Control unit, drive train, method for operating a drive train and motor vehicle

Abstract

The present invention provides a control unit (1) for generating PWM pulses for an inverter (2), in particular for an inverter (2) of a drive train (10), the control unit having a noise reduction device (3) for generating an anti-signal for active noise reduction, wherein the noise reduction device (3) is adapted to set the phase (ΔθPWM) of the anti-signal according to a predefined PWM frequency (F) and / or rotational speed (ωm). The present invention also provides a drive train (10), a motor vehicle (100) and a method for operating a drive train (10).

Description

Field of the Invention

[0001] The present invention relates to a control unit for generating PWM pulses for an inverter, in particular an inverter of a drive train, a drive train having an electric machine, a method for operating the drive train, and a motor vehicle. Background Art

[0002] An electric machine in a motor vehicle is typically supplied with three-phase alternating current, i.e., three phase currents. To supply the electric machine with phase currents, an inverter provides an alternating voltage for generating the phase currents. Here, the alternating voltage is generated by the inverter from a direct voltage provided by an energy storage device.

[0003] To convert the direct voltage into an alternating voltage, the inverter typically has fast-switching semiconductor switches. By means of these semiconductor switches, the desired amplitude and frequency of the phase currents are set.

[0004] Here, for example, the semiconductor switches are controlled by pulse width modulation (PWM). Here, the PWM frequency of the inverter is typically selected such that the total losses of the inverter and the electric machine are minimized depending on the operating point.

[0005] To improve the driving comfort of a motor vehicle having an electric machine, it is meaningful to reduce noise. In addition to sound insulation measures, measures for active noise reduction are also taken. It is known from the prior art, for example, that an anti-signal is generated and processed during the control of the semiconductor switches for noise reduction. Here, the anti-signal is typically determined for a pre-given, fixed PWM frequency. However, in practice, when the PWM frequency changes, the noise reduction deteriorates or even the noise increases. Summary of the Invention

[0006] Therefore, an object of the present invention is to provide a control unit for generating PWM pulses for an inverter, which does not have the disadvantages mentioned in the prior art, but can achieve improved and reliable noise reduction.

[0007] This object is achieved by a control unit for generating PWM pulses for an inverter, in particular an inverter of a drive train, the control unit having a noise reduction device for generating an anti-signal for active noise reduction, wherein the noise reduction device is adapted to set the phase of the anti-signal according to a pre-given PWM frequency.

[0008] By means of an anti-signal, additional forces are generated in an electric machine in a targeted manner with respect to the tangential and radial forces generated. It has surprisingly been shown that if the anti-signal is only tuned to the PWM frequency, a deviation from the optimal phase results when the PWM frequency changes. The forces generated in the electric machine are no longer exactly anti-phase with the existing higher-order tangential and radial forces, whereby these forces are therefore not completely eliminated or are even increased. This is corrected by setting the phase of the anti-signal and ensuring the anti-phase of the forces, torque fluctuations and thus the sound waves and reverse sound waves.

[0009] Advantageous configurations and refinements of the invention can be derived from the preferred embodiments and the description with reference to the drawings.

[0010] According to a preferred embodiment of the invention, it is proposed that the noise reduction device is adapted to additionally set the phase of the anti-signal as a function of a predefined rotational speed, in particular the rotational speed of the electric machine of the drive train and / or the order of the anti-signal. This allows the phase to be very precisely adapted to the current conditions.

[0011] In the context of the invention, the order of the anti-signal represents a multiple of the frequency of a physical variable, for example a multiple of the fundamental oscillation of the phase current of the electric machine. It is conceivable to set the phase for each order that generates a reaction. It is conceivable to set the second-order phase based on the setting of the first-order phase. It is also conceivable to set the third-order phase based on the setting of the second-order phase. Thus, more abstractly expressed, it is conceivable to set the phase of a certain order based on the setting of the phase of a lower order.

[0012] According to another preferred embodiment of the invention, it is proposed that the noise reduction device is adapted to determine the slope of the phase deviation with respect to the rotational speed as a function of the PWM frequency and preferably the order of the anti-signal, in particular by means of a look-up table. This enables the phase to be set quickly and accurately. A look-up table (also abbreviated as LUT) is a conversion table in the context of the invention.

[0013] According to another preferred embodiment of the invention, it is proposed that the noise reduction device is adapted to determine the offset angle as a function of the PWM frequency and preferably the order of the anti-signal, in particular by means of a look-up table. By taking the offset angle into account, the phase of the anti-signal can be set more accurately.

[0014] According to another preferred embodiment of the invention, it is proposed that the noise reduction device is adapted to determine the phase of the anti-signal as

[0015] Δθ PWM =θ off +α PWM ·p·ω m ,

[0016] where Δθ PWMis the corrected phase of the anti-signal, θ off is the offset angle, α PWM is the slope of the phase deviation with respect to the rotational speed, ω m is the mechanical rotational speed of the preferred rotor of the electric machine, and p is preferably the number of pole pairs of the electric machine. By following the rules shown, a very accurate and fast setting of the phase can be achieved. This enables efficient noise reduction. Optionally, it is also possible to store additional mathematical expressions for adapting the phase of the anti-signal according to the rotational speed, PWM frequency, order, and number of pole pairs of the electric machine Δθ PWM (ω_m, f_PWM, μ, p).

[0017] Another subject of the invention for achieving the object stated at the beginning is a drive train having an electric machine, an inverter, and a control unit according to the invention. The electric machine is preferably implemented as three-phase. The inverter preferably has SiC semiconductors and / or GaN semiconductors.

[0018] Another subject of the invention for achieving the object stated at the beginning is a method for operating a drive train having an electric machine, an inverter, and a control unit, the control unit generating PWM pulses for the inverter, wherein the noise reduction device of the control unit generates an anti-signal for active noise reduction, and wherein the noise reduction device sets the corrected phase of the anti-signal according to a predefined PWM frequency. This is corrected by setting the phase of the anti-signal and ensuring the anti-phase of the sound wave and the reverse sound wave.

[0019] According to another preferred embodiment of the invention, it is proposed that the phase of the anti-signal is additionally set according to a predefined rotational speed, in particular the rotational speed of the electric machine and / or the order of the anti-signal. This allows the phase to be very precisely adapted to the current conditions. It is conceivable that the phase of a certain order can be set based on the setting of the phase of a lower order.

[0020] According to another preferred embodiment of the invention, it is proposed that the slope of the phase deviation with respect to the rotational speed is obtained, in particular by means of a look-up table, according to the PWM frequency and preferably the order of the anti-signal. This enables a fast and accurate setting of the phase.

[0021] According to another preferred embodiment of the invention, it is proposed that the offset angle is obtained, in particular by means of a look-up table, according to the PWM frequency and preferably the order of the anti-signal. By taking the offset angle into account, the phase of the anti-signal can be set more accurately.

[0022] According to another preferred embodiment of the invention, it is proposed that the phase of the anti-signal is obtained as

[0023] Δθ PWM = θ off + αPWM ·p·ω m ,

[0024] where Δθ PWM is the corrected phase of the inverse signal, θ off is the offset angle, α PWM is the slope of the phase deviation with respect to the rotational speed, ω m is the rotational speed, and p is the number of pole pairs of the electric machine. By following the rules shown, the phase can be set very accurately and quickly. Thereby, efficient noise reduction is achieved.

[0025] According to another preferred embodiment of the present invention, it is proposed that the control unit is the control unit described according to the present invention.

[0026] Another subject matter of the present invention for achieving the object stated at the beginning is a motor vehicle having a drive train according to the present invention.

[0027] All details, features and advantages previously disclosed in connection with the control unit equally relate to the drive train according to the present invention, the method according to the present invention, and the motor vehicle according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other details, features and advantages of the present invention will result from the drawings and from the following description of preferred embodiments with reference to the drawings. These drawings merely exemplarily show embodiments of the present invention and do not limit the inventive concept.

[0029] Figure 1 The drive train according to an exemplary embodiment of the present invention is schematically shown, which drive train has a control unit according to an exemplary embodiment of the present invention.

[0030] Figure 2 The phase setting in the method according to an exemplary embodiment of the present invention is schematically shown.

[0031] Figure 3 The motor vehicle according to an exemplary embodiment of the present invention is schematically shown. DETAILED DESCRIPTION OF THE INVENTION

[0032] Figure 1 The drive train 10 according to an exemplary embodiment of the present invention is schematically shown, which drive train has a control unit 1 according to an exemplary embodiment of the present invention. The drive train 10 has, for example, a three-phase electric machine 4, which is supplied with phase currents from an inverter 2. For this purpose, the inverter 2 converts the DC voltage provided by an energy storage 5 into an AC voltage, which AC voltages generate phase currents when connected to the terminals of the electric machine 4.

[0033] To this end, the inverter 2 has a plurality of semiconductor switches, preferably SiC semiconductor switches and / or GaN semiconductor switches. The semiconductor switches are controlled by the control unit 1 by means of pulse width modulation (PWM). When the electric machine 4 is operating, typically uncomfortable background noise is generated. To reduce this background noise, the control unit 1 has a noise reduction device 3. The noise reduction device 3 is used to generate an anti-signal for active noise reduction. In the case of active noise reduction, the generated sound waves are reduced or suppressed by generating reverse sound waves. Here, the reverse sound waves are generated by introducing an additional force into the electric machine. Here, the reverse sound waves ideally correspond to the sound waves with a phase shift of 180° in terms of frequency and amplitude.

[0034] It is known from the prior art that an anti-signal is generated for a fixed PWM frequency. It has been shown that when the PWM frequency changes, not only the frequency and amplitude of the anti-signal must be changed. According to the present invention, it is proposed that the noise reduction device 3 sets the phase of the anti-signal according to the PWM frequency (see Figure 2 ). This allows the noise to be suppressed significantly more efficiently by the generated anti-signal.

[0035] In Figure 2 the phase setting Δθ is schematically shown in the method according to an exemplary embodiment of the present invention PWM . The slope α of the phase deviation is looked up in the look-up table LUT by means of the PWM frequency F and the order O of the anti-signal PWM . The offset angle θ is also looked up in another look-up table LUT by means of the PWM frequency F and the order O of the anti-signal off .

[0036] The slope α of the phase deviation PWM is multiplied by the rotational speed ω of the rotor of the electric machine 4 m , which rotational speed increases proportionally to the number of pole pairs p of the electric machine. The result of the multiplication is added to the offset angle θ off , and the phase Δθ of the anti-signal is obtained PWM .

[0037] Figure 3 A motor vehicle 100 according to an exemplary embodiment of the present invention is schematically shown. The motor vehicle 100 has a drive train 10 according to an exemplary embodiment of the present invention.

Claims

1. A control unit (1) for generating PWM pulses for an inverter (2) of a drive train (10), the control unit having a noise reduction device (3) for generating an anti-signal for active noise reduction, characterized in that, The noise reduction device (3) is adapted to set the phase Δθ of the anti-signal according to a predefined PWM frequency F, a predefined rotational speed ω m and the order O of the anti-signal, PWM wherein the phase is set for each order of the anti-signal.

2. The control unit (1) according to claim 1, characterized in that, The noise reduction device (3) is adapted to determine a slope α of a phase deviation with respect to a rotational speed ω by means of a look-up table, as a function of the PWM frequency F and as a function of an order O of the inverse signal m thereof PWM .

3. The control unit (1) according to claim 1 or 2, characterized in that, The noise reduction device (3) is adapted to derive an offset angle θ based on the PWM frequency F and based on the order O of the inverse signal by means of a look-up table off .

4. The control unit (1) according to claim 1 or 2, characterized in that, The noise reduction device (3) is adapted to derive the phase Δθ of the anti-signal PWM For Δθ PWM = θ off + α PWM · p · ω m , where Δθ PWM is the corrected phase of the inverse signal, θ off is the offset angle, α PWM is the slope of the phase deviation with respect to the rotational speed, ω m is the mechanical rotational speed of the rotor of the electric machine, and p is the number of pole pairs of the electric machine (4).

5. The control unit (1) according to claim 1, characterized in that, The pre-given rotational speed is the rotational speed of the electric machine (4) of the drive train (10).

6. A drive train (10) having an electric machine (4), an inverter (2), and a control unit (1) according to one of claims 1 to 5.

7. A method for operating a drive train (10) having an electric machine (4), an inverter (2), and a control unit (1), the control unit generating PWM pulses for the inverter (2), wherein a noise reduction device (3) of the control unit (1) generates an anti-signal for active noise reduction, characterized in that The noise reduction device (3) sets the corrected phase Δθ of the anti-signal according to a pre-given PWM frequency F, a pre-given rotational speed ω m and the order O of the anti-signal, PWM wherein the phase is set for each order of the anti-signal.

8. The method according to claim 7, wherein The phase deviation with respect to the rotational speed ω is obtained by means of a look-up table, based on the PWM frequency F and based on the order O of the inverse signal m for the slope α PWM .

9. The method according to claim 7 or 8, characterized in that The offset angle θ is obtained by means of a look-up table, based on the PWM frequency F and based on the order O of the inverse signal off .

10. The method according to claim 7 or 8, characterized in that Derive the phase Δθ of the anti-signal PWM is Δθ PWM = θ off + α PWM · p · ω m , where Δθ PWM is the corrected phase of the anti-signal, θ off is the offset angle, α PWM is the slope of the phase deviation with respect to the rotational speed, ω m is the rotational speed, and p is the number of pole pairs of the electric machine (4).

11. The method according to claim 7 or 8, characterized in that, The control unit (1) is the control unit (1) according to one of claims 1 to 5.

12. The method according to claim 7, wherein The pre-given rotational speed is the rotational speed of the electric machine (4).

13. A motor vehicle (100) having a drive train (10) according to claim 6.

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