembly of multiple capacitor modules. In addition, the inverter unit has a phase for each coil winding of the motor stator. The inverter unit is preferably designed to be multi-phase, i.e., to have multiple phases. Each phase includes multiple semiconductor-based power switches, which form a half-bridge. The power switches can be designed as MOSFETs, IGBTs, or other designs. As the semiconductor material underlying the power switches, silicon or so-called wide bandgap semiconductors (WBS), such as silicon carbide (SiC) or gallium nitride (GaN), can be used. In each half-bridge, a high-side device (high-side power switch) consisting of one or more power switches connected in parallel and a low-side device (low-side power switch) consisting of one or more power switches connected in parallel are connected in series between different potentials of the intermediate circuit voltage. Where the high-side and low-side devices are connected to each other, the relevant phases are contacted. If the high-side power switch and the low-side power switch are alternately opened and closed with a predetermined duty cycle, the required phase voltage is generated on the phase, which is supplied to the relevant coil winding. In this way, by means of pulse width modulation (PWM) of the power switches, phase voltages that vary sinusoidally over time can be generated on the individual phases of the motor, which together form the AC output voltage.

[0011] The converter mechanism can additionally include a DC / DC converter unit (English: DC / DC Converter), which also has power electronics and is designed to supply current to the rotor of an electric machine (preferably designed as an electromagnet), the power electronics including a half-bridge assembly with power switches. The electric machine is designed, for example, as a separately excited synchronous machine or a current-excited synchronous machine. Such a DC / DC converter unit can also be used to charge the drive battery in a so-called boost configuration, wherein the same power electronics of the inverter unit can be used for this purpose.

[0012] When the vehicle is stationary, it may happen that vehicle components require heat. For example, it may be useful or necessary to pre-temperature the drive battery in order to optimize its functionality for the desired driving operation. This is achieved by heating the drive battery until it reaches the required temperature. Alternatively or additionally, it may be useful or necessary to heat the vehicle interior using a corresponding heating device.

[0013] To this end, the present invention provides a device for controlling an electric motor. The device is preferably designed as a controller, which can be a vehicle's electronic control unit (ECU), or alternatively integrated into the ECU, or even alternatively connected to the ECU via signal technology. The device is designed to perform a method or control method for an electric motor.

[0014] The method includes detecting a stationary state of the vehicle. This can be achieved by the ECU of the vehicle sending a corresponding stationary state signal to the device according to the invention, which is generated as soon as the vehicle is stationary.

[0015] The method also includes receiving a heat demand signal from a vehicle in a stationary state. The heat demand signal indicates the heat demand of a vehicle component of the vehicle. A vehicle component such as a drive battery to be pre-temperatured may be generated. For example, the heat demand signal may be generated when, for example, the monitored drive battery temperature or the external or ambient temperature (i.e., the temperature of the vehicle's surroundings) falls below a predetermined lower limit. Alternatively or additionally, at least one vehicle component may include a vehicle interior heating mechanism. In this case, the heat demand signal may be generated, for example, when the temperature of the vehicle interior falls below a predetermined temperature threshold. Alternatively or additionally, the heat demand signal may be generated after a predetermined time period has elapsed since the onset of the stationary state. The heat demand signal may be a point-in-time signal, a temporal (e.g., periodic) signal sequence, or alternatively, a temporally continuous signal. The above-mentioned configurations for the vehicle components and heat demand signal are merely exemplary and are not limiting of the present invention. The heat demand signal may be actively detected by the device according to the present invention (or the controller according to the present invention) or passively transmitted to the device or controller as a detected signal.

[0016] The converter mechanism, in particular the inverter unit, is then actuated to supply current to the electric motor. The power switches of the converter mechanism, or more precisely the inverter unit, are alternately opened and closed, generating a phase current in which the individual phases of the electric motor, in particular the stator coil windings associated with each phase (stator windings), as well as the converter mechanism or inverter unit are uniformly thermally loaded. To this end, the thermal load of each phase (on the motor side and / or the converter side or the inverter side) is preferably determined. In a first approximation, the copper losses representing the thermal load on the motor side and / or the switching losses and / or conduction losses representing the thermal load of each phase on the converter side / inverter side can be measured and / or calculated. The thermal load thus determined on the motor side and / or the inverter side can be used to determine the total thermal load of the electric axle drive system. The inverter unit is then actuated so that the total thermal load corresponds to a setpoint value. The setpoint value describes the required total thermal load of the electric axle drive system, preferably corresponding to the detected heat demand. To this end, the difference between the actual value and the setpoint value of the total thermal load can be determined. Based on the difference between the actual value and the setpoint value, the power switches of the converter mechanism or the inverter unit are switched accordingly, and the phase current is thereby adjusted until the setpoint value is reached.

[0017] Furthermore, by switching the power switches, the thermal load differences between the individual phases of the electric axle drive system (on the motor side and / or the converter side or the inverter side) can be minimized. The thermal load differences between the individual phases are determined as thermal load differences. Preferably, the thermal load differences are minimized by controlled rotation of current vectors corresponding to the phase currents of the motor in a d / q coordinate system. Further preferably, the thermal load differences are reduced to zero and maintained at zero. The minimization process is accompanied by switching the power switches according to a correspondingly appropriate switching pattern.

[0018] The heat generated by supplying current to the stator, whether in the inverter unit or in the electric motor, in particular in the stator windings, is output to at least one vehicle component in order to meet its heat requirements. For example, this heat is used to pre-temperature the drive battery. The heat transfer can take place via the coolant circuit of the electric axle drive system. In this case, the coolant present in the coolant circuit of the electric motor or converter unit (inverter unit) is heated, and its temperature subsequently rises. If the same coolant circuit is also used to cool the drive battery, or alternatively is thermally coupled to a separate coolant circuit of the drive battery via a heat exchanger, the heat generated according to the invention can also be supplied to the drive battery in order to heat the latter in a targeted manner, with the aim of pre-temperature control. This also applies analogously to the case where at least one vehicle component includes a vehicle interior heating device or another / other component to be heated.

[0019] According to the present invention, an electric axle drive system can be operated in the manner described above to achieve targeted heat generation. This can be achieved without the need for an additional heat source, facilitating a compact and power-efficient electric axle drive system. Heat generation utilizes existing components of the electric axle drive system, particularly the motor and converter mechanism, specifically the inverter unit. This allows for easy initiation of heat generation and high reliability control. Simultaneously, the stator magnetic field can be specifically regulated to maintain the torque on the rotor below a predetermined upper limit, thereby ensuring vehicle stability. This is achieved without sacrificing the lifespan of the motor and converter mechanism or inverter unit due to uneven thermal loading between phases. Furthermore, unnecessary heat use is avoided, as heat generation only begins when a heat demand signal is received. This improves the energy efficiency of the electric axle drive system and the vehicle as a whole.

[0020] According to one embodiment, the converter mechanism, in particular the inverter unit, is controlled to generate a stator magnetic field such that its rotational frequency (angular frequency) is below a predetermined first threshold frequency. This enables a low angular frequency of the generated stator magnetic field, thereby keeping the torque acting on the rotor (or the motor shaft of the electric machine) relatively low. In this case, the copper losses on the motor side occur primarily in the stator windings. Furthermore, by averaging over a period of the stator magnetic field corresponding to the angular frequency, the copper losses are essentially the same for all phases. Furthermore, this enables uniform (or symmetrical) thermal loading of the multiphase system in the electric machine and the converter mechanism, more specifically the inverter unit. This also offers a further advantage, as the stator can generally be cooled better than, for example, the rotor when stationary, particularly when using oil cooling for the electric machine, so that any copper losses in the overall system can be largely dissipated. Possible values ​​for the predetermined first threshold frequency are, for example, less than 1 Hz, preferably less than 0.5 Hz, more preferably less than 0.1 Hz, even more preferably less than 0.01 Hz, and even more preferably less than 0.005 Hz. Such a threshold frequency value (or value range) preferably also applies to the above-mentioned rotation of the current vector in the d / q coordinate system.

[0021] According to another embodiment, the converter arrangement, in particular the inverter unit, is controlled to generate an AC output voltage based on a DC input voltage. The AC output voltage corresponds to a voltage vector rotating at a second rotational frequency relative to the rotor coordinate system, wherein the second rotational frequency is below a predetermined second threshold frequency. Alternatively or additionally, the converter arrangement, in particular the inverter unit, is controlled to generate a plurality of AC output voltages based on the DC input voltage. These AC output voltages correspond to current vectors rotating at a third rotational frequency relative to the d / q coordinate system, wherein the third rotational frequency is below a predetermined third threshold frequency. The second and / or third rotational frequencies preferably correspond to or are equal to the first rotational frequency of the stator magnetic field. The second and / or third threshold frequencies preferably correspond to or are equal to the first threshold frequency. In this case, the exemplary threshold frequency values ​​(or value ranges) described above further preferably also apply to the second and / or third threshold frequencies. This also allows for improved uniformity of the thermal loads of the individual phases.

[0022] According to another preferred embodiment, the rotation of the stator magnetic field at the first rotational frequency and / or the rotation of the voltage vector at the third rotational frequency are generated directly based on the rotation of the current vector at the second rotational frequency. In particular, by regulating the phase currents on the input side of the controlled object, the second rotational frequency of the current vector can be used as a manipulated variable to generate the third rotational frequency of the voltage vector or the first rotational frequency of the stator magnetic field on the output side of the controlled object. In this case, the first and / or third rotational frequency is directly related to the second rotational frequency or is equal to the latter.

[0023] The present invention also relates to an electric axle drive system for an at least partially electrified vehicle, comprising an electric machine, a converter mechanism (in particular an inverter unit) connected upstream of the electric machine for voltage conversion, and the above-described device (controller) according to the invention. Furthermore, the present invention relates to an at least partially electrified vehicle having an electric axle drive system according to the invention, and a computer-readable (storage) medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to the invention according to any of the embodiments described herein. The advantages already described in connection with the method according to the invention also result for the device according to the invention, the electric axle drive system according to the invention, the vehicle according to the invention, and the (storage) medium according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is explained below by way of example with reference to the embodiments shown in the drawings.

[0025] Figure 1 is a schematic diagram of an electric axle drive system for an at least partially electrified vehicle, the electric axle drive system having an electric machine and a converter mechanism connected upstream of the electric machine;

[0026] Figure 2 is a schematic circuit diagram of an inverter unit that is intended to be turned on when the vehicle is stationary due to heat generated by the motor;

[0027] Figure 3 is a schematic diagram of a method of controlling a motor to generate heat when a vehicle is stationary;

[0028] Figure 4 A schematic diagram of another method of controlling a motor to generate heat when the vehicle is stationary. DETAILED DESCRIPTION

[0029] In all figures, identical objects, functional units and similar components are denoted by the same reference numerals and are identical in their technical features, unless otherwise indicated explicitly or implicitly in the description.

[0030] Figure 1 1 is a schematic diagram of an exemplary at least partially electrified vehicle 100. The vehicle 100 can be designed as a pure electric vehicle or a hybrid vehicle. The vehicle 100 has an electric axle drive system 101 with an electric motor (E-machine) 116, a converter mechanism 121 and a transmission 112. The converter mechanism 121 is connected upstream of the electric motor 116 with respect to the power transmission direction of the electric axle drive system 101 (i.e., from the drive battery 120 to the wheels 102, 104). The transmission 112 is connected downstream of the electric motor 116 with respect to the power transmission direction of the electric axle drive system 101. The transmission 112 is preferably a single-stage transmission or a reduction transmission for transmitting power from the electric motor 116, in particular from the rotor of the electric motor 116, to the wheels 102, 104.

[0031] The converter mechanism 121 has an inverter unit 118, which is designed to convert a DC input voltage U provided by the drive battery 120 into a DC input voltage U by switching a plurality of semiconductor-based power switches S1-S6 integrated in the inverter unit 118. dc Converts to an AC output voltage with multiple phase voltages. Figure 2 A schematic circuit diagram of a purely exemplary design of an inverter unit 118 is shown. The power switches S1-S6 are connected in a half-bridge topology, wherein a so-called B6 bridge topology is selected purely by way of example in the present case in order to enable a phase-to-phase converter with three phase voltages U an 、U bn 、U cn The three-phase AC output voltage is 100V. The three high-side power switches S1, S3, and S5 form the high-side components, while the three low-side power switches S2, S4, and S6 form the low-side components. The high-side components and the low-side components are connected to each other at the point where the relevant phases are contacted. If the high-side and low-side power switches S1-S6 are alternately opened and closed at a predetermined duty cycle, the required phase voltage U is generated on that phase. an 、U bn 、U cn , which is applied to the relevant coil windings of the motor 116, in particular the stator of the motor 116. In this way, by means of pulse width modulation (PWM) of the power switches S1-S6, a phase voltage U that varies sinusoidally with time can be generated in each phase of the motor 116. an 、U bn 、U cn The converter mechanism 121, more precisely the inverter unit 118, is actuated by a device 130 designed as a controller. The controller can comprise an electronic control unit (ECU) of the vehicle, or alternatively be integrated in the ECU, or alternatively be connected to the ECU via signal technology.

[0032] Device 130 is designed to carry out a method or a control method for electric axle drive system 101 . Figure 3 is a schematic diagram of a method according to one embodiment. The method is used to control motor 116 to generate heat in order to meet the thermal requirements of a vehicle component (here, for example, drive battery 120). Initially, a stationary state signal 135 indicating the stationary state of vehicle 100 is transmitted to device 130 by stationary state signal generator 133. The stationary state signal is generated after vehicle 100 has reached a stationary state. Preferably, the stationary state signal is generated only after a stable stationary state has been determined to have persisted for at least a predetermined period of time.

[0033] Device 130 also receives a heat demand signal 134 generated by a heat demand detection unit 132. Heat demand detection unit 132 is designed, for example, to monitor the temperature of drive battery 120. Alternatively or additionally, the temperature of the environment surrounding vehicle 100 and / or the temperature of the vehicle interior (for example, if vehicle component 120 includes a vehicle interior heater) may be monitored. When the monitored temperature falls below a predetermined lower limit, heat demand signal 134 may be generated and sent to device 130. Alternatively or additionally, heat demand signal 134 may be generated when vehicle 100 is restarted. Preferably, heat demand signal 134 is generated and sent to device 130 after vehicle 100 has been idle for a period of time, in particular, after a predetermined threshold has been reached between the time period from the last time vehicle 100 was idle and the time period from the time vehicle 100 was restarted. This measure serves to pre-temperature drive battery 120 before starting driving operation, so as to adjust or optimize the function of drive battery 120 for the desired driving operation. The heat demand signal 134 may be a point-in-time signal, a temporal (eg, periodic) sequence of signals, or alternatively a temporally continuous signal.

[0034] In response to the received heat demand signal 134, the device 130 generates a control signal 136 to supply current to the motor 116 in order to generate heat. To this end, the control signal 136 is input to the inverter unit 118, which then opens and / or closes the high-side power switches S1, S3, S5 and the low-side power switches S2, S4, S6 according to a switching pattern (e.g., alternately). Figure 3 In the schematically shown design, the electric machine 116 is, for example, a permanently excited synchronous machine PSM. By switching the inverter unit 118 based on the DC input voltage U dc The phase current I generated together to form the AC current signal 138 a , I b , I c is fed into the coil windings associated with the corresponding phases of the stator of the electric machine 116 (or fed into the stator windings).

[0035] Alternatively, motor 116 can be designed as a separately excited synchronous motor (FSM) (not shown in detail here). In this case, converter mechanism 121 includes, in addition to inverter unit 118, a DC / DC converter unit for supplying current to the rotor of motor 116. In response to received heat demand signal 134, device 130 generates, in addition to control signal 136 for inverter unit 118, another control signal for the DC / DC converter unit. The DC / DC converter unit accordingly generates a DC current signal based on the other control signal and feeds it into the rotor or its coil windings.

[0036] The control of the converter mechanism 121, in particular the inverter unit 118, is used to supply current to the motor 116 so that the thermal load difference between the individual phases of the electric axle drive system 101 is below a predetermined threshold value. In this case, the power switches S1-S6 of the converter mechanism 121 or the inverter unit 118 are alternately opened and closed, thereby generating a phase current that uniformly loads the individual phases with thermal load. For this purpose, the thermal load of the individual phases (motor side and / or converter side or inverter side) is preferably determined. Figure 4 As shown purely schematically and by way of example, this is achieved by a determination unit 131, which preferably determines, in particular measures and / or calculates, the copper losses present in the electric motor for the motor-side thermal load and / or the switching losses or conduction losses present in the converter mechanism 121 or the inverter unit 118 for the converter-side / inverter-side thermal load of each phase. The determination unit 131 can be integrated into the device 130 according to the present invention or alternatively be designed as a separate component. The thermal load thus determined is transmitted to the device 130. The thus determined thermal load on the motor side and / or inverter side yields the total thermal load of the electric axle drive system 101. The inverter unit 118 is then controlled so that the total thermal load corresponds to a setpoint value. The setpoint value describes the total thermal load required by the electric axle drive system 101, preferably corresponding to the detected heat demand. To this end, the difference between the actual value of the total thermal load and the setpoint value can be determined. Based on the difference between the actual value and the rated value, the power switches S1-S6 of the converter mechanism 121 or the inverter unit 118 are switched accordingly, and the phase current I is adjusted accordingly. a , I b , I c , until the rated value is reached.

[0037] Furthermore, by switching the power switches S1-S6, the thermal load difference between the individual phases of the electric axle drive system 101 (on the motor side and / or the converter side or the inverter side) is minimized. As the thermal load difference, the thermal load difference between the individual phases is determined. Preferably, the thermal load difference is determined by the phase current I a , I b , I cThe corresponding controlled rotation of the current vector in the d / q coordinate system minimizes this thermal load difference, further preferably reducing it to zero and maintaining it at zero. The minimization process involves switching the power switches S1-S6 according to the corresponding appropriate switching pattern.

[0038] The switching pattern of power switches S1-S6 is selected such that the rotational frequency (angular frequency) of the generated stator magnetic field is below a predetermined first threshold frequency. This enables a low angular frequency of the generated stator magnetic field, thereby controlling the torque acting on the rotor (or the motor shaft of motor 116) to a relatively low level. Furthermore, this enables uniform (or symmetrical) thermal loading of the multiphase system in motor 116 and in converter mechanism 121 or inverter unit 118. Motor-side copper losses occur primarily in the stator windings. This offers a further advantage because the stator, when stationary, can generally be cooled better than, for example, the rotor, particularly when oil cooling of motor 116 is employed. Consequently, copper losses present in the overall system can be largely dissipated. Contemplated values ​​for the predetermined first threshold frequency are, for example, less than 1 Hz, preferably less than 0.5 Hz, more preferably less than 0.1 Hz, even more preferably less than 0.01 Hz, and even more preferably less than 0.005 Hz.

[0039] Alternatively or additionally, the converter device 121, in particular the inverter unit 118, can be controlled so as to generate a DC input voltage U dc Generate AC output voltage (phase voltage U an 、U bn 、U cn ), the AC output voltage corresponds to a voltage vector rotating at a second rotation frequency relative to the rotor coordinate system, wherein the second rotation frequency is lower than a predetermined second threshold frequency.

[0040] Alternatively or additionally, the converter device 121, in particular the inverter unit 118, can be controlled so as to generate a DC input voltage U dc Generates AC phase current I a , I b , I c , these AC phase currents correspond to current vectors rotating at a third rotation frequency relative to the d / q coordinate system, wherein the third rotation frequency is lower than a predetermined third threshold frequency.

[0041] By supplying electric motor 116 with current, heat generated in converter mechanism 121 or in electric motor 116 itself, particularly in the stator and rotor windings, is transferred to at least one vehicle component or drive battery 120 to meet their thermal requirements. For example, this heat is used to pre-temperature drive battery 120. Heat transfer can occur via the coolant circuit of electric axle drive system 101. In this case, the coolant present in the coolant circuit of electric motor 116 or converter mechanism 121 is heated, subsequently increasing its temperature. If the same coolant circuit also serves to cool drive battery 120, or alternatively is thermally coupled to a separate coolant circuit of drive battery 120 via a heat exchanger, the heat generated according to the present invention can be supplied to drive battery 120, just as during cooling, for targeted heating of the latter for pre-temperature control. This also applies similarly if at least one vehicle component 120 includes a vehicle interior heating mechanism or another component to be heated.

[0042] List of Reference Numerals

[0043] 100 vehicles

[0044] 101 Electric Axle Drive System

[0045] 102 and 104 wheels

[0046] 112 Transmission

[0047] 116 Motor

[0048] 118 Inverter Unit

[0049] 120 vehicle components (drive battery)

[0050] 121 converter mechanism

[0051] 130 device (controller)

[0052] 131 Determine Unit

[0053] 132 Heat demand detection unit

[0054] 133 Static State Signal Generator

[0055] 134 Heat demand signal

[0056] 135 Static state signal

[0057] 136 control signals

[0058] 137 Heat Load

[0059] 138 AC current signal

[0060] Udc DC input voltage

[0061] U an 、U bn 、U cn Phase voltage

[0062] S1-S6 power switches

[0063] I a , I b , I c Phase current.

Claims

1. A method for controlling an electric motor (116) of an electric axle drive system (101) in an at least partially electrified vehicle (100), wherein: The electric axle drive system (101) has a converter mechanism (121), in particular an inverter unit (118), connected upstream of the electric machine (116) for voltage conversion, and the method comprises: - detecting a stationary state of the vehicle (100); - receiving a heat demand signal (134) of the vehicle (100) in the stationary state, wherein the heat demand signal (134) indicates a heat demand of at least one vehicle component (120) of the vehicle (100); - operating the converter mechanism (121), in particular the inverter unit (118), so as to supply current to the electric machine (116) so that the total thermal load of the electric axle drive system (101) corresponds to a predetermined rated value and the thermal load differences between the individual phases of the electric axle drive system (101) are minimized.

2. The method according to claim 1, wherein The method further includes: - Determine the thermal load of the individual phases on the motor side and / or converter side or inverter side; - regulating the total thermal load with a predetermined rated value by switching a plurality of power switches of the converter mechanism (121) or the inverter unit (118); As the thermal load difference, determining the difference between the determined thermal loads of the individual phases on the motor side and / or on the converter side or on the inverter side; By means of a controlled rotation of the current vector corresponding to the phase current of the electric machine in the d / q coordinate system, the thermal load difference is minimized, in particular reduced to zero.

3. The method according to claim 2, wherein: The copper loss of each phase is measured and / or calculated for the thermal load on the motor side; and / or the switching loss and / or conduction loss of each phase is measured and / or calculated for the thermal load on the converter side / inverter side.

4. A method according to any one of the preceding claims, wherein The converter mechanism (121), in particular the inverter unit (118), is controlled to generate a stator magnetic field having a first rotation frequency that is lower than a predetermined first threshold frequency.

5. The method according to claim 4, wherein The first threshold frequency is less than 1 Hz, preferably less than 0.5 Hz, more preferably less than 0.1 Hz, even more preferably less than 0.01 Hz, even more preferably less than 0.005 Hz.

6. A method according to any one of the preceding claims, wherein The converter mechanism (121), in particular the inverter unit (118), is controlled to generate an AC output voltage based on a DC input voltage, the AC output voltage corresponding to a voltage vector rotating at a second rotation frequency relative to a rotor coordinate system, wherein the second rotation frequency is lower than a predetermined second threshold frequency.

7. A method according to any one of the preceding claims, wherein The converter mechanism (121), in particular the inverter unit (118), is controlled to generate a plurality of AC phase currents based on a DC input voltage, the plurality of AC phase currents corresponding to current vectors rotating at a third rotation frequency relative to a d / q coordinate system, wherein the third rotation frequency is lower than a predetermined third threshold frequency.

8. A method according to any one of the preceding claims, wherein The invention also includes supplying heat generated when current is supplied to the motor (116) to the at least one vehicle component (120), wherein the at least one vehicle component preferably includes a drive battery and / or a vehicle interior heating mechanism.

9. A device (130), in particular a controller, for controlling an electric motor (116) of an electric axle drive system (101) in an at least partially electrified vehicle (100), wherein: The electric axle drive system (101) has a converter mechanism (121), in particular an inverter unit (118), connected upstream of the electric machine (116) for voltage conversion, wherein the device (130) is designed to carry out the method according to any one of claims 1 to 8.

10. An electric axle drive system (101) for an at least partially electrified vehicle (100), comprising: - an electric motor (116); - a converter mechanism (121), in particular an inverter unit (118), connected upstream of the electric machine (116) for voltage conversion; - The device (130) according to claim 9.

11. An at least partially electrified vehicle (100) having an electric axle drive system (101) according to claim 10.

12. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform the steps of the method according to any one of claims 1 to 8.

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