Multi-phase motor/generator system with harmonic injection

1. A method comprising:

configuring a system with a motor and an inverter, wherein the motor has a plurality of symmetrical windings coupled to the inverter;

configuring the inverter to inject a plurality of high-order synchronous harmonic currents into the windings of the motor, wherein the high-order synchronous harmonic currents are configured to generate a rotating magnetic field in the motor at the same speed and in the same direction as a magnetic field generated by fundamental currents in the plurality of windings of the motor; and

in response to an increased phase number, a reduced pole number and a corresponding saturation region change from a tooth area to a yoke area, adjusting a phase-shift of one of the high-order synchronous harmonic currents to reduce a magnetic saturation of the yoke area in the motor and increase a torque of the motor in an operation mode.

2. The method of claim 1 , wherein:

the plurality of high-order harmonic currents are generated by a plurality of high-order harmonics comprising a third-order harmonic.

3. The method of claim 1 , wherein:

the motor is an induction motor.

4. The method of claim 3 , wherein the plurality of windings are configured such that a number of poles of the motor can be dynamically adjustable by adjusting currents flowing through the plurality of windings; and

a controller configured to determine an injection ratio of a high-order harmonic current to a fundamental frequency current.

5. The method of claim 1 , further comprising:

establishing a desirable waveform of current in the plurality of windings for achieving a desirable performance of the system.

6. The method of claim 1 , further comprising:

determining an injection ratio of a high-order harmonic current to a fundamental current, wherein the injection ratio for a magnetizing component is different from the injection ratio for a torque component at a same harmonic frequency.

7. The method of claim 6 , further comprising:

determining the injection ratio based on a power loss of the system or a power loss of a component of the system.

8. The method of claim 6 , wherein:

the motor is a permanent magnet motor.

9. The method of claim 1 , wherein:

the motor is a reluctance motor.

10. A system comprising:

a motor having a plurality of symmetric windings, a rotor and a stator magnetically coupled to the rotor;

a plurality of power inverters connected to respective windings, wherein the plurality of power inverters are configured to control currents of the plurality of windings; and

a controller configured to determine an injection ratio of a high-order synchronous harmonic component to a fundamental component for currents of the plurality of windings, and wherein the high-order synchronous harmonic component is configured to generate a rotating magnetic field at the same speed and in the same direction as a magnetic field generated by the fundamental component, and wherein in response to an increased phase number, a reduced pole number and a corresponding saturation region change from a tooth area to a yoke area, a phase-shift of one of the high-order synchronous harmonic currents is adjusted to reduce a magnetic saturation of the yoke area in the motor and increase a torque of the motor in an operation mode.

11. The system of claim 10 , wherein the controller comprises:

a first transform unit configured to convert detected current signals-of the plurality of windings into current variables in a synchronous d-q frame;

a first field-oriented control unit configured to generate reference magnetizing and torque current signals for the fundamental component; and

a second field-oriented control unit configured to generate reference magnetizing and torque current signals in the d-q frame for the high-order harmonic component.

12. The system of claim 11 , wherein:

an injection ratio for the high-order harmonic torque current reference to the fundamental torque current reference is different from an injection ratio for the high-order harmonic magnetizing current reference to the fundamental magnetizing current reference.

13. The system of claim 11 , wherein:

the high-order synchronous harmonics currents are configured to selectively alleviate magnetic saturation of tooth areas or yoke areas of the stator or the rotor of the motor in different operation modes.

14. The system of claim 10 , wherein:

the motor is an induction motor.

15. The system of claim 14 , wherein:

the number of poles and the number of phases of the motor are dynamically reconfigurable.

16. A method comprising:

configuring a motor drive system with a motor and an inverter, wherein:

the motor has a stator, a rotor and a plurality of symmetric windings arranged into a plurality of winding groups; and

the inverter has a plurality of power converter groups, and wherein each power converter group is configured to control currents of a winding group;

injecting a plurality of high-order synchronous harmonic currents into the plurality of windings of the motor;

configuring the system such that the high-order synchronous harmonics currents generate a rotating magnetic field at the same speed and in the same direction as a magnetic field generated by fundamental currents of the plurality of windings; and

in response to an increased phase number, a reduced pole number and a corresponding saturation region change from a tooth area to a yoke area, adjusting a phase-shift of one of the high-order synchronous harmonic currents to reduce a magnetic saturation of the yoke area in the motor and enhance a torque of the motor in an operation mode.

17. The method of claim 16 , further comprising:

dynamically adjusting the number of poles of the motor drive system by adjusting currents flowing through a plurality of windings of the motor drive system.

18. The method of claim 16 , further comprising:

converting the synchronous harmonic into a magnetizing current variable and a torque current variable in a d-q frame; and

controlling a first injection ratio of the magnetizing current variable to a fundamental magnetizing current and a second injection ratio of the torque current variable to the fundamental torque current independently.

19. The method of claim 18 , further comprising:

determining the first injection ratio and the second injection ratio based on a power loss of the motor drive system or a power loss of a component of the motor drive system.

20. The method of claim 16 , further comprising:

configuring the high-order synchronous harmonics currents to selectively alleviate magnetic saturation of tooth areas or yoke areas of the stator or the rotor-of the motor in different operation modes.