Method and apparatus for control of an AC electric motor with field weakening
View Patent ↗A method and apparatus for control of an alternating current electric motor with field weakening, including setting a required operating point for a motor field voltage component as a function of a difference between actual and required motor field current components, and setting a required operating point for a motor torque voltage component as a function of a difference between actual and required motor torque current components. The method also includes setting a field weakening constituent for the required operating point for the motor field voltage component as a function of a difference between a required operating point and an available value of the motor torque voltage component and as a function of a difference between actual and required motor torque current components.
1. A method for control of an alternating current electric motor with field weakening, comprising:
setting a required operating point for a motor field voltage component as a function of a difference between actual and required motor field current components;
setting a required operating point for a motor torque voltage component as a function of a difference between actual and required motor torque current components;
setting a field weakening constituent for said required operating point for said motor field voltage component as a function of a difference between a required operating point and an available value of said motor torque voltage component and as a function of a difference between actual and required motor torque current components.
2. A method for control of an electric motor as claimed in claim 1 , wherein setting said required operating point for a motor torque voltage component and setting said required motor torque current component include responding to values available after setting said required operating point for said field voltage component and setting a required motor field current component.
3. A method for control of an electric motor as claimed in claim 1 , wherein setting said required operating points for said motor field voltage component and for said motor torque voltage component includes proportional-integral control in response to differences between their respective actual and required current components.
4. A method for control of an electric motor as claimed in claim 1 , wherein setting said field weakening constituent of said required operating point for said motor field voltage component includes proportional-integral control in response to said difference between a required operating point and an available value of said motor torque voltage components and to said difference between actual and required motor torque current components.
5. A method for control of an electric motor as claimed in claim 1 , wherein setting said required operating points for a motor field voltage component and for a motor torque voltage component includes setting limits for said motor field and torque voltage components as a function of an available supply voltage.
6. A method for control of an electric motor as claimed in claim 1 , wherein setting said required motor field and torque current components includes setting limits for said motor field and torque current components.
7. A method for control of an electric motor as claimed in claim 1 , wherein said motor field components are D-axis components of motor currents and voltages expressed in rotating coordinates and said motor torque components are Q-axis components of motor currents and voltages expressed in said rotating coordinates.
8. An apparatus for control of an electric motor with field weakening, comprising:
a field control module for setting a required operating point for a motor field voltage component as a function of a difference between actual and required motor field current components;
a torque control module for setting a required operating point for a motor torque voltage component as a function of a difference between actual and required motor torque current components;
wherein said field control module is arranged to receive inputs from a field weakening module for setting a field weakening constituent of said required operating point for said motor field voltage component as a function of a difference between a required operating point and an available value of said motor torque voltage component and as a function of a difference between actual and required motor torque current components.
9. An apparatus for control of an electric motor as claimed in claim 8 , wherein said torque control module is arranged to set said required operating point for a motor torque voltage component and said required motor torque current component in response to values available after said field control module sets said required operating point for said field voltage component and sets a required motor field current component.
10. An apparatus for control of an electric motor as claimed in claim 8 , wherein said field control module and said torque control module include proportional-integral control elements for setting said required operating points for said motor field voltage component and for said motor torque voltage component in response to differences between their respective actual and required current components.
11. An apparatus for control of an electric motor as claimed in claim 8 , wherein said field weakening module includes a proportional-integral control element for setting said field weakening constituent of said required operating point for said motor field voltage component in response to said difference between a required operating point and an available value of said motor torque voltage components and to said difference between actual and required motor torque current components.
12. An apparatus for control of an electric motor as claimed in claim 8 , wherein said field control module and said torque control module are arranged to set limits for said motor field and torque voltage components as a function of an available supply voltage in setting said required operating points for a motor field voltage component and for a motor torque voltage component.
13. An apparatus for control of an electric motor as claimed in claim 8 , wherein said field control module and said torque control module are arranged to set limits for said motor field and torque current components in setting said required motor field and torque current components.
14. An electric motor arrangement comprising an electric motor and apparatus for control of the electric motor as claimed in claim 8 .
15. A method for control of an electric motor as claimed in claim 2 , wherein setting said required operating points for said motor field voltage component and for said motor torque voltage component includes proportional-integral control in response to differences between their respective actual and required current components.
16. A method for control of an electric motor as claimed in claim 2 , wherein setting said field weakening constituent of said required operating point for said motor field voltage component includes proportional-integral control in response to said difference between a required operating point and an available value of said motor torque voltage components and to said difference between actual and required motor torque current components.
17. A method for control of an electric motor as claimed in claim 2 , wherein setting said required operating points for a motor field voltage component and for a motor torque voltage component includes setting limits for said motor field and torque voltage components as a function of an available supply voltage.
18. A method for control of an electric motor as claimed in claim 2 , wherein setting said required motor field and torque current components includes setting limits for said motor field and torque current components.
19. A method for control of an electric motor as claimed in claim 3 , wherein setting said required motor field and torque current components includes setting limits for said motor field and torque current components.
20. A method for control of an alternating current electric motor with field weakening, comprising:
setting a required operating point for a motor field voltage component as a function of a difference between actual and required motor field current components;
setting a required operating point for a motor torque voltage component as a function of a difference between actual and required motor torque current components;
setting a field weakening constituent for said required operating point for said motor field voltage component as a function of a difference between a required operating point and an available value of said motor torque voltage component, wherein said difference between said required operating point and said available value of said motor torque voltage component is scaled with respect to a torque current component error, and as a function of a difference between actual and required motor torque current components.