Controller for multiplex winding motor

Details Controller for multiplex winding motor Controller for multiplex winding motor

2002-06-06

2004-05-04

Leykin, Rita (Department: 2837)

Electricity: motive power systems

Induction motor systems

Primary circuit control

C318S808000, C318S809000, C318S810000, C318S807000, C318S798000

Reexamination Certificate

active

06731095

ABSTRACT:

This application is based on Application No. 2001-341135, filed in Japan on Nov. 6, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a controller for a multiplex winding motor, in which the multiplex winding motor, having a plurality of independent windings in a single motor, is driven by a plurality of inverters to control rotation at variable speeds.
2. Description of the Related Art
When an alternating-current motor is driven at variable speeds, generally, an alternating-current motor having a set of multiphase (three phases in general) windings is driven by a single alternating-current power converter (inverter).
FIG. 6
shows the configuration of a current controller for an induction motor according to the above method.
In
FIG. 6
, in a main circuit, a single voltage applying means
15
is connected to an induction motor
3
including a single set of windings, and a current detector
4
for detecting the output current in the voltage applying means
15
is provided on the output side of the voltage applying means
15
. The voltage applying means
15
is composed of a PWM pulse generation circuit
5
, which outputs a PWM (Pulse Width Modulation) pulse conforming to a direct-current power supply
1
and an alternating voltage command signal v*, and a drive circuit
2
for outputting a voltage of the direct-current power supply
1
in response to a PWM pulse signal produced by the PWM pulse generation circuit
5
. The voltage applying means
15
supplies power to the induction motor
3
.
Current controlling means
6
is constituted by a two-phase sine wave generation circuit
7
, which uses a primary frequency command for an induction motor as input, uses a rotor speed of &ohgr;1* for a synchronous motor as input, and outputs a two-phase sine wave reference (phase) signal, a voltage command coordinate converter
8
for performing coordinate conversion from d-q axis component voltage commands Vd* and Vq* of a rotating coordinate system to a three-phase alternating voltage command signal v* of a stator coordinate system, a current component detecting coordinate converter
9
for performing coordinate conversion from each winding alternating current i to d-q axis component currents Id and Iq, and a current controller
11
which uses the component current commands I
d
* and I
q
* as commands and uses the d-q axis component currents Id and Iq as input. The d-q axis component currents Id and Iq are the output of the current component detecting coordinate converter
9
.
In the above current controller, a current control system is constituted, in which commands of current magnitude and phase are supplied as an exciting component current command Id*, a torque component current command Iq*, and a primary frequency command &ohgr;1*, an alternating voltage command signal v* required for each winding of the motor is computed and outputted, current i is applied to the induction motor
3
via the voltage applying means
15
, and a detected value i from the current detector
4
is used as a feedback value. An inverter
14
is constituted by the current control means
6
, the voltage applying means
15
, and the current detector
4
.
Meanwhile, when a device for driving a large-capacity alternating-current motor does not have an inverter with a capacity suitable for the capacity of the motor, a multiplex winding alternating-current motor having a plurality of sets of multiphase windings may be driven by a plurality of inverters. According to this method, an inverter having the unit capacity of
FIG. 6
can be combined according to the capacity without developing a new large-capacity inverter for large motors having different capacities. Thus, development and manufacturing of inverters can be more efficient, thereby reducing the cost. However, in this method, when current flowing in the sets of windings is unbalanced, an inverter with a larger capacity is necessary as compared with balanced current, or torque ripple and so on occurs. Hence, proposals have been made for applying constant current to sets of windings.
For example,
FIG. 7
shows a current controller for a multiplex winding motor disclosed in Japanese Patent Laid-Open No. 5-260792. In
FIG. 7
, a main circuit has two voltage applying means
15
A and
15
B connected in parallel with a multiplex winding motor
3
having two sets A and B of windings. Drive circuits
2
A and
2
B, current detectors
4
A and
4
B, and PWM pulse generation circuits
5
A and
5
B have the same functions as those of FIG.
6
.
A multiple current control means
6
is constituted by a two-phase sine wave generation circuit
7
, which uses a primary frequency command for an induction motor as input, uses a rotor speed of &ohgr;1* for a synchronous motor as input, and outputs a two-phase sine wave reference (phase) signal, voltage command coordinate converters
8
A and
8
B for performing coordinate conversion from d-q axis component voltage commands V
da
*, V
qa
*, V
db
*, and V
qb
* of a rotating coordinate system to three-phase alternating voltage command signals v
a
* and v
b
* of a stator coordinate system, current component detecting coordinate converters
9
A and
9
B for performing coordinate conversion from winding alternating currents i
a
and i
b
to d-q axis component currents I
da
, I
qa
, I
db
, and I
qb
, an average current detecting circuit
10
for computing an average value of d-q axis component currents of windings, an average current controller
11
which uses component current commands I
d
* and I
q
* as commands and inputs a deviation of average currents I
d
bar and I
q
bar, the average currents I
d
bar and I
q
bar being outputs of the average current detecting circuit
10
, a current unbalance compensating circuits
12
A and
12
B for inputting a deviation of the average currents I
d
bar and I
q
bar and d-q axis component current in windings to correct unbalanced current in windings, and adders
13
A and
13
B.
When unbalance is not found on output voltage between the drive circuits, the output of the current unbalance compensating circuits
12
A and
12
B is 0, so that output voltage is equal between the drive circuits. Meanwhile, when unbalance occurs on the output voltage between the drive circuits, unbalance occurs on the current in windings, resulting in a difference among d-q axis component currents I
da
, I
qa
, I
db
, and I
qb
. According to a deviation from an average value of the currents, the current unbalance compensating circuits
12
A and
12
B output a signal for correcting d-q axis component voltage commands of windings such that a difference in d-q axis component currents of windings is 0. Three-phase alternating current command signals v
a
* and v
b
* obtained by adding the above signals are outputted from the voltage command coordinate converters
8
A and
8
B. Thus, control is performed such that windings have equal current values.
As described above, in the controller for the conventional multiplex winding motor, a plurality of voltage applying means is controlled by a single of multiple current control means. Thus, as compared with a unit capacity inverter for a single winding that is shown in
FIG. 6
, a current control system requires a large change in configuration, and it is difficult to share the use of the current control system with a unit capacity inverter which is used independently. Hence, it has not been possible to make full use of a merit of a unit capacity inverter.
As a method for solving the above-mentioned problem, a method has been devised for controlling current in windings separately for each set. However, according to the above-mentioned current controller for the multiplex winding motor disclosed in Japanese Patent Laid-Open No. 5-260792, the above method causes torque ripple due to interference, which results from unbalance of current phases between windings, so that current control cannot be performed with fast response.
Here, the following will specifically discuss why current co

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