MOTOR DRIVING APPARATUS

• US 20200136538A1
• Filed: 07/05/2018
• Published: 04/30/2020
• Est. Priority Date: 07/11/2017
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: JUNG, Hansu, KIM, Kwang Sik, LEE, Chungill
• Granted Patent: US 11,165,373 B2
• Time in Patent Office: Days
• CPC Class Codes: H02P 21/18 Estimation of position or speed
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop
• CPC Class Codes: H02P 21/24 Vector control not involving the use of rotor position or rotor speed sensors
• CPC Class Codes: H02P 2203/01 Motor rotor position determination based on the detected or calculated phase inductance, e.g. for a Switched Reluctance Motor
• CPC Class Codes: H02P 6/18 without separate position detecting elements

Abstract

The present disclosure relates to a motor driving apparatus and, more specifically, to a motor driving apparatus which allows a maximum torque operation by correcting an angle error occurring during quick acceleration of a motor in a sensorless system. The motor driving apparatus comprises: an inverter for driving a motor, using an alternating current voltage; and a control unit for outputting a PWM signal for controlling an operation of a switching element included in the inverter. Here, the control unit determines an inductance parameter used to calculate a speed command value for determining a duty ratio of a PWM signal, and determines whether the motor is being accelerated, on the basis of a current change measured from the inverter. When the motor is being accelerated, the control unit enables a maximum torque operation by reducing an angle error of a rotor through a correction of reducing a previously-determined inductance parameter.

Claims

1. A motor driving apparatus, comprising:

an inverter that drives a motor; and

a control unit that outputs a PWM signal for controlling operations of a switching element included in the inverter,

wherein the control unit determines an inductance parameter used to calculate a speed command value for determining a duty ratio of the PWM signal, and

the control unit corrects a size of the determined inductance parameter, on the basis of whether the motor is being accelerated.

2. The motor driving apparatus of claim 1, wherein the control unit determines whether the motor is being accelerated, on the basis of a change in electric currents measured by the inverter, and

wherein, when the motor is being accelerated, the control unit reduces a size of the inductance parameter.

3. The motor driving apparatus of claim 2, wherein the control unit reduces a size of the inductance parameter using a predetermined correction ratio, and

the correction ratio is determined on the basis of a change in speeds of the motor.

4. The motor driving apparatus of claim 3, wherein the control unit corrects a size of the inductance parameter in inverse proportion to the change in speeds.

5. The motor driving apparatus of claim 1, wherein the inductance parameter is determined using a regression equation or a table prestored in the control unit, on the basis of sizes of electric currents measured by the inverter, and

wherein, when the motor is being accelerated, a size of the determined inductance parameter is corrected on the basis of a change in speeds of the motor.

6. The motor driving apparatus of claim 1, wherein the control unit comprises:

a current command generator that generates a current command value using the speed command value calculated on the basis of a command speed and on the basis of a present speed of the motor,

a voltage command generator that generates a voltage command value on the basis of the current command value and on the basis of electric currents measured by the inverter,

a PWM generator that outputs the PWM signal on the basis of the voltage command value and on the basis of an electrical angle position of the motor, and

a sensorless controller that calculates the present speed and the electrical angle position of the motor on the basis of a voltage reconfigured based on the PWM signal and on the basis of electric currents measured by the inverter.

7. The motor driving apparatus of claim 6, wherein the sensorless controller determines the inductance parameter corresponding to sizes of electric currents measured by the inverter using a prestored regression equation or table,

the sensorless controller determines whether the motor is being accelerated, on the basis of a change in electric currents measured by the inverter, and

when the motor is being accelerated, the sensorless controller reduces a size of the inductance parameter.

8. The motor driving apparatus of claim 7, wherein the sensorless controller corrects a size of the inductance parameter in inverse proportion to a gradient of changes in speeds of the motor.

9. The motor driving apparatus of claim 8, wherein, when the gradient of changes in speeds becomes steep, the sensorless controller reduces a size of the inductance parameter, and

when the gradient of changes in speeds becomes gentle, the sensorless controller increases a size of the inductance parameter.

10. The motor driving apparatus of claim 6, wherein the sensorless controller calculates an active flux vector using a q-axis current vector extracted from electric currents measured by the inverter and using the inductance parameter, and

the sensorless controller calculates the present speed and the electrical angle position of the motor on the basis of an angle between the active flux vector and a d-axis.

11. The motor driving apparatus of claim 10, wherein the control unit reduces the inductance parameter such that the active flux vector has a lead angle with respect to the d-axis, and

when the active flux vector has a lead angle with respect to the d-axis, the control increases the current command value by increasing the speed command value.

12. The motor driving apparatus of claim 1, wherein the control unit corrects a size of the inductance parameter such that the motor is driven at a speed greater than 80 krpm.

13. A motor driving apparatus, comprising:

a motor that includes a stator around which three-phase coils are wound and that includes a rotor which is placed in the stator and which is rotated by a magnetic field generated in the three-phase coils;

an inverter that includes three-phase switching elements which performs switch-on and switch-off operations to supply three-phase AC voltages to the three-phase coils and to cut off the three-phase AC voltages; and

a control unit that outputs a PWM signal which controls operations of the three-phase switching elements.

wherein the control unit determines whether the motor is being accelerated, on the basis of a change in electric currents measured by the inverter,

wherein, when the motor is being accelerated, the control unit reduces a size of an inductance parameter used to determine a duty ratio of the PWM signal.

14. The motor driving apparatus of claim 13, wherein the control unit determines an inductance parameter for calculating a speed command value on the basis of sizes of electric currents measured by the inverter, and

wherein, when the motor is being accelerated, the control unit makes a correction by reducing a size of the determined inductance parameter.

15. The motor driving apparatus of claim 13, wherein the inductance parameter is determined using sizes of electric currents measured by the inverter and using a regression equation or a table prestored in the control unit, and

wherein, when the motor is being accelerated, a size of the determined inductance parameter is corrected on the basis of a gradient of changes in speeds of the motor.

16. The motor driving apparatus of claim 15, wherein, when the gradient of changes in speeds becomes steep, the control unit reduces a size of the inductance parameter, and

when the gradient of changes in speeds becomes gentle, the control unit increases a size of the inductance parameter.

17. The motor driving apparatus of claim 13, wherein the control unit comprises:

a current command generator that generates a current command value using a speed command value calculated on the basis of a command speed and on the basis of a present speed of the motor,

a voltage command generator that generates a voltage command value on the basis of the current command value and on the basis of electric currents measured by the inverter,

a PWM generator that outputs the PWM signal on the basis of the voltage command value and on the basis of an electrical angle position of the motor, and

a sensorless controller that calculates the present speed and the electrical angle position of the motor on the basis of a voltage reconfigured based on the PWM signal and on the basis of electric currents measured by the inverter.

18. The motor driving apparatus of claim 17, wherein the sensorless controller corrects a size of the inductance parameter in inverse proportion to a change in speeds of the motor.

19. The motor driving apparatus of claim 17, wherein the sensorless controller calculates an active flux vector using a q-axis current vector extracted from electric currents measured by the inverter and using the inductance parameter, and

the sensorless controller calculates the present speed and the electrical angle position of the motor on the basis of an angle between the active flux vector and a d-axis.

20. The motor driving apparatus of claim 13, wherein the control unit corrects a size of the inductance parameter such that the motor is driven at a speed greater than 80 krpm.