Electricity: motive power systems – Positional servo systems – 'reset' systems
Reexamination Certificate
2002-12-16
2004-10-26
Ip, Paul (Department: 2837)
Electricity: motive power systems
Positional servo systems
'reset' systems
C318S610000, C318S812000, C318S603000
Reexamination Certificate
active
06809492
ABSTRACT:
TECHNICAL FIELD
This invention relates to a speed control apparatus of an AC motor and in particular to improvement in characteristic in a higher-speed area than rated speed.
BACKGROUND OF THE INVENTION
In current control of an AC motor, often vector control is performed wherein the current of the AC motor is disassembled into an excitation component (which will be hereinafter referred to as d axis) and a torque component (which will be hereinafter referred to as q axis), of components on rotating Cartesian two-axis coordinates (which will be hereinafter referred to as dq-axis coordinates) and the components are controlled separately. The case of an induction motor will be discussed below as a related art.
FIG. 16
is a drawing to show the configuration of a speed control apparatus of an induction motor in a related art. In the figure, numeral
31
denotes an induction motor, numeral
32
denotes a PWM inverter for supplying electric power to the induction motor
31
based on voltage command Vu*, Vv*, Vw* described later, numerals
33
a,
33
b,
and
33
c
denote current detectors for detecting currents i
u
, i
v
, and i
w
of the induction motor
31
, and numeral
34
denotes a speed detector for detecting rotation speed &ohgr;
r
of the induction motor
31
. Numeral
35
denotes a secondary magnetic flux calculator for calculating magnetic flux &phgr;
2d
based on d-axis current i
1d
described later, numeral
36
denotes a slip frequency calculator for calculating slip angular frequency &ohgr;
s
based on q-axis current i
1q
described later and the magnetic flux &phgr;
2d
, numeral
37
denotes a coordinate rotation angular speed calculator for calculating rotation angular speed &ohgr; of dq-axis coordinates based on the slip angular frequency &ohgr;
s
calculated by the slip frequency calculator
36
and the rotation speed &ohgr;
r
of the induction motor
31
detected by the speed detector
34
, and numeral
38
denotes an integrator for integrating the rotation angular speed &ohgr; and outputting phase angle &thgr; of dq-axis coordinates. Numeral
39
denotes a three-phase to two-phase coordinate converter for disassembling the currents i
u
, i
v
, and i
w
of the current detectors
33
a,
33
b,
and
33
c
into the d-axis current i
1d
and the q-axis current i
1q
on the dq-axis coordinates based on the phase angle &thgr; of the dq-axis coordinates and outputting the d-axis current i
1d
and the q-axis current i
1q
.
Numeral
40
denotes a subtracter for outputting magnetic flux deviation e
f
between magnetic flux command &phgr;
2d
* and the magnetic flux &phgr;
2d
output by the secondary magnetic flux calculator
35
, numeral
41
denotes a magnetic flux controller for controlling proportional integration (which will be hereinafter referred to as PI) so that the magnetic flux deviation e
f
becomes 0 and outputting d-axis current component i
id
′, numeral
42
denotes a subtracter for outputting speed deviation e
w
between speed commands &ohgr;
r
* and the rotation speed &ohgr;
r
of the induction motor
31
output by the speed detector
34
, and numeral
43
denotes a speed controller for controlling PI so that the speed deviation e
w
becomes 0 and outputting q-axis current component i
1q
′.
Numeral
44
denotes a subtracter for outputting current deviation e
1d
between d-axis current command i
1d
* and d-axis current i
1d
, numeral
45
b
denotes a d-axis current controller for controlling PI so that the current deviation e
1d
becomes 0 and outputting d-axis voltage component V
d
′, numeral
46
denotes a subtracter for outputting current deviation e
1q
between q-axis current command i
1q
* and q-axis current i
1q
, numeral
47
b
denotes a q-axis current controller for controlling PI so that the current deviation e
1q
becomes 0 and outputting q-axis voltage component V
q
′, and numeral
48
denotes a two-phase to three-phase coordinate converter for converting d-axis voltage command V
d
* and q-axis voltage command V
q
* into the voltage commands Vu*, Vv*, and Vw* on the three-phase AC coordinates based on the phase angle &thgr; of the dq-axis coordinates and outputting the voltage commands as voltage commands of the PWM inverter
32
.
Numeral
51
denotes a d-axis current limiter for limiting the d-axis current component i
1d
′ within a predetermined range and outputting the d-axis current command i
1d
*, and numeral
52
denotes a q-axis current limiter for limiting the q-axis current component i
1q
′ within a predetermined range and outputting the q-axis current command i
1q
*. Numeral
53
b
denotes a d-axis voltage limiter for limiting the d-axis voltage component V
d
′ within a predetermined range and outputting the d-axis voltage command V
d
*, and numeral
54
b
denotes a q-axis voltage limiter for limiting the q-axis voltage component V
q
′ within a predetermined range and outputting the q-axis voltage command Vq*.
Numeral
55
denotes a magnetic flux command generation section for arbitrarily giving the magnetic flux command &phgr;
2d
* of the induction motor. The speed command &ohgr;
r
* is given arbitrarily from the outside.
FIG. 17
is a drawing to show the configuration of the PI controller of the magnetic flux controller
41
, the speed controller
43
, the d-axis current controller
45
b,
the q-axis current controller
47
b,
etc., in FIG.
16
. In
FIG. 17
, numeral
61
denotes a coefficient unit corresponding to proportional gain K
P
of the PI controller, numeral
62
denotes a coefficient unit corresponding to integration gain K
I
of the PI controller, numeral
63
b
denotes an integrator having a function of stopping calculation, and numeral
64
denotes an adder for adding the proportional component and the integration component.
Letter e denotes deviation input to the PI controller and U′ denotes control input output from the PI controller. As for the magnetic flux controller
41
, e corresponds to the magnetic flux deviation e
f
between the magnetic flux command &phgr;
d2
* and the magnetic flux &phgr;
2d
output by the secondary magnetic flux calculator
35
, and U′ corresponds to the d-axis current component i
1d
′. As for the speed controller
43
, a corresponds to the speed deviation e
w
between the speed command &ohgr;
r
* and the rotation speed &ohgr;
r
of the induction motor
31
output by the speed detector
34
, and U′ corresponds to the q-axis current component i
1q
′. As for the d-axis current controller
45
b,
e corresponds to the current deviation e
id
between the d-axis current command i
1d
* and the d-axis current i
1d
, and U′ corresponds to the d-axis voltage component V
d
′. As for the q-axis current controller
47
b,
e corresponds to the current deviation e
iq
between the q-axis current command i
1q
* and the q-axis current i
1q
, and U′ corresponds to the q-axis voltage component V
q
′.
The basic operation of the vector control in the induction motor will be discussed with
FIGS. 16 and 17
.
As shown in
FIG. 16
, the vector control is implemented using a plurality of PI controllers of the magnetic flux controller
41
, the speed controller
43
, the d-axis current controller
45
b,
the q-axis current controller
47
b,
etc., in combination.
The subtracter at the stage preceding each PI controller (subtracter
40
, subtracter
42
, subtracter
44
, subtracter
46
) outputs deviation e (e
f
, e
w
, e
id
, e
iq
) from the command value and actually detected value.
The PI controller is a controller for setting the deviation output from the subtracter at the predetermined stage to 0 (matching the command value and actually detected value with each other). Each PI controller inputs the deviation e output from the subtracter at the preceding stage and outputs such control input U′ (i
1d
′, i
1q
′, V
d
′, V
q
′) setting the deviation e to 0 based on the following expression (1):
U
′=(
K
P
+(
K
I
/s
))
3
·e
(1)
The block diagram of expression (1) is
Harakawa Masaya
Nagano Tetsuaki
Ip Paul
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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