METHOD FOR DETERMINING A ROTOR FREQUENCY AND/OR A ROTOR ANGLE OF A ROTOR OF A RELUCTANCE MACHINE, CONTROL DEVICE, AND DRIVE ASSEMBLY

Abstract

A method for determining a rotor frequency and/or a rotor angle of a rotor of a reluctance machine, in particular without an amortisseur, is disclosed. The reluctance machine has a stator with a stator winding and the rotor has a magnetically anisotropic rotor core. The method includes applying a temporal sequence of voltage pulses to the stator winding, determining a sequential pulse response of a current flowing in the stator winding, the current being generated as a result of the voltage pulses and a flux being generated from the voltage pulses as a result of the magnetically anisotropic rotor core, and determining the rotor frequency and/or the rotor angle based on the measured sequential pulse response of the electric current by using an evaluating device.

Claims

1.-8. (canceled)

9. A method, comprising: applying a temporal sequence of voltage pulses to a stator winding of a stator of a reluctance machine via a frequency converter by alternately outputting a voltage value of a fixed amount and a fixed direction and a pulse block in a sequential repetition; and determining a rotor frequency and/or a rotor angle of a rotor of the reluctance machine by measuring a sequential pulse response of an electric current by using an evaluating device, said electric current having a negative-phase component representing a part of the electric current changing as a function of the rotor angle and a positive-phase component representing a part of the electric current not undergoing a change as a function of the rotor angle, wherein the sequential pulse response of the electric current, which flows in the stator winding is generated as a result of the voltage pulses, and a flux is thereby sequentially generated from the voltage pulses as a result of the rotor having a magnetically anisotropic rotor core.

10. The method of claim 9, wherein the rotor frequency and/or the rotor angle is determined based on a geometry of the rotor core.

11. The method of claim 9, further comprising preparing a phase and/or a frequency of a temporal course of the electric current using a phase control loop of a control device.

12. The method of claim 11, wherein the control device has at least one meter and/or one detector used for determining maximum values for the measured electric current and/or a time interval between at least two adjacent maxima of the temporal course of the electric current.

13. The method of claim 9, wherein the rotor frequency and/or the rotor angle is determined when the rotor is stationary or when the rotor is rotating relative to the stator.

14. The method of claim 9, wherein a converter is connected to the reluctance machine based on the determined rotor frequency and/or the rotor angle.

15. A control device for a converter of a reluctance machine, comprising: at least one meter and/or one detector for determining a rotor frequency and/or a rotor angle of a rotor of the reluctance machine, said at least one meter and/or one detector determining maximum values for a measured electric current and/or a time interval between at least two adjacent maxima of a temporal course of the electric current, said control device, by operating the at least one meter and/or the one detector is configured to: apply a temporal sequence of voltage pulses to a stator winding of a stator of the reluctance machine via a frequency converter by alternately outputting a voltage value of a fixed amount and a fixed direction and a pulse block in a sequential repetition; and determine the rotor frequency and/or the rotor angle of the rotor of the reluctance machine by measuring a sequential pulse response of the electric current via an evaluating device, said electric current having a negative-phase component representing a part of the electric current changing as a function of the rotor angle and a positive-phase component representing a part of the electric current not undergoing a change as a function of the rotor angle, wherein the sequential pulse response of the electric current, which flows in the stator winding is generated as a result of the voltage pulses, and a flux is thereby sequentially generated from the voltage pulses as a result of the rotor having a magnetically anisotropic rotor core.

16. A drive assembly, comprising: a reluctance machine; a converter electrically connected to the reluctance machine; and a control device for controlling the converter, said control device including at least one meter and/or one detector for determining a rotor frequency and/or a rotor angle of a rotor of the reluctance machine, said at least one meter and/or one detector determining maximum values for a measured electric current and/or a time interval between at least two adjacent maxima of a temporal course of the electric current, said control device, by operating the at least one meter and/or the one detector is configured to: apply a temporal sequence of voltage pulses to a stator winding of a stator of the reluctance machine via a frequency converter by alternately outputting a voltage value of a fixed amount and a fixed direction and a pulse block in a sequential repetition; and determine the rotor frequency and/or the rotor angle of the rotor of the reluctance machine by measuring a sequential pulse response of the electric current via an evaluating device, said electric current having a negative-phase component representing a part of the electric current changing as a function of the rotor angle and a positive-phase component representing a part of the electric current not undergoing a change as a function of the rotor angle, wherein the sequential pulse response of the electric current, which flows in the stator winding is generated as a result of the voltage pulses, and a flux is thereby sequentially generated from the voltage pulses as a result of the rotor having a magnetically anisotropic rotor core.

Description

[0023] The invention is now explained in greater detail on the basis of a preferred exemplary embodiment and with reference to the appended drawings, in which:

[0024] FIG. 1 shows a rotor coordinate system of a reluctance machine, in which a current vector and a flux vector are illustrated with their trajectories;

[0025] FIG. 2 shows a stator coordinate system of the reluctance machine, in which the current vector and the flux vector are illustrated with their trajectories;

[0026] FIG. 3 shows the stator coordinate system, in which measured values for the electric current are recorded;

[0027] FIG. 4 shows the stator coordinate system and the rotor coordinate system of the reluctance machine;

[0028] FIG. 5 shows an evaluating device of a drive assembly;

[0029] FIG. 6 shows the drive assembly with the reluctance machine, a converter, a measuring device and the control device; and

[0030] FIG. 7 shows the drive assembly according to FIG. 6 in a further embodiment variant.

[0031] It is intended here to determine a rotor frequency f and/or a rotor angle φ of a reluctance machine 2. The reluctance machine 2 is designed in particular as a synchronous reluctance machine without amortisseur. The reluctance machine 2 comprises a stator (not shown) having corresponding stator windings 10. The reluctance machine 2 also comprises a rotor (not shown) having a rotor core that is so designed as to be magnetically anisotropic. The rotor core can be made of a laminated core and have corresponding flux blocking elements, i.e. air-filled regions or voids, whereby the magnetically anisotropic embodiment is produced. On the basis of the rotor frequency f and/or the rotor angle φ that has been determined, in particular a converter 6 can be connected to the rotating reluctance machine 2 at the correct rotational speed and phase.

[0032] FIG. 1 shows a rotor coordinate system having the axis d and the axis q. In the rotor coordinate system, physical variables of the reluctance machine 2 are represented as vectors in the complex plane. The axis d shows the real part of the rotor coordinate system and in the direction of the high permeance. The axis q shows the imaginary part of the rotor coordinate system and in the direction of the low permeance. In the present exemplary embodiment, the rotor rotates at the frequency ω. In the rotor coordinate system, a magnetic flux φ is drawn as a flux vector. The flux vector is so impressed here as to be fixed relative to the stator. With ideal linear observation, the flux φ or the flux vector in the rotor coordinate system appears on a circular trajectory rotating at the frequency −ω.

[0033] As a result of the flux φ, an electric current I is produced in the stator winding 10. The rotor of the reluctance machine 2 or the rotor core thereof has a magnetic anisotropy, i.e. the rotor has a direction-dependent permeance. By virtue of this property, an impressed flux φ which advances on a circular trajectory relative to the rotor results in a corresponding path of a current vector which describes the electric current I. The path of the current I or the current vector is derived from the geometric embodiment and/or the magnetic anisotropy of the rotor core. In the present exemplary embodiment, an elliptical path of the current vector is produced with regard to the rotor system.

[0034] FIG. 2 shows the courses as per FIG. 1 from the perspective of the flux vector, i.e. in the stator coordinate system. The stator coordinate system has the axis α and the axis β. The axis α shows the real part and the axis β shows the imaginary part of the stator coordinate system. The flux vector or the flux φ appears stationary in this case. The current vector describing the electric current I can be broken down into a positive-phase component I.sub.0 and a negative-phase component I′. The positive-phase component I.sub.0 is in phase with the flux φ. The negative-phase component I′ rotates in the direction of the running rotor at double the frequency 2ω. The temporal change of the electric current I is produced by the temporal change of the negative-phase component I′.

[0035] FIG. 3 shows a sequence of measured values 5 for the electric current I in the stator coordinate system. In the reluctance machine 2, the flux φ is generated e.g. as a high-frequency sequential pulse train {φ.sub.k} with constant direction. The notation of the pair of braces is used to describe a sequence here. For this purpose, a voltage value of fixed amount and fixed direction and a pulse block {U.sub.k, Z.sub.k} are output alternately in each case in sequential repetition by means of a frequency converter. The flux vector is created when voltage U.sub.k is applied, and decays again in the next cycle when the pulse block Z.sub.k is applied. In this way, the required pulse train for the flux {φ.sub.k} is quasi shot into the machine in sequential repetition.

[0036] A diagram of the resulting stator current pulse train {I.sub.k} is shown on the basis of the measured values 5. The measured values 5 form a circular trajectory in the stator coordinate system, with offset displacement I.sub.0 relative to the origin O. The offset displacement is caused by the positive-phase component I.sub.0 of the electrical current I.sub.k. The associated circular trajectory is caused by the negative-phase component I′ and contains the information for the rotor angle φ. If the positive-phase component I.sub.0 or offset displacement is known, the rotor angle φ and/or the rotor frequency f can therefore be determined from the measured values 5 of the current {I.sub.k} after subtracting I.sub.0.

[0037] The offset displacement can either be calculated in advance if the motor parameters are known, or determined in advance by arithmetic averaging of the measured values 5 if the motor parameters are not known. Alternatively, it can be determined in advance by generating the average from the minimum and the maximum of the measured values 5.

[0038] FIG. 4 shows a space vector illustration of the reluctance machine 2. The space vector illustration comprises the stator coordinate system and the rotor coordinate system rotating relative to the stator coordinate system. It can be seen here that the sequence of voltage pulses {U.sub.k, Z.sub.k} results in the generation of a flux φ or a flux vector which is fixed relative to the stator and has a fixed direction relative to the axis α. The voltage pulses {U.sub.k, Z.sub.k} result in a sequence of current vectors {I.sub.k} whose values I.sub.k, I.sub.k+1, I.sub.k+2 lie on a circle with offset displacement. The sequence of the negative-phase component {I′.sub.k}={I.sub.k}−I.sub.0, which is produced after subtracting the offset I.sub.0 from {I.sub.k} and is marked in the diagram by the connecting vectors from I.sub.0 to the values I.sub.k, contains respectively the information for the doubled rotor angle φ and the information for the doubled rotor frequency f as shown.

[0039] FIG. 5 shows a schematic illustration of an evaluating device 3 for determining the rotor frequency f and/or a rotor angle φ. The evaluating device 3 is supplied with the temporal response sequence of the electric current {I.sub.k} which is captured using a current sensor 7 for example. Furthermore, the offset displacement I.sub.0 is subtracted from the electric current {I.sub.k}. Therefore the sequence of the negative-phase component {I′.sub.k} of the electric current {I.sub.k} is supplied to a phase control loop 4. The phase control loop 4 is clocked at the frequency of the voltage signal {U.sub.k} in particular. The angle argument of the temporal course of the negative-phase component {I′.sub.k} can be determined by means of a device 11. An offset angle is also added to the angle argument. Furthermore, the device 12 is used to reduce the current angle and the current frequency by the factor 2. The rotor frequency f and the rotor angle φ can thus be determined by the phase control loop 4.

[0040] FIG. 6 shows a drive assembly 1 in a first embodiment variant. The drive assembly 1 comprises the reluctance machine 2. The drive assembly 1 also comprises the control device 3. The drive assembly 1 further comprises the converter 6, which is designed as a frequency converter in particular. The converter 6 is electrically connected to the stator winding 11. In the present exemplary embodiment, the stator winding 11 has three phases. The voltage pulses U.sub.k are now impressed into the stator winding 11. These give rise to the electric current I in the stator winding 10, which is captured by the current sensor 7.

[0041] FIG. 7 shows the drive assembly 1 in a further embodiment variant. Instead of the phase control loop 4, provision is made for a corresponding meter 8 which can determine the time between the zero crossings of the temporal course of the electric current I and can therefore determine the rotor frequency f. Provision is also made for a detector 9, in particular a max/min detector, which can determine the rotor angle φ or the phase on the basis of the maximum values of the electric current I.

[0042] Using the drive assemblies 1 according to FIG. 6 and FIG. 7, the rotor frequency f and the rotor angle φ can be reliably determined. Assuming a frequency of the voltage U.sub.k of 1 kHz and an identification duration of 50 ms, for example, a rotor frequency f from 0 Hz to approximately ±100 Hz can be determined. At a higher frequency, the performance characteristics can be increased.

[0043] By virtue of the low signal energy, the method for determining the rotor frequency f and/or the rotor angle φ is quasi noiseless and torque-free. Furthermore, the converter 6 can be connected to the rotating reluctance machine 2 at the correct rotational speed and phase.