INVERTER VECTOR DRIVING SYSTEM AND METHOD FOR ESTIMATING CAPACITANCE USING THE SAME

• US 20160282392A1
• Filed: 03/25/2016
• Published: 09/29/2016
• Est. Priority Date: 03/25/2015
• Status: Active Grant

• Current Assignee: Research Cooperation Foundation Of Yeungnam University
• Original Assignee: Research Cooperation Foundation Of Yeungnam University
• Inventors: LEE, Dong-Choon, NGUYEN, Thanh Hai, JEUNG, Yoon-Cheul
• Granted Patent: US 9,722,523 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 7/5387 in a bridge configuration
• CPC Class Codes: H02P 21/36 Arrangements for braking or slowing; Four quadrant control

Abstract

The present invention relates to an inverter vector driving system and a method for estimating capacitance using the same. The present invention provides a method for estimating capacitance in an inverter vector driving system including a capacitor to which a rectified DC voltage of a three-phase power supply is charged, and a PWM inverter configured to transform the DC voltage into a three-phase AC voltage to be applied to a motor of an induction motor, including: operating the motor of the IM in a regeneration mode; generating a d-axis voltage command and a q-axis voltage command for the motor; adjusting a pulse of the PWM inverter by using the d-axis voltage command and the q-axis voltage command; and estimating capacitance of the capacitor by using a DC-link voltage and a DC-link current that are generated at the capacitor due to the inclusion of the AC component.

Claims

1. A method for estimating capacitance in an inverter vector driving system including a capacitor to which a rectified DC voltage of a three-phase power supply is charged and a PWM inverter configured to transform the DC voltage into a three-phase AC voltage to be applied to an induction motor (IM), comprising:

operating the motor in a regeneration mode;

generating a d-axis voltage command using a d-axis current command of a d-q coordinate system for the motor and a d-axis DC current obtained from the motor, and generating a q-axis voltage command using a q-axis current command, a q-axis DC current obtained from the motor, a q-axis current command including a predetermined AC component, and a q-axis AC current obtained from the motor;

adjusting a pulse of the PWM inverter by using the d-axis voltage command and the q-axis voltage command; and

estimating capacitance of the capacitor by using a DC-link voltage and a DC-link current that are generated at the capacitor due to the inclusion of the AC component.

2. The method of claim 1, wherein the q-axis AC current and the q-axis DC current are obtained by allowing the q-axis current of the motor on the d-q coordinate system obtained during an operation of the motor to respectively pass through a band pass filter (BPF) and a band stop filter (BSF).

3. The method of claim 1 or claim 2, wherein

the generating of the d-axis voltage command and the q-axis voltage command includes:

generating the d-axis voltage command by performing proportional integral control of a value obtained by subtracting the d-axis DC current from the d-axis current command; and

generating the q-axis voltage command by summing a result of performing proportional integral control of a value obtained by subtracting the q-axis DC current from the q-axis current command, and a result of performing proportional resonant control of a value obtained by subtracting the q-axis AC current from a q-axis current command including the AC component.

4. The method of claim 1, wherein

the DC-link current (i_de,cal) is calculated by the following Equation:

5. The method of claim 4, wherein

the estimating of capacitance of the capacitor includes

estimating capacitance of the capacitor by using the recursive least square algorithm (RLS algorithm) such that an error cost function has a minimum value:

e₂(n)=└

BPF[i_dc(n)]−

Ĉ

(n)BPF[v′

_dc(n)]┘

²

wherein, e²(n) is an error cost function, BPF[·

] is an output value passed through the band pass filter (BPF), i_dc is the DC-link current, v_dc is the DC-link voltage, and Ĉ

(n) is estimated capacitance of the capacitor.

6. The method of claim 5, wherein

the estimated capacitance of the capacitor is updated by the following equation:

13. The method of claim 2, wherein

the generating of the d-axis voltage command and the q-axis voltage command includes:

generating the d-axis voltage command by performing proportional integral control of a value obtained by subtracting the d-axis DC current from the d-axis current command; and

generating the q-axis voltage command by summing a result of performing proportional integral control of a value obtained by subtracting the q-axis DC current from the q-axis current command, and a result of performing proportional resonant control of a value obtained by subtracting the q-axis AC current from a q-axis current command including the AC component.

7. An inverter vector driving system for estimating capacitance comprising:

a capacitor to which a rectified DC voltage of a three-phase power supply is charged;

a PWM inverter configured to transform the DC voltage into a three-phase AC voltage to be applied to a motor of an IM;

a calculating unit configured, while the motor is operated in a regeneration mode, to generate a d-axis voltage command using a d-axis current command of a d-q coordinate system for the motor and a d-axis DC current obtained from the motor, and to generate a q-axis voltage command using a q-axis current command, a q-axis DC current obtained from the motor, a q-axis current command including a predetermined AC component, and a q-axis AC current obtained from the motor;

a pulse adjusting unit configured to adjust a pulse of the PWM inverter by using the d-axis voltage command and the q-axis voltage command; and

an estimating unit configured to estimate capacitance of the capacitor by using a DC-link voltage and a DC-link current which are generated at the capacitor by the inclusion of the AC component.

8. The system of claim 7, wherein

the q-axis AC current and the q-axis DC current are obtained by

allowing the q-axis current of the motor on the d-q coordinate system obtained during an operation of the motor to respectively pass through a band pass filter (BPF) and a band stop filter (BSF).

9. The system of claim 7, wherein

the calculating unit is configured to

generate the d-axis voltage command by performing proportional integral control of a value obtained by subtracting the d-axis DC current from the d-axis current command, and

to generate the q-axis voltage command by summing a result of performing proportional integral control of a value obtained by subtracting the q-axis DC current from the q-axis current command and a result of performing proportional resonant control of a value obtained by subtracting the q-axis AC current from a q-axis current command including the AC component.

10. The system of claim 7, wherein the DC-link current (i_dc,cal) is calculated by the following equation:

11. The system of claim 10, wherein

the estimating unit is configured to estimate

capacitance of the capacitor by using the recursive least square algorithm (RLS algorithm) such that an error cost function has a minimum value:

e²(n)=└

BPF[i_dc(n)]−

Ĉ

(n)BPF[v′

_dc(n]┘

²

wherein, e²(n) is an error cost function, BPF[·

] is an output value passed through the band pass filter (BPF), i_dc is the DC-link current, v_dc is the DC-link voltage, and is estimated capacitance of the capacitor.

12. The system of claim 11, wherein

the estimated capacitance of the capacitor is updated by the following equation:

14. The system of claim 8, wherein

the calculating unit is configured to

generate the d-axis voltage command by performing proportional integral control of a value obtained by subtracting the d-axis DC current from the d-axis current command, and

to generate the q-axis voltage command by summing a result of performing proportional integral control of a value obtained by subtracting the q-axis DC current from the q-axis current command and a result of performing proportional resonant control of a value obtained by subtracting the q-axis AC current from a q-axis current command including the AC component.