Electricity: motive power systems – Synchronous motor systems – Hysteresis or reluctance motor systems
Reexamination Certificate
2002-06-14
2004-04-20
Nappi, Robert (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
Hysteresis or reluctance motor systems
C318S700000
Reexamination Certificate
active
06724168
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for controlling rotation speed of a synchronous reluctance motor and particularly, to an apparatus for controlling rotation speed of a synchronous reluctance motor capable of controlling rotation speed and torque of a motor by detecting input voltage and input current of a synchronous reluctance motor and estimating speed and position angle of a rotor, without using a sensor for detecting rotor position.
2. Description of the Background Art
Generally, for a conventional apparatus for controlling rotation speed of a synchronous reluctance motor, information of speed or flux of a motor is necessary in case of performing an instantaneous torque control and accordingly, sensors such as a tachometer, generator, resolver or pulse encoder to abstract the information of speed or flux of a motor.
However, since it is difficult to handle the above sensors, the sensors are very sensitive to noise and increase cost, recently, much research about sensorless vector control methods capable of controlling speed and torque without revising the speed according to the second resistance change of a motor has been conducted actively in overseas advanced enterprises. been conducted actively in overseas advanced enterprises.
FIG. 1
is a block diagram showing structure of a conventional apparatus for controlling rotation speed of a synchronous reluctance motor and as shown in the drawing, the conventional apparatus for controlling rotation speed of a synchronous reluctance motor includes a first comparator
11
for outputting speed error after comparing a speed reference value &ohgr;
r
* and real rotor speed value &ohgr;
r
, a speed control unit
12
for outputting electric current i
qs
* for reference torque after performing PI control for compensating the outputted speed error, a second comparator
13
for outputting current error after comparing the current for reference torque i
qs
* and current for real torque i
qs
, a flux reference generation unit
14
for referring the flux and outputting flux reference value &lgr;
d
* according to the real speed &ohgr;
r
, a flux control unit
15
for outputting a current for reference flux i
ds
* after performing PI control receiving the above outputted flux reference value &lgr;
d
*, a third comparator
16
for outputting a corresponding current error by comparing the electric current for the reference flux i
ds
* and current for real flux i
ds
, a current control unit
17
for outputting voltage V
ds
* for reference flux and voltage V
qs
* for reference torque according to an output current of the second comparator
13
and third comparator
16
, a three phase voltage generation unit
18
for receiving the voltage V
ds
* for reference flux, voltage V
qs
* for reference torque and the real position angle of the rotor &thgr; from the integrator
22
, converting into three phase voltages Vas, Vbs and Vcs of the fixed coordinate system and outputting the voltages, an inverter unit
19
for rotating the synchronous reluctance motor
20
by applying the three phase voltages Vas, Vbs and Vcs of the three phase voltage generation unit
18
, a rotor position detection unit
21
for yielding the real speed by detecting rotation speed of the synchronous reluctance motor, an integrator
22
for yielding the real position angle of the rotor by integrating the real speed &ohgr;
r
and a coordinate conversion unit
23
for receiving the two phase electric currents ias and ics detected in rotating the synchronous reluctance motor
20
, converting the currents into the current i
ds
for real flux and current i
qs
for real torque and outputting the converted currents.
Here, operation principle of the conventional apparatus for controlling rotation speed of a synchronous reluctance motor with reference to the accompanied drawings is as follows.
First, the first comparator
11
outputs speed error to the speed control unit
12
after comparing a speed reference value &ohgr;
r
* and real rotor speed value &ohgr;
r
detected from the rotor position detection unit
18
in rotating the synchronous reluctance motor
17
. Then, the speed control unit
12
outputs electric current i
qs
* for reference torque after performing PI control for compensating the outputted speed error.
On the other hand, the flux reference generation unit
14
generates and outputs the flux reference value &lgr;
d
* to the flux control unit
15
and the flux control unit
15
outputs the current i
ds
* for reference flux to third comparator
16
after performing PI control by receiving the above outputted flux reference value &lgr;
d
*.
The third comparator
16
outputs the corresponding current error to the current control unit
17
by comparing the electric current i
ds
* for the reference flux generated and outputted according to the outputted flux reference value &lgr;
d
* and current i
ds
for real flux outputted to the coordinate conversion unit
20
. Then, the current control unit
17
generates the voltage V
ds
* for reference flux and voltage V
qs
* for reference torque, which are respectively D-axis voltage and Q-axis voltage by receiving the current errors outputted from the second comparator
13
and third comparator
16
and outputs the voltages to the three phase voltage generation unit
15
.
Here, a formula for yielding the voltage V
ds
* for reference flux and voltage V
qs
* for reference torque is as follows:
V
d
=
R
s
i
d
+
L
d
ⅆ
i
d
ⅆ
t
-
ω
e
L
q
i
q
V
q
=
R
s
i
q
+
L
d
ⅆ
i
q
ⅆ
t
-
ω
e
L
d
i
d
Formula
1
Here, V
d
, V
q
are respectively components of D-axis and Q-axis of voltage, i
d
, i
q
are respectively components of the D-axis and Q-axis of current, R
s
is resistance of stator side and L
d
, L
q
are inductances of the D-axis and Q-axis.
Then, the three phase voltage generation unit
18
generates three phase voltages Vas, Vbs and Vcs of the fixed coordinate system using the voltage V
ds
* for reference flux, voltage V
qs
* for reference torque and the real position angle of the rotor &thgr; from the integrator
22
and applies the voltages into the inverter unit
19
and the inverter unit
19
applying the three phase voltages Vas, Vbs and Vcs into the synchronous reluctance motor
20
.
At this time, the rotor position detection unit
21
for detecting the rotor position of the synchronous reluctance motor
20
outputs the real rotation speed of the detected motor into the first comparator
11
and the integrator
22
. Then, the integrator
22
yields the position angle of the rotor (&thgr;) corresponding to the real position of the rotor by integrating the real speed and outputs the angle into the coordinate conversion unit
23
and three phase voltage generation units
18
.
Therefore, the conventional synchronous reluctance motor controls rotation speed of the motor by repeatedly performing the above process.
However, the conventional apparatus with the above operation, includes a torque ripple due to harmonic wave components included in the detected fundamental wave of current frequency, switching dead time and the like and accordingly, harmonic wave components are included in the induced voltage. Therefore, a ripple is generated in an estimated-calculated rotation speed and accordingly, precise speed control was not possible. Also, it was difficult to handle the apparatus by using an encoder and hall-sensor of the rotor position detection unit.
Also, the conventional apparatus for controlling rotation speed of a synchronous reluctance motor has problems that the cost increases due to using a costly rotor position detection unit and low speed control can not be smoothly done in spite of excellent high speed control.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to control a low speed area and high speed area separately to maintain precision of speed control according to variation of load in sensorless speed control for detecting rotor position of a synchronous reluct
Cheong Dal-Ho
Lee Kyung-Hoon
Oh Jae-Yoon
LG Electronics Inc.
Miller Patrick
Nappi Robert
LandOfFree
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