Method for Determining a Rotational Angle Position of a Rotor of a Multiphase Electrical Machine, and Frequency Converter

Abstract

A method for determining a rotational angle position of a rotor of a multiphase electrical machine, includes the steps of: generating phase voltages for the multiphase electrical machine by pulse width modulation in accordance with a drive voltage vector circulating in a stator-fixed coordinate system. During a determination time interval: a) generating a test voltage vector, vectorially adding the test voltage vector and the actual drive voltage vector to form a sum vector, outputting the sum vector, and measuring a resulting change of a current vector formed from phase currents; b) repeating step a) for a changed rotational angle position and/or a changed value of the drive voltage vector and for a changed test voltage vector a number n of times so that a total of n+I different test voltage vectors and sum vectors are generated and n+ I resulting changes of the current vector are measured; and c) estimating the rotational angle position of the rotor in accordance with the total of n+ I measured changes of the current vector.

Claims

1-10. (canceled)

11. A method for determining a rotational angle position of a rotor of a multi-phase electrical machine, the method comprising the steps of: generating phase voltages for the multi-phase electrical machine by way of pulse-width modulation, in accordance with a drive voltage vector circulating in a stator-fixed coordinate system; and executing, during a determination time interval, the steps of: a) generating a test voltage vector; vectorially adding the test voltage vector and an instantaneous drive voltage vector to form a sum vector, and outputting the sum vector and measuring a resulting variation in a current vector formed from the phase currents; b) repeating step a) a number n of times, with a changed rotational angle position and/or a changed value of the drive voltage vector, and with a changed test voltage vector, such that a total of n+1 different test voltage vectors and sum vectors are generated, and n+1 resulting changes of the current vector are measured; and c) estimating the rotational angle position of the rotor in accordance with the total of n+1 measured variations in the current vector.

12. The method according to claim 11, wherein in step a), during one half-pulse or one pulse of pulse-width modulation, the sum vector output is delivered and the resulting variation in the current vector is measured, wherein step a), with a changed rotational angle position and/or a changed value for the drive voltage vector, and with a changed test voltage vector, is repeated a number n of times in the subsequent half-pulses or pulses of pulse-width modulation such that, in n+1 sequential half-pulses or pulses, n+1 different test voltage vectors and sum vectors are generated, and the n+1 resulting variations in the current vector are measured.

13. The method according to claim 11, wherein step a) is repeated three times.

14. The method according to claim 13, wherein a first test voltage vector is antiparallel to a second test voltage vector, a third test voltage vector is antiparallel to a fourth test voltage vector, wherein the first test voltage vector and the second test voltage vector are perpendicular to the third test voltage vector and the fourth test voltage vector.

15. The method according to claim 11, wherein all the test voltage vectors assume an identical value.

16. The method according to claim 11, wherein estimating the rotational angle position is further executed in accordance with the n+1 test voltage vectors and/or in accordance with the drive voltage vector in its different rotational angle positions and/or values.

17. The method according to claim 11, wherein the drive voltage vector, in a subsequent step within the determination time interval, is varied exclusively in a direction of the test voltage vector employed in the preceding step.

18. The method according to claim 11, wherein the value and phase of the current vector are regulated via a current control loop comprising a current controller, wherein the drive voltage vector is employed as a control variable of the current controller, the current vector is formed from the phase currents and a correction value, and the correction value represents a variation in the current vector which is generated by a respective test voltage vector.

19. A frequency converter configured to execute a method according to claim 11.

20. A frequency converter for actuating a multi-phase electrical machine, the frequency converter comprising: an inverter configured to generate phase voltages for the multi-phase electrical machine via pulse-width modulation; a current sensor unit configured to measure phase currents generated by the inverter; a torque regulator that controls a torque generated by the electrical machine, wherein the torque regulator delivers a target current vector as a control variable output; a current controller configured to adjust a value and phase of a current vector obtained from the measured phase currents to the target current vector, wherein the drive voltage vector is employed as a control variable of the current controller; a test voltage vector generation unit, which is configured to generate temporally sequential test voltage vectors; a vector addition unit configured for vectorially adding an instantaneous drive voltage vector and a corresponding test voltage vector to form a sum vector; a PWM unit configured to generate actuation signals for the inverter based on the sum vector, and a rotational angle estimation unit configured to estimate a rotational angle position of the rotor, in accordance with a variation in the current vector which is generated by the test voltage vectors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a highly schematic representation of a frequency converter which is configured for the execution of the method according to an embodiment of the invention;

[0040] FIG. 2 shows exemplary drive voltage vectors and test voltage vectors in a stator-fixed α/β coordinate system;

[0041] FIG. 3 shows exemplary current vectors in the stator fixed α/β coordinate system;

[0042] FIG. 4 shows four exemplary test voltage vectors in the stator-fixed α/β coordinate system, which are employed during a determination time interval for the estimation of a rotational angle position of a rotor of a synchronous machine;

[0043] FIG. 5 shows an exemplary half-pulse of pulse-width modulation; and

[0044] FIG. 6 is a schematic block circuit diagram of a control structure of the frequency converter represented in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 shows a frequency converter 1000, which is configured for the actuation of a three-phase electrical machine 2 in the form of a synchronous motor having a rotor 5, wherein the frequency converter 1000 conventionally comprises three half-bridges B1, B2, B3, each having two semiconductor switching elements S1, S2; S3, S4; S5, S6. The switching elements S1, S2; S3, S4; S5, S6 are actuated by a control unit 3 of the frequency converter 1000.

[0046] With reference to FIG. 1 and FIG. 2, three phase voltages U, V, W for the three phase windings 2a, 2b and 2c of the three-phase electrical machine 2 are generated by means of pulse-width modulation, in accordance with a drive voltage vector AV circulating in a stator-fixed α/β coordinate system KS, which initiate a rotation of the rotor 5.

[0047] For the estimation of the rotational angle position α (see FIG. 1) of the rotor 5, the following steps are executed during a determination time interval DI (see FIG. 5).

[0048] Firstly, a test voltage vector TV1 is generated, and the test voltage vector TV1 and an instantaneous drive voltage vector AV1 are vectorially added thereafter to form a sum vector SV1. The sum vector SV1 is delivered as an output by the appropriate positional setting of the half-bridges B1, B2, B3, and by means of appropriate PWM actuation. Finally, a resulting variation in a current vector I1 formed from the phase currents iu, iv, iw is measured - see FIG. 3.

[0049] These steps are repeated n = 3 times with a changed rotational angle position and a changed value of the drive voltage vector AV, and with a changed test voltage vector TV, such that a total of four different test voltage vectors TV1 to TVn+1 or TV4 and sum vectors SV1 to SVn+1 to SV4 are generated, and n+1 or four resulting variations in the current vector I1 to In+1 or I4 are measured.

[0050] Finally, the rotational angle position α of the rotor 5 is estimated in accordance with the total of four measured variations in the current vector I1 to I4, the four test voltage vectors TV1 to TV4, and in accordance with the drive voltage vector AV1 to AV4, in its different rotational angle positions and/or values.

[0051] With reference to FIG. 4, the first test voltage vector TV1 is antiparallel to the second test vector TV2, the third test voltage vector TV3 is antiparallel to the fourth test voltage TV4, wherein the first test voltage vector TV1 and the second test voltage vector TV2 are perpendicular to the third test vector TV3 and the fourth test voltage vector TV4. All the test voltage vectors TV1 to TV4 assume an identical value, and are comprised exclusively of components in the +-α-direction or the +-β-direction.

[0052] With reference to FIG. 5, the determination time interval DI extends over a total of four half-pulses TK1 to TK4 or half-cycles of pulse-width modulation, and consequently assumes a duration which corresponds to two pulse-width modulation cycles.

[0053] FIG. 6 is a schematic representation of a block circuit diagram of a control structure of the frequency converter 1000.

[0054] The frequency converter 1000 comprises an inverter 1001, which can be configured as represented in FIG. 1, and is configured to generate phase voltages U, V, W for the three-phase electrical machine 2 by means of pulse-width modulation.

[0055] The frequency converter 1000 further comprises a current sensor unit 1002, which is configured for the measurement of phase currents iu, iv, iw produced by means of the inverter. In the present case, only the currents iu and iw are determined by means of appropriate current sensors, wherein the current iv is determined computationally.

[0056] The frequency converter 1000 further comprises a torque regulator 1004 for controlling a torque which is generated by means of the electrical machine 2, wherein the torque regulator 1004 delivers a target current vector IS as a control variable output.

[0057] The frequency converter 1000 further comprises a current controller 1005, which is configured to adjust the value and phase of the current vector I or Ik formed from the measured phase currents iu, iv, iw to the target current vector IS, wherein the drive voltage vector AV is employed as a control variable of the current controller 1005.

[0058] The frequency converter 1000 further comprises a test voltage vector generation unit 1006, which is configured to generate the temporally sequential test voltage vectors TV1 to TV4.

[0059] The frequency converter 1000 further comprises a vector addition unit 1003, which is configured for the vectorial addition of the instantaneous drive voltage vector AV and a corresponding test voltage vector TV to form a sum vector SV.

[0060] The frequency converter 1000 further comprises a PWM unit 1008, which is configured to generate actuation signals for the inverter 1001 on the basis of the sum vector SV.

[0061] The frequency converter 1000 further comprises a rotational angle estimation unit 1007, which is configured to estimate a rotational angle position α of the rotor 5, in accordance with a variation in the current vector I which is generated by the test voltage vectors TV.

[0062] The value and phase of the current vector I are regulated by means of the current control loop, having the current controller 1005. A corrected current vector Ik of the current control loop, delivered as an output from the rotational angle estimation unit 1007, is formed in the rotational angle estimation unit 1007 from the phase currents iu, iv, iw and a correction value KW, wherein the correction value KW represents a variation in the current vector I associated with a respective test voltage vector TV1 to TV4. This prevents any corruption of the output of the test voltage vectors TV1 by the current controller 1005.