METHOD AND DEVICE FOR REGULATING AN ELECTRIC MACHINE

Description

[0001] The invention relates to a method and a device for controlling an electric machine. Furthermore, the invention relates to an electric drive system with a corresponding device and a vehicle with an electric drive system, as well as a computer program and a computer-readable storage medium. State of the art

[0002] The documents US 2002 / 097015 A1, US 2006 / 038531 A1, US 2013 / 193898 A1 and DE 10 2018 202967 A1 disclose methods and devices for controlling an electrical machine.

[0003] German patent application DE 2017 102 036 91 A1 discloses a control system for an electric machine in which a disturbance variable is simultaneously compensated and a setpoint is set. For the operation of the electric machine, a phase current is set as the setpoint. The phase current is preferably set as a sinusoidal fundamental wave. During operation of the electric machine, the phase current causes the output of a uniform average torque. Due to non-ideally sinusoidal magnetic fields, winding arrangements, slotting, tooth geometry, saturation effects, and / or other effects, harmonic overtones of the torque are generated in addition to the uniform average torque. Such effects lead to force waves between the rotor and stator, which, at characteristic orders, act on the stator teeth as tangential and radial tooth forces.Due to the mechanical transmission characteristics of the electric machine, these forces are perceived as vibrations in the machine, the machine housing, and coupled components, and thus as structure-borne and airborne noise or surface vibrations. The harmonic overtones of the torque also cause harmonics of the electric machine's electrical frequency to appear on the phase current as disturbances. To minimize these disturbances, specific harmonics are introduced and superimposed on the regulated and predetermined phase current.

[0004] There is a need for alternative methods and devices for controlling an electrical machine, with which the harmonics can be controlled as robustly, stably, dynamically and flexibly as possible to take relevant frequency components into account. Disclosure of the invention

[0005] The invention is defined by the features of the independent claims.

[0006] A method for controlling an electric machine with a harmonic controller is provided, wherein the harmonic controller comprises an input transformation, a controller, and an output transformation. The method includes the following steps: Determining a feedback variable, wherein the feedback variable comprises an actual value of a harmonic of a given frequency in a field-oriented system; transforming the feedback variable by means of the input transformation to a direct feedback variable in a harmonic-oriented system; determining a control deviation as the difference between a predefined computational variable and the direct feedback variable in the harmonic-oriented system; determining a control variable by means of the controller as a function of the control deviation; transforming the control variable back into a manipulated variable in the field-oriented system by means of the output transformation; energizing at least one winding of the electrical machine as a function of the manipulated variable.

[0007] Field-oriented control systems are widely used to regulate electrical machines. In these systems, the alternating quantities of the phase currents to be regulated in the time domain, preferably sinusoidal, also called fundamental frequencies, are transformed mathematically into a coordinate system that rotates at the frequency of the alternating quantities. The frequency of the alternating quantities also determines the frequency of the magnetic field in the machine, so this coordinate system rotating at the frequency of the alternating quantities is also called a field-oriented system. In steady-state operation of the electrical machine, the alternating quantities in the time domain result in DC quantities in the field-oriented system, which can be controlled using standard control engineering methods. The field-oriented system is also called a d / q coordinate system. Its d-axis points in the direction of the rotor flux, and the q-axis is perpendicular to the d-axis.A sinusoidal phase current is represented as a stator current vector, characterized by its length and direction. This current vector rotates synchronously with the rotating stator or rotor flux of the electric machine. In the d / q coordinate system, the current vector can be represented by two mutually perpendicular components, Id and Iq, which are DC quantities in the steady state.

[0008] To control an electrical machine that can be connected to or is connected to the harmonic controller, a feedback signal from the electrical machine is acquired in the field-oriented system. This feedback signal includes a harmonic superimposed on the phase current through the electrical machine. In the field-oriented system, the phase current is a DC quantity, whereas the harmonic is an AC quantity. Therefore, to control the harmonic, a further mathematical transformation is performed, similar to the transformation from the time domain to the field-oriented domain, using a harmonic frequency from the field-oriented system to a harmonic-oriented system. For this purpose, the feedback signal is transformed into a DC feedback signal in the harmonic-oriented system by means of an input transformation.Quantities represented as AC quantities in the field-oriented system are represented as DC quantities in the harmonic-oriented system during steady-state operation of the electrical machine. These can be controlled using standard control engineering methods. Accordingly, a control deviation is determined as the difference between a predefined computational variable and the feedback variable in the harmonic-oriented system. A control variable is then calculated as a function of the control deviation. This computational variable, as a DC quantity in the harmonic-oriented system, is transformed back into a manipulated variable in the field-oriented system for further use in the field-oriented control of the electrical machine via the output transformation. In the field-oriented system, the manipulated variable comprises an AC quantity, a harmonic.Finally, the procedure includes a step to energize the electrical machine depending on the manipulated variable.

[0009] Advantageously, a method for an effective harmonic controller is provided.

[0010] The formulation that a control loop variable includes a harmonic or a fundamental frequency means, within the scope of this application, that a control loop variable characterizes or describes at least one harmonic or fundamental frequency, whereby the respective control loop variable may also include further signal components, for example, fundamental frequency and one or more harmonics, as well as any additional disturbances present.

[0011] For the control of electrical machines, target phase currents are commonly specified based on measured actual phase currents, depending on a torque specification, with phase voltages being set as manipulated variables. Consequently, preferably within the scope of this application, the feedback variable (Idq), the DC feedback variable (IHrmc), the DC control variable (IHrmc*), the machine feedback variable (labc), or the predefinable DC control variable (Idq*) each comprise a current value, and / or the DC control variable (UHrmc*), the manipulated variable (UdqHrmc*), the DC control variable, or the machine manipulated variable (Uabc*) each comprise a voltage value.

[0012] In another embodiment of the invention, the feedback variable in the field-oriented system comprises a harmonic with a positive frequency with a first amplitude and a first phase of a k-th order of an electrical frequency of the electrical machine and / or a harmonic with a negative frequency with a second amplitude and a second phase of the k-th order of an electrical frequency of the electrical machine.

[0013] The feedback variable in the field-oriented system includes at least one harmonic. With respect to the electrical frequency of the electrical machine, the harmonic(s) have a positive and / or negative frequency of the kth order, with a respective amplitude and phase. One order that represents a relevant disturbance variable, since its amplitudes are particularly large, is, for example, the 6th order, preferably in the positive and negative directions. For example, with an electrical frequency of the electrical machine, i.e., the fundamental frequency, of 450 Hz in the time domain, the frequency of the 6th order is 450 Hz + 450 Hz * 6 = 3150 Hz, and in the negative direction, it is 450 Hz - 6 * 450 Hz = -2250 Hz. In the field-oriented system, whose coordinate system rotates with the electrical frequency of the electrical machine, the electrical frequency of the electrical machine is mapped to 0 Hz, resulting in frequencies of +2700 Hz and -2700 Hz for the harmonics of the 6th order.Depending on the magnitude of the amplitudes and the phase angle, force waves arise between the rotor and stator of the electric machine. These force waves act on the stator teeth as tangential and radial tooth forces, causing the harmonic overtones of the torque. The more relevant orders of the feedback variables are considered for the control system, the more effectively the disturbances are corrected.

[0014] Advantageously, a feedback variable is provided for effective harmonic control.

[0015] In another embodiment of the invention, the feedback variable is transformed as a function of a determined current rotor angle of the electric machine and comprises a rotation with a rotation angle corresponding to k times the current rotor angle. The rotation is performed in a positive and / or negative direction.

[0016] The transformation from the field-oriented system to the harmonic-oriented system involves a rotation using a rotation matrix. An alternating quantity in the field-oriented system thus becomes a direct quantity in the harmonic-oriented system. For this purpose, the feedback variable is rotated by an angle corresponding to k times the current rotor angle; that is, for the transformation of the 6th-order harmonic of the electrical frequency, by 6 times the current rotor angle. For the kth-order harmonics in the positive direction, the rotation is in the positive direction; for the kth-order harmonics in the negative direction, the rotation is in the negative direction. The resulting direct quantities in the harmonic-oriented system can be characterized or described using complex numbers or as complex parameters, e.g., as iPosReal, iPoslmag, or as iNegReal and iNeglmag.

[0017] Besides rotation, other transformations can also be used. For example, the complex components iDSin and IDCos can be calculated by multiplying the d-current with the sine function (depending on the k-fold rotor angle) and with the cosine function, and the complex components iQSin and IQCos can be calculated by multiplying the q-current with the sine function and with the cosine function (also called frequency mixing or heterodyning).

[0018] Another alternative description can be complex harmonics with amplitude and phase of the d-current and q-current respectively.

[0019] The proportions can also be represented as an ellipse with height, width, rotation and phase by superimposing two counter-rotating pointers with different amplitude and phase, preferably for particularly efficient calibration.

[0020] Advantageously, transformations are provided to supply DC quantities, enabling effective harmonic control.

[0021] In another embodiment of the invention, the predefinable equalization parameter of the harmonic-oriented system comprises a setpoint parameter in the harmonic-oriented system for generating a harmonic on a sinusoidal phase current for energizing at least one winding of the electrical machine.

[0022] The equalization variable is a setpoint for generating a harmonic of a predefined frequency or k-th order of the electrical frequency of the electric machine. This harmonic is superimposed on the sinusoidal phase current or the fundamental frequency used to energize the electric machine. This setpoint is specified analytically or using a characteristic map, particularly as a function of a torque specification, a (phase) current setpoint, an actual current value, or a determined phase current. For use in the harmonic controller in a harmonic-oriented system, it is pre-transformed accordingly.

[0023] Advantageously, a common reference value is provided for effective harmonic control.

[0024] The determination of the equalization variable using the controller is carried out depending on the control deviation by means of a control system, with a PI or I controller, an inverse static or dynamic model and a PI or I controller or a controller with an inverse static or dynamic model.

[0025] When using a PI or I controller, separate controllers are used for each harmonic current component, for example iPosReal, iPoslmag, iNegReal and / or iNeglmag.

[0026] When using an inverse static or dynamic model and a PI or I controller, control deviations or current deviations are converted into voltage deviations using the inverse model. Subsequently, separate PI or I controllers are used for each harmonic voltage component, such as uPos-Real, uPoslmag, uNegReal, and / or uNeglmag. The model is calculated from a d / q model or field-oriented model of the electrical machine. The model can be statically designed or can also incorporate dynamic components. Control using a model that considers dynamic components is more accurate and allows for higher controller dynamics.

[0027] When using a controller with an inverse model (known as an IMC controller (internal model control) or CVD controller (complex vector design)), the inverse controller corresponds to the inverse model of the controlled system multiplied by an integrator. For a closed-loop control system T, the following applies: T = ω BW ω BW + s T = GK 1 + GK K = ω BW sG

[0028] The variables represent the following quantities: G: Machine model K: Controller model T: Closed control loop ω BW : Bandwidth s: Laplace

[0029] The individual components, e.g., iPosReal, iPoslmag, iNegReal, and iNeglmag, are no longer controlled separately. Only the cutoff frequency of the desired low-pass behavior of the closed-loop control system is specified.

[0030] Since this controller results in a low-pass filter response in the closed-loop system, adding another low-pass filter to the loop is not advisable. Even with this approach, a control model that incorporates dynamic components is more accurate.

[0031] Advantageously, different controllers are provided for effective harmonic control.

[0032] In another embodiment of the invention, the feedback variable is inverted as a function of a determined current rotor angle of the electric machine. The inverted transformation comprises a rotation with an angle of rotation corresponding to k times the current rotor angle. The inverted transformation includes a rotation in the positive and / or negative opposite direction to the rotation of the feedback variable by means of the input transformation.

[0033] The transformation from the harmonic-oriented system to the field-oriented system involves a rotation using a rotation matrix. A DC quantity in the harmonic-oriented system thus becomes an AC quantity in the field-oriented system. For this purpose, the DC quantity is rotated by an angle corresponding to k times the current rotor angle; that is, when transforming the 6th-order harmonic of the electrical frequency, by 6 times the current rotor angle. For the kth-order harmonics in the positive direction, the rotation is in the positive direction; for the kth-order harmonics in the negative direction, the rotation is in the negative direction. Preferably, for rotations in both the negative and positive directions, the resulting AC quantities in the field-oriented system are added together to form the manipulated quantity.

[0034] In addition to rotation, other transformations, as described above, can also be used.

[0035] Advantageously, back-transformations are provided to supply alternating quantities that can be further used for effective fundamental frequency control.

[0036] In another embodiment of the method for controlling an electric machine, it further comprises a fundamental frequency controller, wherein the fundamental frequency controller includes a fundamental frequency input transformation, a fundamental frequency controller, and a fundamental frequency output transformation. The method further comprises the following steps: determining a machine feedback variable, wherein the machine feedback variable comprises an actual value of the electric machine; Transforming the machine feedback variable to the feedback variable in the field-oriented system using the gateway input transformation; determining the gateway control deviation as the difference between a predefined gateway equalization variable and the feedback variable in the field-oriented system; determining a gateway equalization variable using the gateway controller as a function of the gateway control deviation; superimposing the gateway equalization variable with the manipulated variable; inversely transforming the output variable of the superposition to a machine manipulated variable using the gateway output transformation and energizing at least one winding of the electrical machine as a function of the machine manipulated variable.

[0037] In addition to harmonic control, the control system includes fundamental frequency control. Fundamental frequency control regulates the alternating quantities of the phase currents, preferably sinusoidal, which are to be regulated in the time domain. To control an electric machine that can be connected to or linked with the fundamental frequency controller, a machine feedback variable, an actual value, from the electric machine is acquired in the time domain. The machine feedback variables are preferably the phase currents of an electric machine. This machine feedback variable comprises the phase current as the fundamental frequency and, as disturbances, harmonics that are superimposed on the phase current through the electric machine. In the time domain, the phase current is an alternating quantity superimposed with further alternating quantities of harmonics. To control the fundamental frequency, a transformation from the time domain to the field-oriented domain is performed.For this purpose, the machine feedback variable is transformed to the feedback variable in the field-oriented system by means of a feedback input transformation. Preferably, "feedback" in this application denotes the control steps and transformations used for controlling the fundamental frequency. In steady-state operation of the electrical machine, AC quantities in the time domain result in DC quantities in the field-oriented system. These can be controlled using conventional control engineering methods. Accordingly, a feedback control deviation is determined as the difference between a predefined feedback equalization variable and the feedback variable in the field-oriented system. A feedback equalization variable is determined as a function of the feedback control deviation by means of a feedback controller. The manipulated variable, as the output signal of the harmonic controller, is superimposed or added to the feedback equalization variable in the field-oriented system.This output variable from the superposition in the field-oriented system is transformed back into a machine control variable in the time domain using the GW output transformation for further use in controlling or energizing the electric machine in the time domain. In the time domain, the machine control variable comprises an AC quantity, a fundamental frequency, and at least one further superimposed AC quantity, a harmonic. Finally, the method includes a step for energizing the electric machine depending on the machine control variable.

[0038] Advantageously, a method for an effective fundamental and harmonic controller is provided.

[0039] In another embodiment of the invention, the predefinable GW equalization variable of the field-oriented system comprises a setpoint for generating the fundamental wave of a sinusoidal phase current for energizing at least one winding of the electrical machine.

[0040] The fundamental wave comparator is a setpoint for generating a fundamental wave with the electrical frequency of the electric machine for powering the electric machine. This setpoint is specified analytically or by means of a characteristic map, in particular as a function of a torque specification, a (phase) current setpoint, or an actual current value, preferably a determined phase current. For use in the fundamental wave controller in the field-oriented system, it is already appropriately transformed before being specified.

[0041] Advantageously, a GW equalization parameter is provided for effective fundamental frequency control.

[0042] Furthermore, the invention relates to a computer program which includes instructions which, when executed by a computer, cause it to perform the steps of the method described so far.

[0043] Furthermore, the invention relates to a computer-readable storage medium comprising instructions which, when executed by a computer, cause it to perform the steps of the method described so far.

[0044] Furthermore, the invention relates to a device for controlling an electric machine, comprising a processing unit and a harmonic controller, wherein the harmonic controller includes an input transformation, a controller, and an output transformation. The device is configured to perform the steps of the described method.

[0045] Advantageously, a device for effective harmonic control of an electric machine is provided.

[0046] In another embodiment of the invention, the device comprises a fundamental frequency controller, wherein the fundamental frequency controller includes a fundamental frequency input transformation, a fundamental frequency controller, and a fundamental frequency output transformation. The device is configured to perform the steps of the described method.

[0047] Advantageously, a device for effective, combined fundamental and harmonic control of an electric machine is provided.

[0048] Furthermore, the invention relates to an electric drive system comprising an electric machine and a described device. Such an electric drive system serves, for example, to power an electric vehicle. The method and the device enable optimized operation of the drive train.

[0049] Furthermore, the invention relates to a vehicle with a described drive system. Advantageously, a vehicle is thus provided which includes a device with which an electric machine is effectively controlled.

[0050] It is understood that the features, properties and advantages of the method according to the invention apply accordingly to the device or drive system and the vehicle and vice versa.

[0051] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Brief description of the drawing

[0052] The invention will be explained in more detail below using some figures, including: Figure 1 a schematic control structure of a harmonic controller Figure 2 a schematic control structure for controlling an electrical machine Figure 3A schematically represented flowchart for a method for controlling an electrical machine. Figure 4 a schematically depicted device for controlling an electric machine Figure 5 a schematically represented vehicle with an electric drive system Embodiments of the invention

[0053] The Figure 1Figure 1 shows a schematic control structure of a harmonic controller 100, which comprises an input transformation 110, a controller 120, and an output transformation 130. A determined feedback variable Idq in a field-oriented system is transformed by the input transformation 110 into a direct feedback variable IHrmc in a harmonic-oriented system. A determined difference between a predefined direct feedback variable IHrmc* and the direct feedback variable IHrmc in the harmonic-oriented system is fed to the controller 120 as a control deviation and input variable. The controller 120 determines a direct input variable UHrmc* as a function of the control deviation. This direct input variable UHrmc* in the harmonic-oriented system is transformed by the output transformation 130 into a manipulated variable UdqHrmc* in the field-oriented system.Preferably, at least one winding of an electrical machine 190 is energized depending on the control variable UdqHrmc*.

[0054] The Figure 2Figure 1 shows a schematic control structure for controlling an electric machine 190. The electric machine 190 is depicted as a unit consisting of an inverter 192 and an electric motor 194. The fundamental frequency controller 200 comprises a fundamental frequency input transformation 210, a fundamental frequency controller 220, and a fundamental frequency output transformation 230. A machine feedback variable labc of the electric machine is determined in the time domain and fed to the fundamental frequency input transformation 210. The machine feedback variable labc is transformed into the feedback variable Idq in the field-oriented system by means of the fundamental frequency input transformation 210. A fundamental frequency control deviation is determined as the difference between a predefined fundamental frequency control variable Idq* and the feedback variable (Idq) in the field-oriented system. A fundamental frequency control variable is determined by means of the fundamental frequency control deviation using the fundamental frequency controller 220. As shown in Figure 1The manipulated variable UdqHrmc* is determined in parallel using the harmonic controller 100. The ground wave equalization variable is superimposed on the manipulated variable UdqHrmc*. The output of the superposition in the field-oriented system is transformed into a machine manipulated variable Uabc* in the time domain using the ground wave output transformation 230. The machine manipulated variable Uabc*, preferably a phase voltage, is provided to the electric machine 190 to energize at least one winding. The phase voltage is generated by the inverter 192 and applied to at least one winding of the electric motor 194.

[0055] The Figure 3Figure 400 shows a schematic flowchart for a method 400 for controlling an electric machine 190. The method begins with step 401. Preferably, in step 402, a machine feedback variable labc of the electric machine is determined in the time domain. Preferably, in step 404, this machine feedback variable labc is transformed into the feedback variable Idq in the field-oriented system using the feedback input transformation 210. Preferably, in step 406, a feedback control deviation is determined as the difference between a predefinable feedback control variable Idq* and the feedback variable (Idq) in the field-oriented system. Preferably, in step 408, a feedback control variable is determined as a function of the feedback control deviation using the feedback controller 220.

[0056] In step 410, a feedback variable Idq is determined and, in step 420, transformed into a direct feedback variable IHrmc in a harmonic-oriented system by means of the input transformation 110. In step 430, the difference between a predefined direct feedback variable IHrmc* and the direct feedback variable IHrmc is fed to the controller 120 as the control deviation and input variable. In step 440, a control variable UHrmc* is determined by the controller as a function of the control deviation. In step 450, this control variable UHrmc* in the harmonic-oriented system is transformed into a manipulated variable UdqHrmc* in the field-oriented system by means of the output transformation. Preferably, in step 480, at least one winding of an electrical machine 190 is energized as a function of the manipulated variable UdqHrmc*.

[0057] Preferably, in step 460, the gate control variable is superimposed with the manipulated variable UdqHrmc*. Preferably, in step 470, the output variable of the superposition in the field-oriented system is transformed into a machine manipulated variable Uabc* in the time domain using the gate control output transformation 230. Preferably, in step 480, at least one winding of the electrical machine 190 is energized depending on the machine manipulated variable Uabc*. The method ends with step 490.

[0058] The Figure 4Figure 1 shows a schematic representation of a device 300 for controlling an electric machine 190. The electric machine 190 is depicted as a unit consisting of an inverter 192 and an electric motor 194. The device 300 comprises a harmonic controller 100 and a processing unit 310 for controlling and implementing the structure of the harmonic controller 100. The device preferably includes a fundamental frequency controller 200, which is also controlled and implemented by means of the processing unit 310. The device is configured to perform the process steps described above and thus to operate and control the electric machine 190.

[0059] The Figure 5Figure 1 shows a schematic representation of a vehicle 600, which includes an electric drive system 500. The drive system 500 comprises the electric machine 190, which includes an inverter 192 and an electric motor 194, and a device 300 for controlling the electric machine, as shown in Figure 2. Figure 4 described. Preferably, the electric drive system comprises a battery for supplying the electric drive system 500 with electrical energy.

Claims

1. Method (400) for controlling an electric machine (190) having a harmonic controller (100), the harmonic controller comprising an input transformer (110), a controller (120) and an output transformer (130), comprising the steps of: ascertaining (410) a feedback variable (Idq) of the electric machine, the feedback variable comprising an actual variable of a harmonic of a specified frequency in a field-oriented system; transforming (420) the feedback variable (Idq) by means of the input transformer (110) to form a DC feedback variable (IHrmc) in a harmonic-oriented system; ascertaining (430) a control deviation as the difference between a specifiable DC reference variable (IHrmc*) and the DC feedback variable (IHrmc) in the harmonic-oriented system; ascertaining (440) a DC manipulated variable (UHrmc*) by means of the controller (120) as a function of the control deviation; back-transforming (450) the DC manipulated variable (UHrmc*) by means of the output transformer to form a manipulated variable (UdqHrmc*) in the field-oriented system; energizing (480) at least one winding of the electric machine (190) as a function of the manipulated variable (UdqHrmc*), wherein the DC manipulated variable (UHrmc*) is ascertained (440) by means of the controller (120) as a function of the control deviation by means of a control operation, using: an inverse static or dynamic model and a PI or I controller or a controller with an inverse static or dynamic model, characterized in that, when the inverse model is used, control deviations or current deviations are converted into voltage deviations using the inverse model.

2. Method according to Claim 1, wherein the feedback variable (Idq) in the field-oriented system comprises a harmonic with a positive frequency with a first amplitude and a first phase of a kth order of an electrical frequency of the electric machine (190) and / or a harmonic with a negative frequency with a second amplitude and a second phase of the kth order of an electrical frequency of the electric machine (190).

3. Method according to Claim 2, wherein transforming (420) the feedback variable (Idq) is performed as a function of an ascertained current rotor angle (w) of the electric machine (190), and transforming (420) comprises rotation with a rotation angle which corresponds to k times the current rotor angle (w), and the rotation (420) is executed in the positive direction and / or the negative direction.

4. Method according to one of the preceding claims, wherein the specifiable DC reference variable (IHrmc*) of the harmonic-oriented system comprises a target value in the harmonic-oriented system, for generating a harmonic on a sinusoidal phase current for energizing at least one winding of the electric machine (190).

5. Method according to Claim 1, wherein the DC manipulated variable (UHrmc*) is back-transformed (450) as a function of an ascertained current rotor angle (w) of the electric machine (190), and back-transforming (450) comprises rotation with a rotation angle which corresponds to k times the current rotor angle (w), and back-transforming (450) respectively comprises rotation in the positive and / or negative opposite direction to the rotation of the feedback variable (Idq) by means of the input transformer (110).

6. Method according to Claim 1, having a fundamental controller (200), the fundamental controller comprising a fundamental input transformer (210), a fundamental controller (220) and a fundamental output transformer (230), comprising the steps of: ascertaining (402) a machine feedback variable (labc), the machine feedback variable comprising an actual variable of the electric machine; transforming (404) the machine feedback variable (labc) by means of the fundamental input transformer (210) to form the feedback variable (Idq) in the field-oriented system; ascertaining (406) the fundamental control deviation as the difference between a specifiable fundamental DC reference variable (Idq*) and the feedback variable (Idq) in the field-oriented system; ascertaining (408) a fundamental DC manipulated variable by means of the fundamental controller (220) as a function of the fundamental control deviation; superimposing (460) the fundamental DC manipulated variable with the manipulated variable (UdqHrmc*); back-transforming (470) the output variable of the superimposition by means of the fundamental output transformer (230) to form a machine manipulated variable (Uabc*), and energizing (480) at least one winding of the electric machine (190) as a function of the machine manipulated variable (Uabc*).

7. Method according to Claim 6, wherein the specifiable fundamental DC reference variable (Idq*) of the field-oriented system comprises a target variable for generating the fundamental of a sinusoidal phase current for energizing at least one winding of the electric machine (190).

8. Computer program, comprising commands which, when the program is executed by a device according to Claim 10, cause said device to execute the method / the steps of the method according to Claims 1 to 7.

9. Computer-readable storage medium, comprising commands which, when executed by a device according to Claim 10, cause said device to execute the method / the steps of the method according to Claims 1 to 7.

10. Device (300) for controlling an electric machine (190), comprising a computer unit (310) and a harmonic controller (100), the harmonic controller comprising an input transformer (110), a controller (120) and an output transformer (130), wherein the device is designed to execute the steps of the method according to one of Claims 1-5.

11. Device (300) according to Claim 10, comprising a fundamental controller (200), the fundamental controller comprising a fundamental input transformer (210), a fundamental controller (220) and a fundamental output transformer (230), wherein the device is designed to execute the steps of the method according to either of Claims 6-7.

12. Electric drive system (500) comprising an electric machine (190) and a device (300) according to either of Claims 10 to 11.

13. Vehicle (600) comprising an electric drive system (500) according to Claim 12.