Acceleration method for V/F controlled induction motor in flux-weakening region

Patent metadata

Field	Value
Publication number	US-10340776-B2
Application number	US-201515506785-A
Country	US
Kind code	B2
Filing date	Aug 25, 2015
Priority date	Aug 29, 2014
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

The present invention provides an acceleration method for V/f controlled induction motor in flux-weakening region, which comprises: acquiring no-load magnetizing current Im of the induction motor at current stator frequency; selecting a smaller one of 0.5·Im(1/σ+1) and (Im2+σ)/(Im+σIm) as magnetizing current set point, in which σ is an estimated total leakage inductance coefficient; getting an error signal by subtracting the magnetizing current of the induction motor from the magnetizing current set point; determining the stator frequency for the next control period according to the error signal which is provided as a controlling variable of negative feedback. The acceleration method of the present invention can provide the maximum output torque in flux-weakening region and has a larger tolerance for the error of the estimated leakage inductance.

First claim

The invention claimed is:

1. An acceleration method for a V/f controlled induction motor in a flux-weakening region comprising:
acquiring a no-load magnetizing current I m of the V/f controlled induction motor at a current stator frequency;
selecting a smaller one of 0.5·I m (1/σ+1) and (I m 2 +σ)/(I m +σI m ) as a magnetizing current set point, in which σ is an estimated total leakage inductance coefficient;
acquiring an error signal by subtracting a magnetizing current of the V/f controlled induction motor from the magnetizing current set point, wherein the error signal is provided as a controlling variable of negative feedback; and
determining a stator frequency for a next control period according to the error signal.

2. The acceleration method of claim 1 further comprising:
determining an acceleration value of the stator frequency as a controlled variable according to the error signal; and
determining a stator frequency for the next control period according to the acceleration value of the stator frequency.

3. The acceleration method of claim 2 further comprising setting the stator frequency for the next control period as a predetermined stator frequency when the determined stator frequency for the next control period is greater than a predetermined stator frequency.

4. The acceleration method of claim 2 further comprising:
acquiring the acceleration value of the stator frequency with a proportional integral controller; and
determining the acceleration value of the stator frequency to be equal to the error signal multiplied by K p +K i /s, where K p is a proportional adjustment coefficient, K i is an integral adjustment coefficient, and s represents the frequency domain.

5. The acceleration method of claim 2 further comprising:
acquiring the acceleration value of the stator frequency with a proportional integral controller; and
determining the acceleration value of the stator frequency to be equal to the error signal multiplied by (K p +K i /s)/ω e (n), where K p is a proportional adjustment coefficient, K i is an integral adjustment coefficient, s represents a frequency domain, and ω e (n) is a per unit value of the current stator frequency.

6. The acceleration method of claim 1 further comprising acquiring the no-load magnetizing current by dividing a rated no-load magnetizing current of the V/f controlled induction motor by a per unit value of the current stator frequency.

7. The acceleration method of claim 1 further comprising estimating the estimated total leakage inductance coefficient according to an off-line parameter identification method of the V/f controlled induction motor.

8. An acceleration system for a V/f controlled induction motor in a flux-weakening region comprising:
a no-load magnetizing current acquiring device for acquiring a no-load magnetizing current I m of the V/f controlled induction motor at a current stator frequency;
a magnetizing current setting device for selecting a smaller one of 0.5·I m (1/σ+1) and (I m 2 +σ)/(I m +σI m ) as a magnetizing current set point, in which σ is an estimated total leakage inductance coefficient;
an error signal calculating device for acquiring an error signal by subtracting a magnetizing current of the V/f controlled induction motor from the magnetizing current set point, wherein the error signal is provided as a controlling variable of negative feedback; and
a stator frequency determining device for determining a stator frequency for a next control period according to the error signal.

9. The acceleration system of claim 8 wherein the stator frequency determining device comprises:
a negative feedback controller for acquiring an acceleration value of the stator frequency as a controlled variable according to the error signal; and
a stator frequency calculating device for determining the stator frequency for the next control period according to the acceleration value of the stator frequency.

10. The acceleration system of claim 9 wherein the stator frequency determining device further comprises a stator frequency limiting device for setting the stator frequency for the next control period as a predetermined stator frequency when the determined stator frequency for the next control period is greater than a predetermined stator frequency.

11. The acceleration system of claim 9 wherein the negative feedback controller is a proportional integral controller; and
wherein the stator frequency acceleration value is equal to the error signal multiplied by K p +K i /s, where K p is a proportional adjustment coefficient, K i is an integral adjustment coefficient, and s represents the frequency domain.

12. The acceleration system of claim 9 wherein the negative feedback controller is a proportional integral controller; and
wherein the stator frequency acceleration value is equal to the error signal multiplied by (K p +K i /s)/ω e (n), where K p is a proportional adjustment coefficient, K i is an integral adjustment coefficient, s represents a frequency domain, and ω e (n) is a per unit value of the current stator frequency.

13. The acceleration system of claim 8 wherein the no-load magnetizing current acquiring device is configured to acquire the no-load magnetizing current by dividing a rated no-load magnetizing current of the V/f controlled induction motor by the per unit value of the current stator frequency.

14. The acceleration system of claim 8 wherein the magnetizing current setting device is further configured to estimate the estimated total leakage inductance coefficient according to an off-line parameter identification method of the V/f controlled induction motor.

15. A V/f controlling system comprising the acceleration system for a V/f controlled induction motor of claim 8 .

Assignees

• Eaton Corp
• Univ Zhejiang
• Eaton Intelligent Power Ltd

Inventors

• Lee Kevin
• Wang Kai
• Yao Wenxi

Classifications

• H02P1/30

  by progressive increase of frequency of supply to primary circuit of motor · CPC title

• H02P1/28

  by progressive increase of voltage applied to primary circuit of motor · CPC title

• H02P27/047 Primary

  V/F converter, wherein the voltage is controlled proportionally with the frequency · CPC title

• H02K17/02 Primary

  Asynchronous induction motors · CPC title

• H02P23/0031

  implementing a off line learning phase to determine and store useful data for on-line control · CPC title