Method and device for determining the position angle of a rotor in an electric synchronous machine

1. A method for determining the position angle of a rotor ( 2 ) of an electric synchronous machine ( 1 ), the method comprising:

generating (S 10 ) in each case at least one electric voltage pulse with predetermined electrical angles in a stator-fixed coordinate system, referred to as a stator ( 3 ) of the electric synchronous machine ( 1 ), when the rotor ( 2 ) of the synchronous machine ( 1 ) is stationary, the at least one electrical voltage pulse being generated in such a way that the rotor is not made to rotate;

measuring (S 20 ) in each case at least one respective electrical current value arising from the generated electrical voltage pulses;

storing (S 30 ) a current signal profile of the measured current values corresponding to each of the predetermined electrical angles;

generating (S 40 ) a mean-value-free current signal profile by shifting the stored current signal profile or the measured current values;

calculating (S 50 ) an integral function ( 83 ) of the mean-value-free signal current profile; and

determining (S 60 ) the position angle of the rotor ( 2 ) on the basis of the calculated integral function ( 83 ),

wherein the determination (S 60 ) of the position angle of the rotor ( 2 ) includes determining a mean value ( 84 ) of the calculated integral function ( 83 ) and determining a first angle value ( 85 ) at which the calculated integral function ( 83 ) intersects the determined mean value ( 84 ) of the calculated integral function ( 83 ), and

wherein the determination (S 60 ) of the position angle of the rotor ( 2 ) is carried out on the basis of the determined first angle value ( 85 ).

2. The method as claimed in claim 1 ,

wherein a respective electrical angle which is increased by 180° is also predetermined for each predetermined angle; and

wherein the current signal profile of the measured current values is stored only in accordance with angles in one half of 360°, wherein the value for each predetermined electrical angle in the one half of 360° is acquired both from at least one current value which is measured for this predetermined electrical angle and from at least one current value which is measured for the predetermined electrical angle which is shifted by 180°.

3. The method as claimed in claim 1 , wherein that angle value at which the calculated integral function ( 83 ) intersects the determined mean value ( 84 ) of the calculated integral function ( 83 ) during a rise in the calculated integral function ( 83 ) from low values to relatively high values is determined as the first angle value ( 85 ).

4. The method as claimed in claim 3 ,

wherein in addition a second angle value is determined at which the calculated integral function ( 83 ) intersects the determined mean value ( 84 ) of the calculated integral function ( 83 ) during a drop in the calculated integral function ( 83 ) from relatively high values to relatively low values, and

wherein the determination (S 60 ) of the position angle of the rotor ( 2 ) additionally takes place on the basis of the determined second angle value ( 86 ).

5. The method as claimed in claim 1 , wherein a sum, an average, or both of the measured current values at the first angle value ( 85 ) is compared with a sum, an average, or both of the measured current values at a third angle value which is equal to the determined first angle value ( 85 ) plus 180°, and wherein of the first angle value ( 85 ) and the second angle value that angle value for which the sum, the average, or both of the measured current values is larger is determined as the position angle of the rotor ( 2 ).

6. The method as claimed in claim 1 , wherein the determination (S 60 ) of the position angle of the rotor ( 2 ) also includes: generating a first electrical saturation pulse electrically with the determined first angle value ( 85 ); measuring a first electrical current value which arises from the first electrical saturation pulse; generating a second electrical saturation pulse electrically with a third angle value which is the same as the determined first angle value ( 85 ) plus 180°; measuring a second electrical current value which arises from the second electrical saturation pulse; determining the first angle value as a position angle of the rotor ( 2 ) if the first electrical current value is higher than the second electrical current value, and determining the third angle value as a position angle of the rotor ( 2 ) if the second electrical current value is higher than the first electrical current value.

7. The method as claimed in claim 1 ,

wherein with each of the predetermined electrical angles a multiplicity of voltage pulses is generated and the electrical current values which arise in each case therefrom are measured; and wherein the current signal profile is stored on the basis of all the measured current values.

8. The method as claimed in claim 1 ,

wherein the current values of the stored signal profile are each provided by the mean value or the sum of all the electrical current values acquired for a respective predetermined electrical angle.

9. The method as claimed in claim 1 ,

wherein after the generation of each voltage pulse a pulse is generated in the opposing direction,

and

wherein a predetermined time period between the generation of each voltage pulse and the pulse in the opposing direction is between 1 microsecond and 500 microseconds.

10. A device ( 10 ) for determining the position angle of a rotor ( 2 ) of an electric synchronous machine ( 1 ), the device comprising:

a voltage generating device ( 12 ) which is configured to generate (S 10 ) in each case at least one electrical voltage pulse at predetermined electrical angles in a stator-fixed coordinate system, referred to as a stator ( 3 ) of the electric synchronous machine ( 1 ), when the rotor ( 2 ) of the synchronous machine ( 1 ) is stationary, the at least one electrical voltage pulse being generated in such a way that the rotor is not made to rotate;

a measuring device ( 14 ) which is configured to measure (S 20 ) in each case at least one respective electrical current value which arises from the electrical voltage pulses generated by the voltage generating device ( 12 ); and

a computing device ( 16 ) which is configured:

to store a current signal profile of the measured current values corresponding to each of the predetermined electrical angles;

to generate a mean-value-free current signal profile by shifting the current signal profile and/or the measured current values;

to calculate an integral function ( 83 ) of the mean-value-free current signal profile; and

to determine the position angle of the rotor ( 2 ) on the basis of the calculated integral function ( 83 )

wherein the determination of the position angle of the rotor ( 2 ) includes determining a mean value ( 84 ) of the calculated integral function ( 83 ) and determining a first angle value ( 85 ) at which the calculated integral function ( 83 ) intersects the determined mean value ( 84 ) of the calculated integral function ( 83 ), and wherein the determination of the position angle of the rotor ( 2 ) is carried out on the basis of the determined first angle value ( 85 ).

11. The device ( 10 ) as claimed in claim 10 ,

wherein the voltage generating device ( 12 ) is configured in such a way that a respective electrical angle which is increased by 180° is also predetermined for each predetermined angle; and

wherein the computing device ( 16 ) is configured to store the current signal profile of the current values in accordance with only angles in one half of 360°, wherein the value for each predetermined electrical angle in the one half of 360° is acquired both from at least one current value which is measured for this predetermined electrical angle and from at least one current value which is measured for the predetermined electrical angle which is shifted by 180°.