Electricity: motive power systems – Induction motor systems
Reexamination Certificate
2001-02-26
2003-08-26
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Induction motor systems
C318S767000, C318S800000, C318S801000, C318S805000, C318S807000, C318S808000, C318S812000
Reexamination Certificate
active
06611124
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control apparatus for an AC motor, and more particularly, it relates to a technology for estimating a constant of the AC motor.
2. Description of the Related Art
Heretofore, as a control apparatus for an AC motor, to which a control method is applied, there has been available a control apparatus having such a constitution as shown in FIG.
3
. In
FIG. 3
, a reference numeral
1
denotes an AC power source;
2
a converter;
3
a smoothing capacitor;
4
an inverter;
5
a current detector;
6
an induction motor;
11
a speed control unit;
12
a
a voltage operation unit;
13
a voltage conversion unit;
14
a q-axis current control unit;
15
a d-axis current control unit;
16
a correction voltage operation unit;
17
a d-axis secondary magnetic flux command unit;
18
a
a frequency operation unit;
19
an integrator;
20
a current conversion unit; and
21
a
a speed estimation unit.
An AC voltage outputted from the AC power source
1
is rectified by the converter
2
, and smoothed by the smoothing capacitor
3
to be converted into a DC voltage. The DC voltage thus obtained by the conversion is converted into an AC voltage by the inverter
4
in accordance with a U-phase voltage command Vu*, a V-phase voltage command Vv* and a W-phase voltage command Vw*, which are all outputs from the voltage conversion unit
13
. Then, the induction motor
6
is driven. A U-phase current Iu and a W-phase current Iw flowing through the induction motor
6
are detected by the current detector
5
. The detected currents Iu and Iw are subjected to rotational coordinate transformation at the current conversion unit
20
based on a phase &thgr;, which is an output from the integrator
19
, and then converted into a d-shaft current Id and a q-axis current Iq as the components of a dq rotational coordinate system.
On the other hand, the speed control unit
11
controls a q-axis current command Iq* in such a way as to cause an estimated speed &ohgr;r{circumflex over ( )} outputted from the speed estimation unit
21
a
to coincide with a speed command &ohgr;r* provided from an external unit. At the q-axis current control unit
14
, a q-axis current control quantity &Dgr;Vqo is outputted based on an expression (1) using a q-axis current command Iq* and a q-axis current Iq outputted from the speed control unit
11
. In the expression (1) below, Kpcq and Kicq represent control gains, and s represents a differential operator.
Δ
Vq0
=
(
Kpcq
+
Kicq
s
)
·
(
Iq
*
-
0
q
)
(
1
)
At the d-axis current control unit
15
, a d-axis current control quantity &Dgr;Vd0 is outputted based on an expression (2) using a d-axis current command Id* and a d-axis current Id provided from the external unit. In the expression (2) below, Kpcd and Kicd represent control gains.
Δ
Vd0
=
(
Kpcd
+
Kicd
s
)
·
(
Id
*
-
Id
)
(
2
)
At the correction voltage operation unit
16
, a d-axis voltage correction quantity &Dgr;Vd and a q-axis voltage correction quantity &Dgr;Vq are computed based on an expression (3) using the d-axis current control quantity &Dgr;Vd0 and the q-axis current control quantity &Dgr;Vq0. In the expression (3) below, Kd and Kq represent control gains.
(
Δ
Vd
Δ
Vq
)
=
(
Kd
0
Kq
1
)
·
(
Δ
Vd0
Δ
Vq0
)
(
3
)
At the voltage operation unit
12
a,
d-axis and q-axis voltage commands Vd* and Vq* as voltage commands in the dq rotational coordinate system are computed based on an expression (4) using the d-axis current command Id*, the q-axis current command Iq*, a d-axis secondary magnetic flux command &phgr;d* outputted from the d-axis secondary magnetic flux command unit
17
, a frequency command value &ohgr;1* outputted from the frequency operation unit
18
, the d-axis voltage correction quantity &Dgr;Vd and the q-axis voltage correction quantity &Dgr;Vq. In the expression (4), R1* represents a primary resistance set value; L&sgr;* a leakage inductance set value converted to the primary side; and Km an inductance ratio calculated from mutual inductance M* and secondary inductance L2* based on an expression (5).
(
Vd
*
Vq
*
)
=
(
R1
*
ω
1
*
·
L
σ
*
ω
1
*
·
L
σ
*
R1
*
)
·
(
Id
*
Iq
*
)
+
(
0
ω
1
*
·
Km
*
·
φ
d
*
)
+
(
Δ
Vd
Δ
Vq
)
(
4
)
Km
*
=
M
*
L2
*
(
5
)
The d-axis and q-axis voltage commands Vd* and Vq* computed at the voltage operation unit
12
a
are subjected to transformation from a q-axis rotational coordinate axis to a fixed coordinate axis by the voltage conversion unit
13
based on a phase &thgr; outputted from the integrator
19
, and converted into a U-phase voltage command Vu*, a V-phase voltage command Vv*, and a W-phase voltage command Vw*. Then, voltage control is carried out.
A d-axis secondary magnetic flux command &phgr;d* is computed from the d-axis current command Id* at the d-axis secondary magnetic flux command unit
17
based on an expression (6).
&phgr;
d*=M*·Id*
(6)
At the frequency control unit
18
, a frequency command value &ohgr;1* is computed based on an expression (7) using the q-axis current command Id*, the d-axis secondary magnetic flux command &phgr;d*, and a speed estimated value &ohgr;r{circumflex over ( )} outputted from the speed estimation unit
21
a.
In the expression (7) below, R2* represents a secondary resistance set value.
ω
1
*
=
ω
r
^
+
R2
*
·
Km
*
·
Iq
*
φ
d
*
(
7
)
At the integrator
19
, a phase &thgr; is calculated by integrating the frequency command value &ohgr;1*.
Furthermore, at the speed estimation unit
21
a,
a speed estimated value &ohgr;r{circumflex over ( )} is computed based on an expression (8) using the q-axis current Iq and the d-axis secondary magnetic flux command &phgr;d*. In the expression (8) below, T1 represents a control constant used to decide estimation response.
ω
r
^
=
1
1
+
T1
·
s
×
1
Km
*
·
φ
d
*
×
{
Km
*
·
φ
d
*
·
ω
1
*
+
R1
*
·
Iq
*
-
(
R1
*
+
Km
*
2
·
R2
*
+
L
σ
*
·
s
)
·
Iq
+
Δ
Vq0
}
(
8
)
According to the control system conFIG.ured in the foregoing manner, as long as there is coincidence between a motor constant used for the primary resistance of the induction motor
6
and a motor constant used for the voltage operation unit
12
a,
the frequency operation unit
18
a
and the speed estimation unit
21
a,
then the secondary magnetic flux of the induction motor
6
is controlled to be constant, and the q-axis current Iq is set proportional to torque. Accordingly, a good control characteristic can be obtained.
As such a control method, there have been available control methods respectively described in Japanese Patent Application Laid-open Nos. 105580/1994, 284771/1994 and 317698/1996.
As a method for estimating a constant of the induction motor, there has been available a method described in Japanese Patent Application Laid-Open No. 80100/1996. According to the constant estimation method disclosed therein, when an actual value of a primary magnetic flux coincides with a set value obtained by the product of primary self-inductance and an exciting current, a constant of the induction motor can be estimated based on an error current of zero. Another method available for estimating a constant of the induction motor is one described in Japanese Patent Application Laid-Open No. 191699/1997. According to the constant estimation method disclosed t
Miller Patrick
Nappi Robert E.
LandOfFree
Control apparatus of induction motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control apparatus of induction motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control apparatus of induction motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3078552