Direct torque control of AC electric machines

Patent metadata

Field	Value
Publication number	US-9831812-B2
Application number	US-201615055289-A
Country	US
Kind code	B2
Filing date	Feb 26, 2016
Priority date	Feb 27, 2015
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

This disclosure features an apparatus including a motor controller to generate control signals to control an electric motor. The motor controller includes a first saturation controller to generate a first saturation controller output based on feedback signals associated with the electric motor. The motor controller further includes a duty ratio modulator coupled to the first saturation controller. The duty ratio modulator is configured to determine activation times for a set of voltage vectors based on the first saturation controller output. The motor controller is configured to generate, at each switching cycle, a control signal based on the set of voltage vectors and the activation times for the set of voltage vectors, and provide the control signal for controlling the electric motor.

First claim

What is claimed is:

1. An apparatus comprising:
a motor controller to generate control signals to control an electric motor, the motor controller comprising
a first saturation controller to generate a first saturation controller output based on feedback signals associated with the electric motor, and
a duty ratio modulator coupled to the first saturation controller, the duty ratio modulator being configured to determine activation times for a set of voltage vectors based on the first saturation controller output,

wherein the motor controller is configured to generate, at each switching cycle, a control signal based on the set of voltage vectors and the activation times for the set of voltage vectors, and provide the control signal for controlling the electric motor.

2. The apparatus of claim 1 , further comprising the electric motor.

3. The apparatus of claim 2 , wherein the electric motor is an alternating current motor.

4. The apparatus of claim 1 , wherein the first saturation controller is configured to generate the first saturation controller output based on a difference between an estimated torque of the electric motor and a reference torque.

5. The apparatus of claim 1 in which the duty ratio modulator is configured to determine the activation times for the set of voltage vectors based on a hysteresis controller output and the first saturation controller output.

6. The apparatus of claim 1 in which the feedback signals are representative of a voltage and a current applied to the electric motor.

7. The apparatus of claim 1 , wherein the motor controller comprises a switching table containing sets of voltage vectors, the switching table being configured to select the set of voltage vectors based on the feedback signals.

8. The apparatus of claim 7 , wherein the motor controller further comprises a hysteresis controller configured to generate a hysteresis controller output based on the feedback signals, and the switching table is configured to select the set of voltage vectors based on the hysteresis controller output.

9. The apparatus of claim 7 , further comprising an estimator to estimate a torque of the electric motor and a stator flux of the electric motor based on the feedback signals, wherein the switching table is configured to select the set of voltage vectors based on a position of the stator flux within a sector of a stationary reference frame.

10. The apparatus of claim 1 , wherein the set of vectors comprises at least two active vectors.

11. The apparatus of claim 1 , wherein the set of vectors comprises at least one passive vector.

12. The apparatus of claim 1 , wherein the set of vectors comprises at least two passive vectors.

13. The apparatus of claim 12 , wherein the duty ratio modulator is configured to select a first activation time of a first passive vector and a second activation time of a second passive vector based on a predetermined weighting factor.

14. The apparatus of claim 1 , wherein:
the motor controller comprises a second saturation controller to generate a second saturation controller output based on the feedback signals, and
the duty ratio modulator is further connected to the second saturation controller, the duty ratio modulator being configured to determine the activation times for the set of voltage vectors based on the first saturation controller output and the second saturation controller output.

15. The apparatus of claim 14 , wherein the second saturation controller is configured to generate the second saturation controller output based on a difference between an estimated stator flux of the electric motor and a reference stator flux.

16. The apparatus of claim 1 , further comprising an inverter coupled to the electric motor, wherein the motor controller is configured to apply the control signal to the inverter to place the inverter in one of a plurality of inverter states, each inverter state corresponding to one voltage vector among the set of voltage vectors, and the inverter being in each inverter state for a corresponding activation time.

17. The apparatus of claim 1 , wherein the first saturation controller is configured such that available values of the first saturation controller output include a low state, a high state, and a range of states between the low state and the high state.

18. The apparatus of claim 17 , wherein the first saturation controller is configured such that a value of the first saturation controller output corresponds to
the low state if a value of the feedback signals is less than a first predefined threshold,
the high state if the value of the feedback signals is greater than a second predefined threshold, and
a state in the range of states if the value of the feedback signals is between the first predefined threshold and the second predefined threshold.

19. The apparatus of claim 1 , wherein:
the duty ratio modulator is configured to, for each switching cycle, determine a first percentage of a switching period of a switching cycle to activate a first vector of the set of vectors and a second percentage of the switching period to activate a second vector of the set of vectors, the first and second percentages being proportional to a value of the first saturation controller output, and
the motor controller is configured to generate the control signal to activate the first vector for the first percentage of the switching period and to activate the second vector for the second percentage of the switching period.

20. A method of controlling an electric motor system, the method comprising:
determining activation times for a set of voltage vectors based on a first saturation controller output; and
generating, at each switching cycle, a control signal to control an electric motor based on the set of voltage vectors and the activation times for the set of voltage vectors.

21. The method of claim 20 , further comprising generating the first saturation controller output based on a difference between an estimated torque of the electric motor and a reference torque.

22. The method of claim 20 , wherein generating the control signal to control the electric motor comprises causing an alternating current to be delivered to the electric motor.

23. The method of claim 20 , further comprising:
receiving feedback signals indicative of a voltage and a current applied to the electric motor, and
generating the first saturation controller output based on the feedback signals.

24. The method of claim 23 , further comprising selecting the set of voltage vectors from predefined sets of voltage vectors based on the feedback signals.

25. The method of claim 24 , further comprising estimating a torque and a stator flux based on the feedback signals, and
wherein selecting the set of voltage vectors comprises selecting the set of voltage vectors based on a position of the stator flux within a sector of a stationary reference frame.

26. The method of claim 23 , further comprising generating a hysteresis controller output based on the feedback signals,
wherein selecting the set of voltage vectors comprises selecting the set of voltage vectors based on the hysteresis controller output.

27. The method of claim 20 , wherein the set of vectors comprises at least two active vectors.

28. The method of claim 20 , wherein the set of vectors comprises at least one passive vector.

2

Assignees

• Nutech Ventures

Inventors

• Qiao Wei
• Zhang Zhe
• Qu Liyan

Classifications

• H02P21/30 Primary

  Direct torque control [DTC] or field acceleration method [FAM] · CPC title

• H02P21/20

  Estimation of torque · CPC title

• H02P21/141

  Flux estimation · CPC title