METHOD AND APPARATUS FOR OPERATING AN ELECTRICAL DRIVE SYSTEM

• US 20130193896A1
• Filed: 01/08/2013
• Published: 08/01/2013
• Est. Priority Date: 01/12/2012
• Status: Active Grant

• Current Assignee: MBDA UK Ltd. (MBDA SAS)
• Original Assignee: MBDA UK Ltd. (MBDA SAS)
• Inventors: Lynn, David Mark, Kirkland, Leonard James
• Granted Patent: US 9,391,556 B2
• Time in Patent Office: Days
• US Class Current: 318/490
• CPC Class Codes: B60L 15/025 using field orientation; Vector control; Direct Torque Control [DTC]
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 3/1586 switched with a phase shift, i.e. interleaved
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H02P 21/04 specially adapted for very low speeds
• CPC Class Codes: H02P 21/36 Arrangements for braking or slowing; Four quadrant control
• CPC Class Codes: H02P 31/00 Arrangements for regulating or controlling electric motors not provided for in groups H02P1/00 - H02P5/00, H02P7/00 or H02P21/00 - H02P29/00
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An electrical drive system includes an electric motor having an armature, which is mounted on a stator, and a rotor, wherein aligning stator flux with rotor flux enables current to flow in the armature without inducing torque on the rotor shaft. The disclosed operation may be used, for example, in testing the electrical drive system. The electric drive system can carry full rated current yet produce little or no torque, thereby increasing the current that can be tested during electrical drive test procedures without producing undesired forces or motion. The method may be used, for example, in heating the electric motor, for example for de-icing.

Claims

1. A method of operating an electrical drive system that includes an electric motor having a stator, a rotor and an armature, and which can be represented as having two armature phases, the method comprising:

i) driving the motor in accordance with a non-zero current demand profile to produce a direct axis current and/or a quadrature axis current in the armature;

ii) aligning flux produced by the stator with flux produced by the rotor;

iii) monitoring the a position of the rotor; and

iv) controlling the direct axis current and/or the quadrature axis current to avoid or minimise rotation of the rotor.

2. A method as claimed in claim 1, in which the current demand profile comprises:

driving the motor at full-rated or near full-rated current.

3. A method as claimed in claim 1, comprising:

aligning stator and rotor fluxes by controlling a current flowing in the armature.

4. A method as claimed in claim 1, comprising:

aligning stator and rotor fluxes by controlling a voltage across the armature.

5. A method as claimed in claim 4, in which the motor has 3 or more phases and the method comprises:

monitoring at least 2 related phases of a current in the armature.

6. A method as claimed in claim 5, comprising:

calculating a direct-axis armature current and/or a quadrature-axis armature current from the at least 2 monitored phases and the rotor position.

7. A method as claimed in claim 1, comprising:

controlling the direct-axis current according to a non-zero current demand profile.

8. A method as claimed in claim 7, wherein the non-zero current demand profile comprises:

full-rated or near full-rated current demand.

9. A method as claimed in claim 1, comprising:

controlling the quadrature-axis current to be non-zero.

10. A method as claimed in claim 1, wherein said monitoring comprises:

sensing any rotation of the rotor, and said controlling comprises;

compensating for rotor rotation by adjusting the direct-axis current and/or the quadrature-axis current.

11. A method according to claim 10, wherein said controlling comprises:

compensating for rotor rotation by adjusting the quadrature-axis current.

12. A method as claimed in claim 1, comprising:

calculating a 3-phase voltage demand that generates the a demanded direct-axis current and/or quadrature-axis current.

13. A method as claimed in claim 1, comprising:

i. monitoring the rotor position and current in the armature in at least two phases;

ii. transforming the monitored current into direct-axis and quadrature-axis current components, relative to a frame of reference aligned with the monitored rotor position;

iii. comparing the direct-axis current and quadrature-axis current components against target values for those components;

iv. calculating direct-axis and quadrature-axis voltages across the armature needed to produce the current component target values;

v. transforming the calculated direct-axis and quadrature-axis voltages back into an original frame of reference;

vi. applying the transformed calculated voltages to the armature;

vii. optionally, pausing; and

viii. repeating from the monitoring of (i).

14. A method as claimed in claim 1, wherein the motor comprises:

a dc brushless motor.

15. An electrical drive system, comprising:

an electric motor having a stator and a rotor;

a control system configured to align flux produced by the stator with flux produced by the rotor;

a rotor monitor for monitoring a position of the rotor;

a direct-axis current controller;

a quadrature-axis current controller; and

a feedback loop for controlling the direct axis current and/or the quadrature axis current to avoid or minimise rotation of the rotor.

16. A system as claimed in claim 15 wherein the control system, when in use, comprises:

a non-zero current demand profile to produce a direct axis current and/or a quadrature axis current in the armature.

17. A system as claimed in claim 16 wherein the non-zero current demand profile is configured, when in use to produce a direct axis current comprising full-rated or near full-rated current demand.

18. A system as claimed in claim 15 wherein the rotor monitor is configured to sense any rotation of the rotor, and the feedback loop is connected to receive an output of the rotor monitor and to produce a quadrature axis current to compensate that rotation.

19. A system as claimed in claim 15, in which the control system is also configured to align, in an alternative mode of operation, the stator and rotor fluxes such that torque is produced on the rotor.

20. A system as claimed in claim 15 wherein the motor comprises:

a dc brushless motor.

21. A system as claimed in claim 15, in which the electric motor is configured to produce mechanical motion to actuate a mechanism.

22. A system as claimed in claim 21, in which the mechanism is a latching or unlatching mechanism.