Targeted generation of thermal output in a vehicle drive during traction operation

Abstract

The invention relates to a method for generating a thermal output during driving operation of an electric vehicle drive. Windings (W1-W3) of an electric machine of the drive, which are connected between a first inverter (IN1) and a second inverter (IN2), are energised. For this purpose, a rotating-field-generating signal (ld,q) is used. The energisation provides that, in addition to the rotating-field-generating signal (ld,q), a current signal (IW) is generated in the windings (W1-W3). The current signal (IW) is generated in accordance with a setpoint (WS) for the thermal output. The invention also relates to a corresponding control device and to an electric traction vehicle drive.

Description

[0001] Description

[0002] Targeted generation of heat power in a vehicle drive system during operation

[0003] Traction driving operation

[0004] It is common practice to equip vehicles with an electric drive powered by a battery. Typically, the traction drive is operated in such a way that the battery's energy is converted into traction power as efficiently as possible. This also means that as little waste heat as possible is generated. While combustion engines inherently generate large amounts of heat, in electric vehicles, which lack a combustion engine, heat is generated electrically, for example, by heating elements. Especially at low ambient temperatures, electric vehicles without combustion engines must therefore convert large amounts of electrical energy into heat, which in turn requires heating elements with high power ratings.

[0005] It is an object of the invention to demonstrate a possible method for generating heat with relatively little effort. This object is achieved by the method according to claim 1. Further properties, features, embodiments and advantages will become apparent from the dependent claims, the description and the figure.

[0006] It is proposed that, in addition to the rotating field-generating signal in the windings (to generate a desired torque at a desired speed), an additional current signal be generated in the windings, which is generated according to a desired heat output (setpoint of the heat output). This allows the inverter and the windings, or even the battery, to generate additional heat in a targeted manner. The current signal is generated in addition to the rotating field-generating signal in the windings. The term "in addition" here means simultaneously or at least temporarily overlapping. This makes it possible to generate a desired heat output during ferry operation, for example, for conditioning or...Temperature control of the battery is used to achieve a desired temperature-related operating point, or to generate heat in the windings and inverters. This heat can then be used, for example, to cool the vehicle's interior via a heat recovery circuit. This can, for instance, supplement the heat generated by an air conditioning system. Furthermore, heat can be generated within the battery itself, and this heat can be transferred, at least partially, into the interior via a battery cooling circuit. Additionally, heat can be generated within the battery to warm itself, for example, at low ambient temperatures or when the battery is cold. The heating method proposed here is internal, which is significantly more efficient than external heating.The rotating field-generating signal and the current signal are power signals, in particular with a current of at least 10 A or at least 50 A (referring to the rotating field-generating signal) or with at least 1 A, at least 5 A or at least 15 A (referring to the current signal), for example at a voltage of more than 60 V, at least 200 V, at least 400 V or at least 800 V. The current signal preferably generates at least 200 W, at least 500 W, at least 1 kW or at least 5 kW of heat power.

[0007] The current signal, generated according to the desired heat output, preferably produces no or only a negligible torque in the electric machine and thus has essentially no influence on the ferry's operation. A first and a second inverter are used, between which the windings of the electric machine are connected. This makes it possible, in particular, to generate the desired current signal in the windings according to a setpoint of the desired heat output, without this current signal generating a (significant) component of the torque. Rather, the torque, or more generally, the movement of the electric machine, is caused entirely or essentially entirely by the rotating field-generating signal. Each of the two inverters has an AC side with phase connections, with each winding being connected between two phase connections of different inverters.One end of the windings is connected to the AC side of the first inverter, while the opposite end is connected to the AC side of the second inverter. Since the windings are not connected to each other via a star connection or in a delta configuration, this type of winding is also referred to as an "open-end winding." Due to the multiple inverters, in addition to the signal generating the rotating field, the desired current signal for generating heat output can also be applied (simultaneously) to the windings, thus generating both the desired rotating field and the desired heat output simultaneously.

[0008] A method for generating heat during the operation of an electric vehicle drive is described. The method involves energizing the windings of an electric motor of the vehicle drive. The electric motor is preferably an asynchronous motor or a synchronous motor, such as a permanent magnet synchronous motor or a separately excited synchronous motor. The windings are connected between a first inverter and a second inverter. In particular, the AC sides of the inverters, or the phase terminals of the inverters, are connected to opposite ends of the windings. The windings are thus connected between the inverters, or rather, between their AC sides. The number of windings corresponds to the number of phases of the first inverter and the number of phases of the second inverter.For each winding, each inverter has a half-bridge, the ends of which are connected to a supply potential (such as a battery), and whose connection point is connected to a winding end.

[0009] The inverters are operated collectively to generate the rotating field signal in the windings. This signal is generated, for example, by means of field-oriented control or vector control, similar to ferry operation. As is known, after inverse transformation of the vector representation of the control system, a pulse-width modulated signal is obtained, which is used to operate the inverters. By controlling the inverters, a rotating magnetic field is generated according to the field-oriented control system, which the rotor follows. The windings are preferably located in a stator and can also be referred to as stator windings. Input variables for the field-oriented control system are, in particular, a target speed and a target torque, which are used as setpoints in the control system to generate a corresponding rotating field-generating current signal in the windings.It is intended that, in addition to the rotating field-generating signal (current signal), a current signal for generating the desired heat output in the windings is also generated. Both signals are generated simultaneously in the windings. The two signals can be considered components of a single current signal. The current signal can also be referred to as the heat-generating current signal; the rotating field-generating signal can also be referred to as the rotating field-generating current signal.

[0010] It is intended that a (heat-generating) current signal is generated in the windings, in addition to the rotating field-generating signal. This additional current signal serves to generate heat, or a (desired or specified) heat output. The current signal is generated according to a setpoint that represents the desired heat output. The setpoint corresponding to the desired heat output can be the output of a temperature controller or a temperature regulator that regulates according to a target temperature. The controller and the regulator use the setpoint, which represents the heat output to be generated, as their reference input.

[0011] The current signal can be a DC signal, have a frequency below the (PWM) switching frequency of the rotating field-generating signal, or be equal to or greater than this switching frequency. In particular, the current signal can have a major frequency component that is below the frequency of the rotating field-generating signal corresponding to the rotational speed of the rotating field-generating signal, or that is equal to or greater than this frequency.

[0012] In specific embodiments, the current signal used for heat generation has a frequency below the (PWM) switching frequency of the rotating field-generating signal. The switching frequency is the frequency at which the pulse-width modulated pulses are emitted. In further embodiments, the current signal used for heat generation has a frequency below a rotating field-related frequency of the field-generating signal, i.e., below a frequency corresponding to the rotational speed of the electric machine. Specifically, the frequency of the current signal used for heat generation is no more than 25%, 10%, 5%, or 1% of the frequency at which the pulse-width modulated pulses are emitted, or the frequency corresponding to the rotational speed of the electric machine. However, the frequency of the current signal used for heat generation can also be higher than or equal to these frequency values.

[0013] This applies in particular to the main spectral component of the current signal, which serves (exclusively) to generate heat.

[0014] Preferred embodiments provide that the PWM pulsing of the current signal (carrier frequency) primarily generates losses in the windings and inverter. The desired heating of the battery (target heat output to be generated in the battery) is generated by modulating this carrier frequency. The frequency of this modulation (i.e., the frequency of the envelope) generates the desired heating in the battery; the pulsing frequency generates the desired heating in the windings and inverter (i.e., target heat output to be generated in the windings and inverter). If heat output is to be generated (primarily) in the windings and inverter, then the modulation is reduced, in particular to zero.

[0015] The current signal used for heat generation is, in particular, a pulsed signal, such as a signal pulsed according to a clock frequency, for example, a pulse-width modulated signal. The signal pulsed according to the clock frequency can be configured according to a desired envelope. In other words, the signal pulsed according to the clock frequency can serve as a carrier signal for a desired envelope signal. The envelope signal is generated by the configuration of the pulses (especially their duty cycle) of the pulsed signal. The envelope signal is generated, in particular, by modulating the pulsed signal; the modulation is preferably carried out by modulating / variing the pulse width or duty cycle of the pulsed signal. The signal resulting from modulating the pulsed signal can be called the envelope signal. The current signal corresponds, in particular, to the envelope signal.The spectral properties of the current signal result from the pulsing as well as from the modulation that is generated with this pulsing.

[0016] The current signal is therefore generated by pulse-width modulation (PWM), with the frequency(ies) used primarily serving to generate heat in the windings and / or inverter. The frequency(ies) used to pulse the current signal are determined according to a target heat output to be generated in the windings and / or inverter. The modulation of the current signal pulse (i.e., modulation of the duty cycle or pulse width) is performed according to a target heat output to be generated in the accumulator. The envelope signal resulting from the modulation is generated according to the target heat output with which the accumulator is heated. The spectral characteristics (especially the fundamental frequency) of the modulation, or the envelope resulting from the modulation, are determined according to the target heat output to be generated in the accumulator.The spectral characteristics (especially the fundamental frequency) of the pulsing or pulsed signal are determined according to the target heat output to be generated in the windings or the inverter. The fundamental frequency of the pulsing or pulsed signal (e.g., the pulsing repetition frequency) is preferably higher than the fundamental frequency of the envelope or modulation.

[0017] The clock frequency can, in particular, form the fundamental frequency of the current signal's frequency spectrum. The clock frequency of the signal constitutes the main spectral component, with further spectral components being generated by pulsing or clocking. The clock frequency can depend, in particular, on whether the primary or exclusive goal is to generate heat in the accumulator, or whether the primary or exclusive goal is to generate heat in the windings and the inverter. The clock frequency is selected based on the desired heat output to be generated in the windings or the inverter. Modulation using this clock frequency results in an envelope signal whose shape and spectral properties (such as the modulation fundamental frequency) are determined according to the desired heat output to be generated in the accumulator.While the rotating field-generating signal is an alternating current signal, synthesized particularly as a multiphase sine wave using pulse-width modulation, the heat-generating signal (current signal) is a direct current signal, or a pulsed direct current or alternating current signal with a frequency significantly lower than the rotational speed. The main spectral component of the pulsed direct current or alternating current signal constituting the current signal is, in some implementations, not above 20 Hz, 10 Hz, or 5 Hz, but can also be higher than or equal to these frequencies. In many embodiments, the clock frequency of the heat-generating current signal is lower than the clock frequency of the pulse-width modulated signal that characterizes the rotating field-generating signal.Furthermore, in numerous embodiments, the clock frequency of the heat-generating current signal is lower than the rotational speed of the rotating field characterized by the rotating field-generating signal (especially at speeds above a minimum speed). This is not the case in other embodiments.

[0018] The current signal (i.e., the signal used for heat generation) is defined as the common component of the current signal across all windings. Specifically, the current signal is the sum of all components of the current signal flowing through the individual windings. The current signal (used for heat generation) is given in particular as IW = ILI + IL2 + 11_3 + ... + ILn, where L1, L2, ..., Ln are the indices of the individual windings or phases of the inverter / electrical machine, and n represents the number of phases or windings. In embodiments with a normalized current signal, the current signal is given as IW = 1 / n * (IL1 + IL2 + IL3 + ... + ILn). Normalization factors other than 1 / n can also be used.

[0019] The torque component generated by the current signal is essentially negligible. This is particularly the case if it is no more than 1% of the torque generated by energizing the rotating-field-generating current signal. Preferably, the target torque component generated by the current signal is zero, particularly if the torques generated by the individual windings cancel each other out.

[0020] The current signal is generated in particular by means of a control or regulation procedure that provides a target torque component of zero for the current signal.

[0021] Several embodiments provide for the generation of the current signal by means of a control or regulation method that uses the setpoint of the heat power generated in the inverters, the windings, or a battery as a reference variable. This refers to the battery that supplies the inverters. Thus, the inverters and the windings can be used to convert the current signal into heat, or the battery can be used to convert the current signal into heat. The heat is therefore generated as power loss in the inverter at and in the winding. Furthermore, the heat can be generated as power loss in the battery that supplies the inverters with DC current. This refers in particular to a battery that is connected to the DC sides of the two inverters to supply them.This refers in particular to the accumulator, whose poles are connected to the ends of the inverter's half-bridges.

[0022] First embodiments relate to heat generation in the accumulator. In these embodiments, the current signal is generated according to the setpoint of the heat output to be generated in the accumulator. The setpoint thus refers to the heat output to be generated in the accumulator, with a control method implementing this setpoint (as far as possible). Preferably, the current signal (i.e., the current signal used for heat generation) is generated with a frequency and / or with a phase shift between the individual current components in the windings. The frequency and / or phase shift relates to an alternating component of the current supplied by the accumulator to the inverters, or more generally, the current flowing between the accumulator and the inverters. This relates in particular to the supply voltage or the supply current supplied by the accumulator.The frequency and / or phase shift can be a reference parameter for regulating or controlling the heat output generated or intended to be generated in the accumulator. The frequency and / or phase shift result from the control system, which operates according to the setpoint that represents the desired heat output to be generated in the accumulator. Thus, the frequency or phase shift is determined by the control system, which aims to generate the desired heat output (setpoint) in the accumulator using the current signal.

[0023] This results in an additionally increased current in the battery, generated by the inverters. The two inverters can also be referred to together as a dual inverter. The additional battery current can flow between the inverter and the battery at a low frequency without itself generating any torque in the electric machine (via the windings) or causing a change in the torque (generated by the rotating field signal). This is achieved, in particular, by means of a DC component in all phases of the machine, i.e., in all windings. The DC component can be provided as a pulsating DC current. The DC component of the current signal can be generated at a specific frequency or phase such that it results in a desired AC component in the current flowing between the battery and the inverters.The alternating current (AC) component arises primarily from the pulsing of the direct current (DC). The AC component used for heat generation can also be referred to as the ripple current of the accumulator. The DC component is the sum of all DC components in the individual windings. The DC component (of all windings) does not generate torque. Due to the energizing of the windings by means of two inverters connected to the winding ends, an additional degree of freedom is achieved, which can be generated independently of the signal that creates the rotating field. This is not possible with a star or delta connection of the windings, as the windings cannot be individually controlled without an undesired balancing current occurring across the connection between the windings (via the star point or the delta points), which would negate this degree of freedom.The control variables used to define the current signal or to represent the heat output (according to the setpoint) include the frequency of the current signal and / or the phase shift between the components of the current signal in the individual windings and / or the phase angle (power factor) of the current signal. Another aspect involves using these control variables to configure the components of the current signal in the individual windings in such a way that they do not generate any torque when combined.

[0024] It can thus be provided that the current signal in the windings is generated with a frequency and / or a phase shift between the windings, whereby the frequency and / or phase shift is linked to a desired current with an alternating component. The desired current is, in particular, the current (supply current) that flows between the battery and the inverters (especially their DC side). The current is linked to the target value of the heat output generated in the battery, particularly due to the heating effects resulting from alternating components in the battery current. This allows the current in the individual windings to be controlled by switching the inverters in such a way that a ripple current (current with an alternating component; the AC component of a pulsating DC current) results in the battery, leading to the desired heat output (according to the target value) in the battery.The heat generated in the battery is primarily used to maintain the battery at a temperature within a predetermined range. This temperature range is specifically defined above a temperature range where the battery's performance is limited, or where high battery output would lead to accelerated aging (compared to the same usage within the temperature range). The heat can also be used to supply the passenger compartment via a temperature control system.

[0025] The inverters and windings, on the one hand, and the accumulator that supplies the inverters, on the other, can be heated individually according to the desired heat output. Two separate, corresponding target heat outputs can be specified, or a target weighting can be defined between the two heat outputs: one for the windings and inverters on the one hand, and the other for the accumulator (which supplies the inverters) on the other. These target values ​​are used to control the generation of the current signal in order to maintain the target heat outputs. The current signal can be generated according to a first heat output target value and a second heat output target value. The first heat output target value defines the heat output to be generated in the inverters and windings.The second heat output setpoint defines the heat output to be generated in the battery that supplies the inverters. Alternatively, the weighting between the two setpoints can be specified to heat the inverters and windings on the one hand, and the battery on the other, according to individual requirements. The current signal can be generated according to a weighting. This weighting indicates what proportion of the heat output is to be generated in the inverters and windings, and what proportion is to be generated in the battery that supplies the inverters. Components of different frequencies can be generated as the heat-generating current signal, with the different proportions having varying effects on the heat output generated in the inverters and windings, and on the heat output generated in the respective battery.A first frequency can contribute more to heat generation in the inverter and windings than to heat generation in the battery, and at a second frequency this can be reversed (or a different distribution of heat generation can result). This allows several components to be weighted differently to achieve different distributions of heat generation between the battery on the one hand and the inverters / windings on the other.

[0026] Another aspect is the targeted generation of heat in the windings and the inverter. The resulting heat can be supplied to the passenger compartment, particularly as part of a passenger compartment temperature control system. This allows for the use of other, lower-powered heat generators. It is proposed to generate the current signal according to the setpoint of the heat output, which refers to the heat output generated in the inverters and windings. The aim is specifically to generate heat in the inverters and / or windings through targeted ripple (i.e., an AC component resulting from pulsing a DC current) or through a targeted DC current. These currents, specifically generated to produce the heat output (according to the setpoint), are designed and distributed across the windings in such a way that they do not result in any additional torque.Preferably, the current signal in the individual windings is generated with a frequency and / or a phase shift between the resulting current components in the windings, which leads to a current in the inverters and / or in the windings that results in the desired (additional) heat output. The desired heat output depends on the setpoint of the heat output generated in the inverters and / or in the windings. Therefore, the frequency, the phase shift between the current signal components in the windings, or the phase shift between the current and voltage of the current signal components in the windings can be used as the control variable for generating the desired heat output.Furthermore, in particular, these control variables can be used to design the current signal components in the windings in such a way that no additional torque (or at least no significant torque) is generated in the electric machine by these current signal components.

[0027] The method is preferably implemented using a high-voltage traction battery as the accumulator, the accumulator preferably belonging to a vehicle powertrain or vehicle. The inverters are preferably of the same design. The inverters are preferably traction inverters of a vehicle powertrain or vehicle and are particularly designed as high-voltage inverters. The electric machine is particularly a high-voltage electric motor; the windings are designed accordingly. The inverters and the electric machine are particularly power components with a rated power of at least 10 kW, 100 kW, or more. The prefix "high voltage" means a rated voltage of more than 60 V, at least 200 V, at least 400 V, or at least 800 V for the component in question.

[0028] Furthermore, implementation in a control device is possible. This device can be configured using a processor or controller on which a computer program can run, executing at least parts of the described method. The control device is configured to output a control signal to two inverters (as previously described), between which windings (as previously described) of an electric machine (as previously described) of an electric vehicle drive (as previously described) are connected. The control device is thus configured to drive a dual inverter to generate a rotating magnetic field in or by means of the windings connected between the two inverters of the dual inverter. The control device is configured to execute the method described here. The control device has inputs for receiving a target torque and a target rotational speed.The control device also has an input configured to receive the setpoint for heat output described herein. The control device has an output for transmitting an inverter control signal. The control device is designed to generate the control signal in such a way that it produces the rotating field-generating signal and the current signal. The rotating field-generating signal can be generated in a known manner by means of a motor control (field control, space vector-based control) implemented in the control device. The current signal, or the signal components intended for its generation, is generated in the manner described herein.The control device can be multi-part or hierarchically structured, so that the parts of the control device that generate the current signal and the rotating field signal can be different and, for example, controlled by a higher-level control device part (or one part controls another). The control device is configured to cause the inverters to generate the rotating field signal and the current signal in the windings. The inputs can be configured as one or more electrical interfaces. The inputs can also be configured as memory cells into which a value (the input value) is stored and from which it is read, for example, within the context of program modules and their variable passing.

[0029] Furthermore, an electric traction vehicle drive (as described above) can be provided with an electric machine (as described above), two inverters (as described above) between which the windings (as described above) of the electric machine are connected, and the control device (as described above). The control device is connected to the inverters to output the inverter control signal to the inverters, for example via driver circuits.

[0030] Figure 1 serves to illustrate the mode of operation of exemplary embodiments of the procedure described here.

[0031] Figure 1 shows an electric traction vehicle drive AN to illustrate the embodiments presented here. The vehicle drive AN is connected to a battery A. A DC link capacitor K, which is part of the vehicle drive AN, is connected downstream of the battery A. The drive AN further comprises two inverters IN1 and IN2, as well as an electric machine EM with three windings W1, W2, and W3. The windings W1, W2, and W3 are connected between the two inverters IN1 and IN2.

[0032] Each inverter IN1 and IN2 comprises three phases, or three half-bridges. Each half-bridge is equipped with two semiconductor switches connected in series. The semiconductor switches 1-6 and 11-16 are shown in Fig. 1 as IGBTs by way of example, although MOSFETs are also possible. The junction point in each half-bridge serves to connect one phase of the electric machine EM, i.e., to connect one end of a winding W1, W2, or W3. The windings have open ends, so each winding end is connected to a half-bridge or its junction point. Each inverter IN1 and IN2 is configured as a B6C bridge and thus has three high-side switches and three low-side switches. The high-side switches of the first inverter IN1 are designated 1, 3, and 5, while the low-side switches of inverter IN2 are designated 2, 4, and 6.This results in a first half-bridge with transistors 1 and 2, a second half-bridge with transistors 3 and 4, and a third half-bridge with transistors 5 and 6. The high-side switches of the second inverter IN2 are designated 11, 13, and 15, while the low-side switches of inverter IN2 are designated 12, 14, and 16. This results in a first half-bridge with transistors 11 and 12, a second half-bridge with transistors 13 and 14, and a third half-bridge with transistors 15 and 16. Since the ends of windings W1, B2, and B3 are open ends connected to individual inverters IN1 and IN2, respectively, the degree of freedom arises that, in addition to generating a rotating field-generating signal (signal ld,q), which is produced, for example, by means of field control, another current component or current (the current signal IW) can be superimposed in the windings.The current signal IW can be generated in the inverter and thus also (due to a feedback effect from the inverters on the accumulator) in accumulator A. The current signal IW generates heat output (according to the setpoint WS) in the windings W1-W3, in the inverters IN1 and IN2, or also in accumulator A.

[0033] A control device C generates a control signal for inverters IN1 and IN2 in the form of a pulse-width modulated (PWM) signal. For this purpose, the control device C receives a target torque T and a target speed n. From this, the control device C generates a corresponding PWM control signal, for example, within the framework of motor control. The configuration of this PWM signal depends not only on the target torque T and target speed n and the corresponding control or regulation for generating a rotating magnetic field signal ld,q in the windings W1-W3, but also on the target heat output WS. Therefore, the control device C also receives a target value WS, which relates to the heat output generated by the current signal IW in the respective component.

[0034] The value IW indicates the additional heat output to be generated by the current signal IW in windings W1-W3, inverters IN1 and IN2, and / or battery A. For this purpose, an additional component in the PWM control signal is used to generate a corresponding direct current, pulsed direct current, or a (low-frequency) alternating current component as the current signal IW in inverters IN1 and IN2. The current signal IW generates heat output in windings W1-W3 and in the electric machine EM due to ohmic losses or magnetization losses. Heat output is generated in inverters IN1 and IN2 through switching operations and / or ohmic losses. In battery A, heat (i.e., heat output corresponding to signal WS) is generated primarily by ripple currents, i.e., by (low-frequency) alternating current components, whereby these ripple currents or alternating current components are part of or correspond to the current signal IW.The target signal, which represents the heat output to be generated, is specified, for example, by a temperature control or temperature regulation system. This can be for the purpose of temperature control in a passenger compartment, or it can be specified, for example, by a battery management system for conditioning a battery.

[0035] In particular, the value WS may originate from a battery management system which, at a battery temperature below a limit temperature, initiates (additional) heating of the battery A by means of the current signal IW, which is not carried out at temperatures above this or above another, higher limit temperature.

[0036] The individual currents flowing in windings W1-W3 are represented as I1, I2, and I3. It is further shown that the currents flowing through the windings are composed of the current signal IW (which serves for heating) and the rotating field-generating signal ld,q. The individual currents flowing in the windings, which together form the current signal IW, sum to produce the desired direct current, pulsed direct current, or (low-frequency) alternating current, which is initiated by the signal WS. In particular, it is possible to specify the desired direct current, pulsed direct current, or (low-frequency) alternating current using WS and distribute it across the multiple windings or phases of the inverter to obtain the desired signal in total.

[0037] Especially with pulsed direct current in the current signal IW, the feedback from inverters IN1 and IN2 on battery A results in a ripple current that heats the battery internally. Therefore, the current signal IW also affects battery A, as heat is generated there as well. The current signal IW is designed to generate heat in battery AK with a frequency or spectrum that results in a lower current flow in the intermediate circuit capacitor K than in battery A.

[0038] In particular, the AC characteristics of the current signal IW are designed such that they neither lead to torque generation in the electric machine EM, nor are the torque generation by the rotating field-generating signal ld,q (significantly) influenced by the current signal IW. The influence or torque generation by the signal IW is particularly insignificant if the signal IW itself does not generate any additional torque and does not influence the torque generation of the signal ld,q, or if the torque generated by the signal IW is less than 1% or less than 0.1% of the torque generated by the signal ld,q.

[0039] A target value can be specified for the heat output of the current signal to be generated in windings W1, W2, W3 and / or in inverters IN1, IN2, as well as a further target value for the heat output of the current signal that it causes in the battery. Taking into account the heat output generated by different current signals in the various components (electric machine, windings, inverter, and battery), different current signals can be provided that, with the same total heat output, generate different heat outputs in the battery compared to the heat output in the windings and / or the inverter. This allows the focus of the heat output to be controlled, i.e., the heat output generated by the current signal in the battery on the one hand and in the windings / inverters on the other.

Claims

Patent claims 1. Method for generating heat output during ferry operation of an electric vehicle drive comprising the following steps: Currenting windings (W1 - W3) of an electric machine of the drive, which are connected between a first inverter (IN1 ) and a second inverter (IN2), by means of a rotating field-generating signal (ld,q), wherein the currenting includes: Generating a current signal (IW) in the windings (W1 - W3), in addition to the rotating field-generating signal (ld,q), wherein the current signal (IW) is generated according to a setpoint (WS) of the heat output.

2. Method according to claim 1, wherein the current signal (IW) is provided as a common component in all windings (W1 - W3) flowing in the individual windings (W1 - W3).

3. Method according to any of the preceding claims, wherein the torque component generated by the current signal (IW) is not more than 1% of a torque generated by the current energizing (Id, q), or wherein the current signal (IW) is generated by means of a control or regulation method which has a target torque component of zero generated by the current signal (IW).

4. Method according to any of the preceding claims, wherein the current signal (IW) is generated by means of a control or regulation method which uses as a reference variable the setpoint (WS) of the heat power generated in the inverters, in the windings (IN1 , IN2) or in an accumulator (A) which supplies the inverters (11 , I2).

5. Method according to claim 4, wherein the current signal (IW) is generated according to the setpoint (WS) of the heat power generated in the accumulator (A).

6. Method according to claim 5, wherein the current signal (IW) in the windings (W1 - W3) is generated with a frequency and a phase shift between the windings (W1 - W3) which is associated with an alternating component in the current flowing between the accumulator (A) and the inverters (IN1 , IN2) which corresponds to the setpoint (WS) of the heat power thereby generated in the accumulator (A).

7. Method according to claim 4, wherein the current signal (IW) is generated according to the setpoint (WS) of the heat power generated in the inverters (IN1 , IN2) and the windings (W1 - W3).

8. Method according to claim 7, wherein the current signal (IW) in the windings (W1 - W3) is generated with a frequency and a phase shift between the windings (W1 - W3) which is related to a current flowing in the inverters (IN1 ) and the windings (W1 - W3) which corresponds to the setpoint (WS) of the heat power generated thereby in the inverters (IN1 ) and the windings (W1 - W3).

9. A method according to any of the preceding claims, wherein the current signal is generated according to a first heat output setpoint and according to a second heat output setpoint, wherein the first heat output setpoint defines the heat output to be generated in the inverters and in the windings (IN1, IN2), and the second heat output setpoint defines the heat output to be generated in the accumulator (A) that supplies the inverters (11, I2), or wherein the current signal is generated according to a weighting, wherein the weighting indicates what proportion of a heat output is to be generated in the inverters (11, I2) and in the windings (IN1, IN2), and what proportion of the heat output is to be generated in the accumulator (A) that supplies the inverters (11, I2).

10. Control device (C) configured to output a control signal (PWM) for two inverters (IN1, IN2) between which windings (W1 - W3) of an electric machine (EM) of an electric vehicle drive are connected, wherein the control device is configured to execute the The method is set up according to one of the preceding claims and, in addition to inputs for receiving a target torque (T) and a target speed (n), has an input for receiving the target value (WS) of the heat output, and has an output for supplying an inverter control signal (PWM) that causes the inverters (IN1 , IN2) to generate the rotating field-generating signal (ld,q) and the current signal (IW) in the windings (W1 - W3).

11. Electric traction vehicle drive with an electric machine (EM), two inverters (IN1 , IN2) between which the windings (W1 - W3) of the electric machine (EM) are connected, and the control device (C) according to claim 10, which is connected to the inverters (IN1 , IN2) for the purpose of supplying the inverter control signal (PWM) to the inverters (IN1 , IN2).

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