Inverter control device

Patent metadata

Field	Value
Publication number	US-11456691-B2
Application number	US-201917293622-A
Country	US
Kind code	B2
Filing date	Aug 7, 2019
Priority date	Nov 21, 2018
Publication date	Sep 27, 2022
Grant date	Sep 27, 2022

Abstract

The present disclosure provides an inverter control device which estimates back electromotive force of an induction motor, and which uses a torque current and a flux current so as to calculate a slip frequency and compensate for same, thereby enabling the motor to operate at a constant speed. To this end, the present invention may comprise: a command voltage generating unit for outputting, to an inverter, a three phase PWM voltage with respect to a command frequency on the basis of a voltage/frequency operation; and a slip frequency determining unit for determining a slip frequency on the basis of a phase current and a phase voltage of a motor driven by the inverter.

First claim

What is claimed is:

1. An inverter control device comprising:
a command voltage generating unit configured to receive a command frequency and output 3-phases PWM voltage to an inverter, based on voltage/frequency operation; and
a slip frequency determining unit configured to determine a slip frequency based on phase current and phase voltage of a motor driven by the inverter,
wherein the slip frequency determining unit includes:
a coordinate converting unit configured to:
convert the phase current and the phase voltage of the motor to dq-axis phase currents and phase voltages of a stationary coordinate system;

a disturbance measurement unit configured to:
estimate a back electromotive force of the motor from the dq-axis currents and voltages; and
estimate a phase angle of the rotor magnetic flux from the back electromotive force of the motor;

a current estimating unit configured to apply the phase angle of the rotor magnetic flux to the dq-axis phase currents to convert the dq-axis phase currents to a torque-based current and a magnetic flux-based current of the rotation coordinate system; and
a frequency estimating unit configured to output an estimated slip frequency based on the torque-based current, the magnetic flux-based current and a rotor time constant.

2. The inverter control device of claim 1 , wherein the coordinate converting unit includes:
dq-axis phase current converting unit configured to convert 3-phases stator currents into dq-axis phase currents of the stationary coordinate system; and
dq-axis phase voltage converting unit configured to convert 3-phases stator voltages into dq-axis phase voltages of the stationary coordinate system.

3. The inverter control device of claim 1 , wherein the disturbance measurement unit includes:
a back electromotive force estimating unit configured to apply a stator resistance and a leakage inductance to the dq-axis phase currents and voltages and pass the dq-axis phase currents and voltages through a low-pass filter to estimate a back electromotive force of the motor; and
a phase angle estimating unit configured to estimate the phase angle of the rotor magnetic flux from the back electromotive force of the motor.

4. The inverter control device of claim 3 , wherein the back electromotive force estimating unit is configured to estimate the back electromotive force of the motor based on a following [Equation]:

E
dqrs_est

=

K
p

σ
⁢

L
s

⁢
s

+

K
i

σ
⁢

L
s

s
2

+

K
p

o
⁢

L
s

⁢
s

+

K
i

σ
⁢

L
s

⁢

(

V

d
⁢
q
⁢
s
⁢
s

-

R
s

⁢

i

d
⁢
q
⁢
s
⁢
s

-

s
⁢
σ
⁢

L
s

⁢

i

d
⁢
q
⁢
s
⁢
s

)

[
Equation
]

where E dqrs

Assignees

• Ls Electric Co Ltd

Inventors

• Choi Seung-Cheol
• Lee Hak-Jun

Classifications

• H02M7/53875 Primary

  with analogue control of three-phase output · CPC title

• H02P21/14 Primary

  Estimation or adaptation of machine parameters, e.g. flux, current or voltage · CPC title

• H02M7/5395

  by pulse-width modulation · CPC title

• H02P21/0003

  Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control · CPC title

• H02P27/08 Primary

  with pulse width modulation · CPC title