Electricity: motive power systems – Induction motor systems
Reexamination Certificate
2001-03-06
2002-04-23
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Induction motor systems
C318S800000, C318S801000, C318S803000, C318S805000, C318S807000
Reexamination Certificate
active
06377018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a speed sensorless vector control apparatus capable of controlling the vector of an AC motor such as an induction motor, etc. without a speed sensor.
2. Description of the Related Art
In vector control known as a high-performance and high-precision system of controlling an induction motor, speed information about a motor is required, and is normally obtained by a pulse generator (PG), etc. However, it is desired to realize the speed sensor vector control as a variable speed drive system capable of performing torque control and obtaining the maximum torque in a wide operation range without a necessity of the high performance of the conventional speed sensor vector control at a request to restrict the environment of setting a speed sensor, simplify the wiring, reduce the cost, etc.
FIG. 1
is a block diagram of the function of the conventional speed sensorless vector control apparatus using a common speed adaptive secondary flux observer, and shows the speed sensor vector control of an AC motor
102
such as an induction motor, etc. by combining an inverter
101
, a current detection unit
103
, current adjustment units
104
and
105
, coordinate conversion units
106
and
109
, 3 phase to 2 phase conversion units
107
and
108
, a current/flux estimation unit
110
, and a speed estimation unit
301
.
The current/flux estimation unit
110
, the speed estimation unit
301
, etc. configure the speed adaptive secondary flux observer.
In
FIG. 1
, a primary current
118
of the AC motor
102
through the 3 phase to 2 phase conversion unit
108
is converted into a d-q axis rotation coordinate component by the coordinate conversion unit
109
with an estimated flux (vector)
122
set as the standard of a rotation coordinate, and then into a torque current (i
q
)
117
and a magnetization current (i
d
)
116
. The current adjustment units
104
and
105
perform control such that the torque current (i
q
)
117
and the magnetization current (i
d
)
116
respectively match a torque current command (i
q
*)
113
and a magnetization current command (1
d
*)
115
. The magnetization current command (1
d
*)
115
is computed by a magnetization current command operation unit
112
which receives a flux command (&PHgr;*)
114
.
The coordinate conversion unit
106
generates a primary voltage command
119
by converting the output of the current adjustment units
104
and
105
into a static coordinate system, generating a primary voltage command
119
, and providing the generated command for the inverter
101
such as a three-phase voltage type inverter, etc. The inverter
101
performs DC-AC conversion based on the primary voltage command
119
, and provides the voltage (primary voltage
120
) of each of the three phases for the AC motor
102
.
In addition, the primary voltage
120
and a primary current
118
detected by the current detection unit
103
are converted into two components respectively by the 3 phase to 2 phase conversion units
107
and
108
. The two-phase component of the primary voltage
120
is input to the current/flux estimation unit
110
, the two-phase component of the primary current
118
is input to the current/flux estimation unit
110
, the speed estimation unit
301
, and the coordinate conversion unit
109
.
Described mainly below are the operations by the current/flux estimation unit
110
and the speed estimation unit
301
to explain about the speed estimating operation in the conventional speed sensorless vector control.
First, the principle of the speed sensorless vector control is introduced by:
Document 1: Power and Electric Application Study of Electric Society of Japan, material IEA-91-11, 1991, pp. 41-48 “Speed Adaptive Secondary Flux Observer of an Induction Motor and its Characteristics”
Document 2: IEEE Transaction on Industry Application, Vol. 30, No. 5, September/October 1994, pp. 1219-1224 “Speed Sensorless Field Oriented Control of Induction Motor with Rotor Resistance Adaptation”
Document 3: “Vector Control of AC Motor” (published by Daily Industrial News in 1996, pp. 91-110, Chapter 5 ‘Speed Sensor Vector Control of Induction Motor’.
According to the above mentioned documents, the speed can be estimated based on the algorithm described below with the configuration shown in
FIG. 2
described later.
First, in an example of an induction motor as a motor to be controlled, a state equation can normally be represented by equation 1. The transposed matrix is expressed with the character T added to a matrix as a superscript.
ⅆ
/
ⅆ
t
[
i
s
φ
r
]
=
A
[
i
s
φ
r
]
+
Bv
s
i
s
=
[
i
s
α
i
s
β
]
T
;
φ
r
=
[
φ
r
α
φ
r
β
]
T
;
v
s
=
[
v
s
α
v
s
β
]
T
;
A
=
[
-
(
R
s
σ
L
s
+
1
-
σ
σ
τ
r
)
I
L
m
σ
L
s
L
r
(
1
τ
r
I
-
ω
r
J
)
L
m
τ
r
I
-
1
τ
r
I
+
ω
r
J
]
;
B
=
[
1
σ
L
s
0
0
0
0
1
σ
L
s
0
0
]
T
;
I
=
[
1
0
0
1
]
;
J
=
[
0
-
1
1
0
]
;
Equation
1
In the equation 1 above,
i
s
and v
s
indicate the primary current and the primary voltage;
&phgr;
r
indicates the secondary interlinkage flux (secondary flux);
Superscripts &agr; and &bgr; indicate the orthogonal 2-axis component s of a static coordinate system;
R
s
and R
r
indicate the primary resistance and the secondary resistance;.
L
s
, L
r
, and L
m
indicate the primary inductance, the secondary inductance, and the mutual inductance respectively;
&tgr;
r
=L
r
/R
r
indicates the secondary time constant;
&sgr;=1−L
m
2
/(L
s
L
r
) indicates a leakage coefficient; and
&ohgr;
r
indicates a rotor angular speed.
The equation 1 indicates the relationship between the primary voltage v
s
as an input to a control target and the primary current is and the secondary flux &phgr;
r
as outputs. If the primary voltage v
s
is provided, the primary current i
s
and the secondary flux &phgr;
r
can be computed.
A model in which the above mentioned deviation can be input to a simulator such that there is no deviation between an output of a control target which can be measured and an estimated output value of the simulator is referred to as a same dimensional observer. According to the principle of the observer, the current/flux estimation unit
110
computes the estimated value i
s
{circumflex over ( )} of the primary current (an estimated current
121
shown in
FIG. 1
) and the estimated value &phgr;
r
{circumflex over ( )} of the secondary flux (an estimated flux
122
) by equation 2. In the following descriptions, “{circumflex over ( )}” indicates an estimated value.
ⅆ
/
ⅆ
t
[
i
s
^
φ
r
^
]
=
A
^
[
i
s
^
φ
r
^
]
+
Bv
s
+
G
(
i
s
^
-
i
s
)
Equation
2
In the equation 2 above,
G indicates a gain matrix (optional matrix for determination of the dynamic characteristic of an observer).
A matrix A{circumflex over ( )} is obtained by replacing the angular speed &ohgr;
r
in the matrix A in the equation 1 with the estimated speed &ohgr;
r
{circumflex over ( )}.
In the equation 2 above, when the rotor angular speed changes, there arises deviation between the output (primary current estimated value) of the simulator (equation model) and the actual primary current. Thus, the speed adaptive secondary flux observer estimates the secondary flux &phgr;
r
while estimating and adapting the angular speed &ohgr;
r
using the function of the current deviation (i
s
−i
s
{circumflex over ( )}).
The speed adaptive secondary flux observer can be configured as expressed by equation 3 described later by adding the adaptive estimation mechanism of the angular speed as an unknown
Tajima Hirokazu
Umida Hidetoshi
Fuji Electric & Co., Ltd.
Greer Burns & Crain Ltd.
Leykin Rita
Nappi Robert E.
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