METHOD FOR MODULATING TORQUE RIPPLE AND/OR RADIAL FORCE OF A THREE-PHASE CURRENT OPERATED ELECTRIC MACHINE

Abstract

A method for modulating a torque ripple and/or a radial force of a three-phase current-operated electric machine includes selecting at least one of a harmonic (HM1_EM) in a torque of the electric machine and a harmonic (HM_X) of a load coupled to the electric machine. The at least one selected harmonic (HM1_EM, HM_X) is modulated by applying the at least one selected harmonic (HM1_EM, HM_X) to a d-current and/or a q-current or to a variable correlated therewith in order to generate a setpoint variable for driving the electric machine A phase angle (φd,k2φqk) of at least one of a harmonic (H.sub.Id) in the d-current and harmonic (H1q) in the q-current is at least temporarily set to be different with respect to a rotor angle,such that φ.sub.d,k ≠φ.sub.q,k applies.

Claims

1. A method for modulating at least one of a torque ripple and a radial force of a three-phase current-operated electric machine, comprising: selecting at least one of a harmonic (H.sub.M1_EM) in a torque of the electric machine and a harmonic (H.sub.M_X) of a load coupled to the electric machine; wherein the at least one selected harmonic (H.sub.M1_EM, H.sub.M_X) is modulated by applying the at least one selected harmonic (H.sub.M1_EM, H.sub.M_X) to at least one of a d-current and a q-current or to a variable correlated therewith in order to generate a setpoint variable for driving the electric machine; wherein a phase angle (φ.sub.d,k, φ.sub.q,k) of at least one of a harmonic (H.sub.Id) in the d-current and a harmonic (H.sub.Iq) in the q-current is, at least temporarily, set to be different with respect to a rotor angle, such that φ.sub.d,k ≠ φ.sub.q,k applies.

2. The method according to claim 1, wherein the at least one selected harmonic is modulated such that at least one of the torque of the electric machine and a torque of the load is smoothed out to reduce vibrations and noise.

3. The method according to claim 1, wherein: at least one of the d-current and the q-current is selected in such a way that a magnitude of a resulting stator voltage $\left|u\right|=\sqrt{u_{\text{d}}^2+u_{\text{q}}^2}$ or a magnitude of the resulting stator current $\left|i\right|=\sqrt{i_{\text{d}}^2+i_{\text{q}}^2}$ is minimized, where $u_{\text{d}}=R\cdot i_{\text{d}}+\frac{\text{d}{\Psi }_{\text{d}}\left(i_{\text{d}},i_{\text{q}},\gamma \right)}{\text{d}t}-\omega {\Psi }_{\text{q}}\left(i_{\text{d}},i_{\text{q}},\gamma \right);$ and $u_{\text{q}}=R\cdot i_{\text{q}}+\frac{\text{d}{\Psi }_{\text{q}}\left(i_{\text{d}},i_{\text{q}},\gamma \right)}{\text{d}t}-\omega {\Psi }_{\text{d}}\left(i_{\text{d}},i_{\text{q}},\gamma \right).$ .

4. The method according to claim 1, further comprising calculating the harmonic in at least one of the d-current and the q-current by: modulating the torque of the electric machine to minimize the torque ripple by taking into account at least one of an induced voltage and the radial force or to minimize the radial forces by taking into account the induced voltage; generating at least one of the torque ripple and the radial forces by taking into account the induced voltage, and modulating the induced voltage by taking into account at least one of the torque ripple and the radial force.

5. The method according to claim 1, wherein, to generate the setpoint variable for driving the electric machine, the d-current, the q-current, the phase angle of the harmonic (H.sub.Id) in the d-current, and the phase angle of the harmonic (H.sub.Iq) in the q-current are read from a table.

6. The method according to claim 5, wherein the d-current, the q-current, the phase angle of the harmonic (H.sub.Id) in the d-current, and the phase angle of the harmonic (H.sub.Iq) in the q-current are read from four different tables, wherein two of the tables each contain amplitudes of d-variables and q-variables, and wherein two further tables each contain associated phases of the d-variables and the q-variables.

7. The method according to claim 5, wherein the d-current, the q-current, the phase angle of the harmonic (H.sub.Id) in the d-current, and the phase angle of the harmonic (H.sub.Iq) in the q-current are read from four different tables, wherein two of the tables each contain real amplitude values of d-variables and q-variables, and wherein two further tables each contain imaginary amplitude values of the d-variables and the q-variables.

8. The method according to claim 5, wherein some of the d-current, the q-current, the phase angle of the harmonic (H.sub.Id) in the d-current, and the phase angle of the harmonic (H.sub.Iq) in the q-current are read from a table containing variables, and some of the d-current, the q-current, the phase angle of the harmonic (H.sub.Iq) in the d-current, and the phase angle of the harmonic (H.sub.Iq) in the q-current are determined according to a predetermined rule.

9. The method according to claim 1, wherein the load is a drive train of a motor vehicle.

10. The method according to claim 1, wherein the variable correlated with the at least one of the d-current and the q-current is one of a stator voltage or a magnetic flux of the electric machine.

11. A method for modulating at least one of a torque ripple and a radial force of a three-phase current-operated electric machine, comprising: selecting at least one of a harmonic (H.sub.M1_EM) in a torque of the electric machine and a harmonic (H.sub.M_X) of a load coupled to the electric machine; modulating the at least one selected harmonic (H.sub.M1_EM, H.sub.M_X) by applying the at least one selected harmonic (H.sub.M1_EM, H.sub.M_X) to a d-current and/or to a q-current to generate dynamic input variables; setting, at least temporarily, at least one of a phase angle of a harmonic (H.sub.Id) in the d-current and a phase angle of a harmonic (H.sub.Iq) in the q-current to be different from a rotor angle; and generating setpoint variables for driving the electric machine based on the dynamic input variables.

12. The method according to claim 11, wherein the phase angle of the harmonic (H.sub.Id) in the d-current is different from the phase angle of the harmonic (H.sub.Iq) in the q-current.

13. The method according to claim 11, wherein the load is a drive train of a motor vehicle.

14. The method according to claim 11, wherein at least one of the d-current and the q-current is selected in such a way that a magnitude of a resulting stator voltage or a magnitude of a resulting stator current is minimized.

15. The method according to claim 14, wherein the magnitude of the resulting stator voltage is dependent on a speed of the electric machine and a change in a magnetic flux in the electric machine.

16. The method according to claim 15, wherein the torque of the electric machine is dependent on the magnetic flux, the d-current, and the q-current.

17. The method according to claim 11, further comprising calculating the at least one phase angle by: modulating the torque of the electric machine; minimizing the torque ripple based on at least one of an induced voltage and the radial force; generating the torque ripple based on the induced voltage; and modulating the induced voltage based on the torque ripple.

18. The method according to claim 17, further comprising calculating the at least one phase angle further by: modulating the radial force of the electric machine; minimizing the radial force based on at least one of the torque ripple and the induced voltage; generating the radial force based on the induced voltage; and modulating the induced voltage based additionally on the radial force.

19. The method according to claim 11, further comprising calculating the at least one phase angle by: modulating the radial force of the electric machine; minimizing the radial force based on at least one of the torque ripple and an induced voltage; generating the radial force based on the induced voltage; and modulating the induced voltage based on the radial force.

20. The method according to claim 11, wherein the dynamic input variables are further generated by determining at least some of the d-current, the q-current, the phase angle of the harmonic (H.sub.Id) in the d-current, and the phase angle of the harmonic (H.sub.Iq) in the q-current via a table.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Both the disclosure and the technical field are explained in more detail below with reference to the figures. It should be noted that the disclosure is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the substantive matter outlined in the figures and to combine them with other components and knowledge from the present description and/or figures. In particular, it should be noted that the figures and in particular the proportions shown are only schematic in nature. Identical reference signs indicate the same objects so that explanations from other figures can also be used.

[0019] In the drawings:

[0020] FIG. 1 shows a schematic representation of a drive train of an electrically drivable motor vehicle in a block diagram;

[0021] FIG. 2 shows, in the top representation, a torque curve of an electric machine with three different drive procedures and, in the bottom representation, voltage curves, associated with the torque curves shown in FIG. 2 above, on a stator of the correspondingly driven electric machine;

[0022] FIG. 3 shows the block diagram of a control and regulation unit from FIG. 1 in a more detailed representation;

[0023] FIG. 4 shows the block diagram of a setpoint generator from FIG. 1 in a more detailed representation;

[0024] FIG. 5 shows the block diagram of a harmonics from FIG. 4 according to the prior art and according to the disclosure in a comparison; and

[0025] FIG. 6 shows the block diagram of the setpoint generator from FIG. 4 in an expanded representation.

DETAILED DESCRIPTION

[0026] FIG. 1 shows a schematic representation of a drive train 100 of an electrically drivable motor vehicle in a block diagram. An electric machine 10 is mechanically coupled on an output side to a load 20, such as a drive axle of the motor vehicle. On an input side, the electric machine 10 is driven by a power electronics unit 30 which, for example, supplies stator windings of the electric machine 10 with three-phase current. For this purpose, the power electronics unit 30 is connected to an energy source 40, such as an onboard battery of the motor vehicle, wherein a DC voltage or direct current supplied by the battery is converted into three-phase current via corresponding inverters of the power electronics unit 30. The power electronics unit 30 is connected via a further interface on an input side thereof to a control/regulation unit 50, which drives the power electronics unit 30 in accordance with setpoint specifications of a setpoint generator 60 connected to an input side of the control/regulation unit 50. In this regard, the control/regulation unit 50 is optionally provided via corresponding sensors with operating variables, which are important for driving the electric machine 10, of the electric machine 10, of the load 20 driven by the electric machine 10, and of the energy source 40 supplying the power electronics unit 30 or electric machine 10.

[0027] In the top representation, FIG. 2 shows a torque curve of an electric machine 10 with three different drive procedures. A first torque curve M1 (solid line) shows a torque that occurs when the electric machine 10 is driven with sinusoidal excitation without harmonic components according to conventional techniques. A second torque curve M2 (dash-dotted line) shows the torque curve that occurs in the case of sinusoidal excitation with standard harmonic components according to conventional techniques. Finally, a third torque curve M3 (dotted line) shows, in comparison with this, the torque curve that occurs in the case of sinusoidal excitation with harmonic components according to the disclosure, wherein the d-variables and/or the q-variables have a phase angle that is at least temporarily different from a rotor angle.

[0028] In the bottom representation, FIG. 2 shows voltage curves, associated with the torque curves shown in FIG. 2 above, on a stator of the correspondingly driven electric machine 10. A first voltage curve U1 (solid line) shows a voltage that occurs when the electric machine 10 is driven with sinusoidal excitation without harmonic components according to conventional techniques. A second voltage curve U2 (dash-dotted line) shows the voltage curve that occurs in the case of sinusoidal excitation with standard harmonic components according to conventional techniques. Finally, a third voltage curve U3 (dotted line) shows, in comparison with this, the voltage curve that occurs in the case of sinusoidal excitation with harmonic components according to the disclosure, wherein the d-variables and/or the q-variables have a phase angle that is at least temporarily different from the rotor angle. The example shown clearly indicates that the same torque can be provided with the method according to the disclosure as with conventional methods, wherein a significantly lower voltage amplitude is required.

[0029] FIG. 3 shows the block diagram of the control/regulation unit 50 from FIG. 1 in a more detailed representation. The control/regulation unit 50 is shown with its static input variables of d-current i.sub.d0 and q-current i.sub.q0 as well as with the dynamic d and q input variables i.sub.dk(γ) and i.sub.dq(γ) that change according to the rotor angle. On the output side, the setpoint variables U.sub.a, .sub.b, .sub.c for driving the power electronics unit 30 are shown. A setpoint/actual value comparison and the corresponding regulation are possible either with an additive component or by filtering out the dynamic part in the setpoint/actual value comparison and adding it up again during the subsequent adjustment process (so-called blind addition of the dynamic part as voltage).

[0030] FIG. 4 shows the block diagram of the setpoint generator 60 for specifying setpoint values to the control/regulation unit 50 from FIG. 1 in a more detailed representation. The setpoint generator 60 shown provides the input variables for the control/regulation unit 50, which have already been explained above in relation to FIG. 3, on the output side thereof. The input variables are generated by modeling a torque request using a torque part 61, wherein a harmonic H.sub.M1_EM in the torque of the electric machine 10 and/or a harmonic H.sub.M_X of a load 20 of the drive train coupled to the electric machine 10 is/are selected. The at least one selected harmonic H.sub.M1_EM, H.sub.M_X is then modulated by applying the at least one selected harmonic H.sub.M1_EM, H.sub.M_X to the d-current and/or q-current in order to generate a setpoint variable w for driving the electric machine 10.The phase angle φ.sub.d,k, φ.sub.q,k of the harmonic H.sub.Id in the d-current Id and/or of the harmonic H.sub.Iq in the q-current Iq with respect to the rotor angle (y) is at least temporarily set to be different, such that φ.sub.d,k ≠φ.sub.q,k applies. The phase angle (relative to the rotor angle) of the current (Id, Iq) can thus be set independently of Id and Iq, so it can be set to be different if this is advantageous.

[0031] The calculation strategy on which the harmonic part 62 is based includes at least the following parts: [0032] modulation of torque and/or radial forces; [0033] minimization of the torque ripple by taking into account the induced voltage and/or the radial forces; [0034] minimization of the radial forces by taking into account the torque ripple and/or the induced voltage; [0035] generation of torque ripples and/or radial forces by taking into account the induced voltage; and [0036] modulation of the induced voltage by taking into account the torque ripple and/or the radial forces.

[0037] The harmonic part 62 optionally receives input variables externally in the form of a ripple request and internally from the torque part 61. On the output side, both the static variables i.sub.d0, i.sub.q0 as input variables for the control/regulation unit 50 and the dynamic variables i.sub.dk(γ), i.sub.dq(γ) as input variables for the control/regulation unit 50 are then provided by the setpoint generator 60 using the torque part 61.

[0038] FIG. 5 shows the block diagram of the harmonic part 62 from FIG. 4 according to the prior art (above) and according to the disclosure (below) in a comparison. It is easy to see that, according to the disclosure, the phase angles of the d-current and q-current are fundamentally different.

[0039] FIG. 6 shows the block diagram of the setpoint generator 60 from FIG. 4 in an expanded representation. The representation of the setpoint generator 60 already shown and explained in FIG. 4 is expanded in this embodiment by a corresponding table part 63, using which to generate a setpoint variable w for driving the electric machine 10, for example, the d-current Id, the q-current Iq as well as the d-phase angle φ.sub.d,k and the q-phase angle φ.sub.q,k can be read from a table.

[0040] To generate a setpoint variable w for driving the electric machine 10, variables can be read from four different tables, wherein two of the tables each contain amplitudes of d-variables and q-variables and wherein two further tables each contain the associated phases of the d-variables and the q-variables. Alternatively, in order to generate a setpoint variable w for driving the electric machine 10, variables are read from four different tables, wherein two of the tables each contain real amplitude values of d-variables and q-variables and wherein two further tables each contain imaginary amplitude values of the d-variables and the q-variables. Finally, in order to generate a setpoint variable w for driving the electric machine 10, variables can be read from a table containing in particular only amplitude variables, wherein further required variables are determined according to a predetermined rule.

[0041] The disclosure is not limited to the embodiments shown in the figures. The above description is therefore not to be regarded as restrictive, but rather as explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the disclosure. This does not exclude the presence of further features. If the patent claims and the above description define “first” and “second” features, this designation serves to distinguish between two features of the same type without defining an order of precedence.

LIST OF REFERENCE SIGNS

[0042] 10 Electric machine [0043] 20 Load (drive train) [0044] 30 Power electronics unit [0045] 40 Battery/energy source [0046] 50 Control/regulation unit [0047] 60 Setpoint generator [0048] 61 Torque part [0049] 62 Harmonic part [0050] 63 Table part [0051] 100 Drive train