FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
CONTROL DEVICE FOR ROTARY MACHINE
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
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DESCRIPTION
TITLE OF THE INVENTION: CONTROL DEVICE FOR ROTARY MACHINE
TECHNICAL FIELD
[0001] The present disclosure relates to a control device5
for a rotary machine.
BACKGROUND ART
[0002] A control device for a rotary machine having a
field winding and a stator winding generates current commands10
for currents flowing through the field winding and the stator
winding, in accordance with operation commands for torque, a
rotational speed, and the like of the rotary machine, which
are inputted from the outside. The control device for the
rotary machine performs control so that currents flowing15
through the field winding and the stator winding follow the
current commands. In general, the impedance of the field
winding is greater than the impedance of the stator winding,
and thus it is known that response of the current flowing
through the field winding is slower than response of the20
current flowing through the stator winding. Therefore, in
order to appropriately control the rotary machine, the
conventional control device for the rotary machine performs
control while taking into consideration the fact that current
response of the field winding is slower than current response25
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of the stator winding.
[0003] In one conventional control method for a rotary
machine, a current command for a stator winding is calculated
on the basis of variation in torque caused by variation in
delay of current response of a field winding (see, for5
example, Patent Document 1). In another control method,
response delay of current of a field winding with respect to
a current command is simulated, and a current command for a
stator winding is calculated on the basis of the simulated
response delay (see, for example, Patent Document 2).10
CITATION LIST
PATENT DOCUMENT
[0004] Patent Document 1: Japanese Laid-Open Patent
Publication No. 2022-8390515
Patent Document 2: WO2020/217438
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0005] However, in such conventional control methods for a20
rotary machine, in a case where delay of current response of
the field winding is slower than assumed, or in a case where
current actually flowing through a stator winding cannot
follow a current command for the stator winding because of
variation in specifications, the amplitude of the current25
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command for the stator winding might become greater than
assumed. In this case, if the amplitude of the current
command for the stator winding exceeds an upper limit value
of voltage that the control device can output, a voltage
command might be saturated. If the voltage command is5
saturated, windup of integral control in the control device,
magnetic flux interference between the stator winding and the
field winding in the rotary machine, and the like are caused.
As a result, current control for the rotary machine becomes
unstable.10
[0006] The present disclosure has been made to solve the
above problem, and an object of the present disclosure is to
provide a control device for a rotary machine that can
perform stable current control while suppressing saturation
of a voltage command for a stator winding, even in a case15
where the amplitude of a current command for the stator
winding might become greater than assumed.
MEANS TO SOLVE THE PROBLEM
[0007] A control device for a rotary machine according to20
the present disclosure is a control device for a rotary
machine including a rotor having a field winding and a stator
having a stator winding, the control device including: a
current command generation unit which generates a field
winding current command for field winding current and a25
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stator winding current command for stator winding current, on
the basis of an operation command inputted from outside; a
field winding voltage command unit which generates a field
winding voltage command for voltage to be applied to the
field winding, on the basis of the field winding current5
command; a stator winding voltage command unit which
generates a stator winding voltage command for voltage to be
applied to the stator winding, on the basis of the stator
winding current command; a field winding power conversion
unit which applies voltage to the field winding on the basis10
of the field winding voltage command; and a stator winding
power conversion unit which applies voltage to the stator
winding on the basis of the stator winding voltage command.
The current command generation unit includes: a current
command calculation unit which calculates the field winding15
current command and the stator winding current command on the
basis of the operation command and DC voltage inputted from
outside; an allowable magnetic flux calculation unit which
calculates an allowable magnetic flux which is an allowable
value of a magnetic flux interlinking the stator winding, on20
the basis of a rotational speed of the rotary machine, the DC
voltage, the stator winding current command, and the field
winding current; a first flux weakening current calculation
unit which calculates first flux weakening current on the
basis of the field winding current, the stator winding25
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current command, and the allowable magnetic flux; and a final
current command calculation unit which calculates the stator
winding current command that is final, on the basis of the
stator winding current command and the first flux weakening
current.5
EFFECT OF THE INVENTION
[0008] In the control device for the rotary machine
according to the present disclosure, the current command
generation unit includes: the current command calculation10
unit which calculates the field winding current command and
the stator winding current command on the basis of the
operation command and DC voltage inputted from outside; the
allowable magnetic flux calculation unit which calculates the
allowable magnetic flux which is an allowable value of a15
magnetic flux interlinking the stator winding, on the basis
of the rotational speed of the rotary machine, the DC
voltage, the stator winding current command, and the field
winding current; the first flux weakening current calculation
unit which calculates first flux weakening current on the20
basis of the field winding current, the stator winding
current command, and the allowable magnetic flux; and the
final current command calculation unit which calculates the
stator winding current command that is final, on the basis of
the stator winding current command and the first flux25
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weakening current. Thus, it is possible to perform stable
current control while suppressing saturation of the voltage
command for the stator winding.
BRIEF DESCRIPTION OF THE DRAWINGS5
[0009] [FIG. 1] FIG. 1 is a configuration diagram of a
control device for a rotary machine according to embodiment
1.
[FIG. 2] FIG. 2 is a configuration diagram of a
stator winding power conversion unit according to embodiment10
1.
[FIG. 3] FIG. 3 is a configuration diagram of a
field winding power conversion unit according to embodiment
1.
[FIG. 4] FIG. 4 is a configuration diagram of a15
field winding power conversion unit according to embodiment
1.
[FIG. 5] FIG. 5 is a configuration diagram showing
a function of a processor according to embodiment 1.
[FIG. 6] FIG. 6 is a configuration diagram showing20
a function of a current command generation unit according to
embodiment 1.
[FIG. 7] FIG. 7 shows a relationship of a q-axis
magnetic flux with respect to d-axis current and q-axis
current at specific field winding current in the rotary25
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machine according to embodiment 1.
[FIG. 8] FIG. 8 shows a relationship of d-axis
current with respect to a d-axis magnetic flux and q-axis
current at specific field winding current in the rotary
machine according to embodiment 1.5
[FIG. 9] FIG. 9 is a configuration diagram showing
the function of a current command generation unit according
to embodiment 2.
DESCRIPTION OF EMBODIMENTS10
[0010] Hereinafter, a control device for a rotary machine
according to embodiments for carrying out the present
disclosure will be described in detail with reference to the
drawings. In the drawings, the same reference characters
denote the same or corresponding parts.15
[0011] Embodiment 1
FIG. 1 is a configuration diagram of a control
device for a rotary machine according to embodiment 1. A
control device 1 for a rotary machine according to the
present embodiment controls a rotary machine 2. The control20
device 1 is driven by DC voltage of an external DC power
supply 3. The control device 1 includes a stator winding
power conversion unit 4, a field winding power conversion
unit 5, a stator winding current detection unit 6 which
detects current flowing through a stator winding, a field25
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winding current detection unit 7 which detects current
flowing through a field winding, a processor 8, and a storage
device 9. The control device 1 for the rotary machine
according to the present embodiment controls the rotary
machine 2 on the basis of operation commands inputted from a5
host device. The operation commands inputted from the host
device are, for example, a torque command for determining
torque of the rotary machine 2, a rotational speed command
for determining a rotational speed thereof, and the like.
[0012] The rotary machine 2 includes a rotor having a10
permanent magnet and the field winding, and a stator having
one set of stator windings for three phases, i.e., U phase, V
phase, and W phase. The rotor may not necessarily have a
permanent magnet. The stator windings are not limited to a
configuration of having one set of three phases, and a15
configuration of having one or more sets of three or more
phases may be adopted.
[0013] The stator winding power conversion unit 4 converts
DC voltage of the DC power supply 3 to AC voltage, and
applies AC voltage to the stator windings. The field winding20
power conversion unit 5 converts DC voltage of the DC power
supply 3 to DC voltage having a different amplitude, and
applies the DC voltage as field winding voltage Vf to the
field winding. The stator winding current detection unit 6
detects currents flowing through the stator windings for U25
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phase, V phase, and W phase of the rotary machine 2. The
field winding current detection unit 7 detects current
flowing through the field winding of the rotary machine 2.
[0014] FIG. 2 is a configuration diagram of the stator
winding power conversion unit according to the present5
embodiment. FIG. 2 shows an example of the stator winding
power conversion unit 4 in the present embodiment. As shown
in FIG. 2, the stator winding power conversion unit 4 in the
present embodiment is a three-phase full-bridge inverter
composed of six switching elements and six diodes. The10
configuration of the stator winding power conversion unit 4
is a configuration for a case where the rotary machine has
one set of stator windings for three phases, i.e., U phase, V
phase, and W phase. Each switching element is formed of a
MOS-FET (metal oxide semiconductor-field effect transistor),15
an IGBT (insulated gate bipolar transistor), or the like.
The stator winding power conversion unit 4 applies AC
voltages to the stator windings for U phase, V phase, and W
phase of the rotary machine 2 in accordance with a stator
winding switching command inputted from the processor 8.20
Specifically, the stator winding power conversion unit 4
applies AC voltages according to switching commands UH and UL
for U phase, switching commands VH and VL for V phase, and
switching commands WH and WL for W phase from the processor
8, to the stator windings for U phase, V phase, and W phase25
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of the rotary machine 2. The stator winding power conversion
unit 4 is not limited to an inverter, and may be a converter.
The configuration of the inverter of the stator winding power
conversion unit 4 may be any configuration having one or more
sets of three or more phases in accordance with the number of5
phases of the stator windings of the rotary machine 2.
[0015] FIG. 3 is a configuration diagram of the field
winding power conversion unit according to the present
embodiment. FIG. 3 shows an example of the field winding
power conversion unit 5 in the present embodiment. As shown10
in FIG. 3, the field winding power conversion unit 5 in the
present embodiment is a two-phase full-bridge converter
composed of four switching elements and four diodes. Each
switching element is formed of a MOS-FET, an IGBT, or the
like. The field winding power conversion unit 5 applies DC15
voltage to the field winding of the rotary machine 2 in
accordance with a field winding switching command inputted
from the processor 8. Specifically, the field winding power
conversion unit 5 converts DC voltage inputted from the DC
power supply 3 to DC voltage having a different amplitude in20
accordance with switching commands F1H, F1L, F2H, F2L for the
field winding from the processor 8, and applies the converted
DC voltage to the field winding of the rotary machine 2. For
example, in a case where a torque command inputted to the
processor 8 is a command for increasing an amplitude, the25
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field winding power conversion unit 5 controls application
voltage so that current of the field winding increases in the
positive direction. Conversely, in a case where a torque
command inputted to the processor 8 is a command for
decreasing an amplitude, the field winding power conversion5
unit 5 controls application voltage so that current of the
field winding increases in the negative direction.
[0016] FIG. 4 is a configuration diagram of the field
winding power conversion unit according to the present
embodiment. FIG. 4 shows another example of the field10
winding power conversion unit 5 in the present embodiment.
As shown in FIG. 4, the field winding power conversion unit 5
is configured such that, in the field winding power
conversion unit shown in FIG. 3, the switching elements for
applying voltage in the negative direction to the field15
winding are replaced with diodes. Therefore, this field
winding power conversion unit 5 is reduced in cost as
compared to the field winding power conversion unit shown in
FIG. 3. However, this field winding power conversion unit 5
cannot apply voltage in the negative direction to the field20
winding. Therefore, in a case where a torque command is to
decrease an amplitude, current response of the field winding
greatly depends on a time constant of a resistance and an
inductance of the field winding, and thus the current
response of the field winding is extremely slow as compared25
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to current response of the stator winding.
[0017] The stator winding current detection unit 6 and the
field winding current detection unit 7 are, for example,
current sensors of a resistance detection type, a magnetic
field detection type, or the like. The stator winding5
current detection unit 6 detects stator winding currents IU,
IV, IW flowing through the stator windings for U phase, V
phase, and W phase of the rotary machine 2. The field
winding current detection unit 7 detects field winding
current If flowing through the field winding of the rotary10
machine 2.
[0018] The processor 8 is, for example, a CPU (Central
Processing Unit), and executes a program read from the
storage device 9, to implement various functions. The
program to be executed by the processor 8 is stored in the15
storage device 9. The storage device 9 includes a volatile
storage device such as a random access memory and an
auxiliary storage device such as a flash memory. When the
processor 8 reads the program from the storage device 9, the
processor 8 reads the program stored in the auxiliary storage20
device via the volatile storage device. The processor 8 may
output data such as a calculation result to the volatile
storage device of the storage device 9, or may store such
data into the auxiliary storage device via the volatile
storage device.25
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[0019] FIG. 5 is a configuration diagram showing a
function of the processor. As shown in FIG. 5, the processor
8 includes a current command generation unit 81, a stator
winding voltage command unit 82, a stator winding switching
command generation unit 83, a field winding voltage command5
unit 84, and a field winding switching command generation
unit 85.
[0020] The current command generation unit 81 receives
operation commands such as a torque command and a rotational
speed command, DC voltage of the DC power supply 3, the10
stator winding currents IU, IV, IW detected by the stator
winding current detection unit 6, and the field winding
current If detected by the field winding current detection
unit 7. The current command generation unit 81 generates
final stator winding current commands Idtgt, Iqtgt and a field15
winding current command Ifref on the basis of the above
inputs. Here, a d axis is an axis representing the direction
of a magnetic flux interlinking the stator by the permanent
magnet and the field winding of the rotor, and a q axis is an
axis orthogonal to the d axis. Hereinafter, indices d and q20
attached to notations of current and voltage mean the d axis
and the q axis, respectively.
[0021] On the basis of the final stator winding current
commands Idtgt, Iqtgt generated by the current command
generation unit 81 and the stator winding currents IU, IV, IW25
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detected by the stator winding current detection unit 6, the
stator winding voltage command unit 82 generates stator
winding voltage commands so that stator winding currents
follow the final stator winding current commands. At this
time, the stator winding voltage command unit 82 performs5
coordinate conversion of the stator winding currents IU, IV,
IW to Id, Iq on the basis of rotor position information of the
rotary machine 2, and then calculates final voltage commands
Vdtgt, Vqtgt using decoupling control and PI (Proportional-
Integral) control so that Id and Iq follow Idtgt and Iqtgt.10
Further, the stator winding voltage command unit 82 converts
Vdtgt and Vqtgt through coordinate conversion to stator winding
voltage commands VU, VV, VW. The rotor position information
of the rotary machine 2 can be detected by means such as a
resolver or an encoder attached to the rotary machine 2,15
although not shown. Alternatively, rotor position
information estimated by a rotor position estimator may be
used as the rotor position information of the rotary machine
2. The rotational speed of the rotary machine 2 can be
obtained from temporal change in rotor position information.20
[0022] The stator winding switching command generation
unit 83 performs pulse width modulation on the stator winding
voltage commands VU, VV, VW calculated by the stator winding
voltage command unit 82, to generate the switching commands
UH and UL for U phase, the switching commands VH and VL for V25
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phase, and the switching commands WH and WL for W phase,
which have pulse widths according to the stator winding
voltage commands. The stator winding switching command
generation unit 83 outputs the generated switching commands
to the stator winding power conversion unit 4.5
[0023] On the basis of the field winding current command
Ifref generated by the current command generation unit 81 and
the field winding current If detected by the field winding
current detection unit 7, the field winding voltage command
unit 84 generates a field winding voltage command so that the10
field winding current follows the field winding current
command. At this time, the field winding voltage command
unit 84 calculates the field winding voltage command Vfref
using PI control so that the field winding current If follows
the field winding current command Ifref.15
[0024] The field winding switching command generation unit
85 performs pulse width modulation on the field winding
voltage command Vfref calculated by the field winding voltage
command unit 84, to generate a switching command having a
pulse width according to the field winding voltage command.20
In a case where the field winding power conversion unit 5 has
the configuration shown in FIG. 3, the field winding
switching command generation unit 85 generates the switching
commands F1H, F1L and F2H, F2L. In a case where the field
winding power conversion unit 5 has the configuration shown25
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in FIG. 4, the field winding switching command generation
unit 85 generates the switching commands F1H, F1L. Then, the
field winding switching command generation unit 85 outputs
the generated switching commands to the field winding power
conversion unit 5.5
[0025] FIG. 6 is a configuration diagram showing the
function of the current command generation unit. As shown in
FIG. 6, the current command generation unit 81 includes a
current command calculation unit 810, an allowable magnetic
flux calculation unit 811, a first flux weakening current10
calculation unit 812, and a final current command calculation
unit 813.
[0026] The current command calculation unit 810 receives a
torque command, a rotational speed, and DC voltage. The
current command calculation unit 810 has a lookup table15
having combinations of a torque command, a rotational speed,
DC voltage, and the stator winding current commands Idref,
Iqref and the field winding current command Ifref that maximize
efficiency. On the basis of the lookup table, the current
command calculation unit 810 calculates the stator winding20
current commands Idref, Iqref and the field winding current
command Ifref that maximize efficiency. The current command
calculation unit 810 may not necessarily use a lookup table
to generate the stator winding current commands and the field
winding current command. The current command calculation25
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unit 810 may calculate the stator winding current commands
and the field winding current command on the basis of a
relational equation among a torque command, a rotational
speed, DC voltage, the stator winding current commands, and
the field winding current command. In a case where a5
rotational speed command is provided as an operation command,
the rotational speed command may be used instead of the
rotational speed.
[0027] The allowable magnetic flux calculation unit 811
receives the stator winding current commands Idref, Iqref, the10
torque command, the rotational speed, and the field winding
current If. The allowable magnetic flux calculation unit 811
calculates a d-axis component φdlim of an allowable magnetic
flux on the basis of the stator winding current command, the
torque command, the rotational speed, and the field winding15
current If, using Formulae (1) to (16) described below.
[0028] Voltage equations in a steady state are represented
by the following Formula (1), using d-axis voltage Vd, q-axis
voltage Vq, d-axis current Id, q-axis current Iq, a d-axis
magnetic flux φd, a q-axis magnetic flux φq, and an20
electrical angular velocity ω.
[0029] [Mathematical 1]
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[0030] The d-axis magnetic flux φd and the q-axis magnetic
flux φq can be represented by functions of the d-axis current
Id, the q-axis current Iq, and the field winding current If,
as shown by the following Formula (2).5
[0031] [Mathematical 2]
[0032] FIG. 7 shows a relationship of the q-axis magnetic
flux with respect to d-axis current and q-axis current at
specific field winding current. FIG. 7 shows a relationship10
represented by the lower equation in Formula (2) at specific
field winding current. As shown in FIG. 7, change in the q-
axis magnetic flux with respect to d-axis current is small,
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whereas change in the q-axis magnetic flux with respect to q-
axis current is great. Although a graph corresponding to the
upper equation in Formula (2) is not shown, change in the d-
axis magnetic flux with respect to q-axis current is small,
whereas change in the d-axis magnetic flux with respect to d-5
axis current is great.
[0033] There is a limit on voltage that can be applied to
the stator winding based on the DC voltage Vdc outputted from
the DC power supply 3. Therefore, d-axis voltage and q-axis
voltage are limited by limit voltage Vmax, and the sum of10
squares of d-axis voltage and q-axis voltage needs to satisfy
the following Formula (3). That is, by reducing the absolute
value of the second term on the right-hand side of Formula
(1), it is possible to suppress voltage saturation.
[0034] [Mathematical 3]15
[0035] The limit voltage Vmax is represented by the
following Formula (4) using a voltage utilization factor K.
The voltage utilization factor K is 0.707 when operation is
performed at the maximum amplitude that allows line voltage20
to keep a sinewave, and 0.78 when operation is performed with
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a rectangular wave applied.
[0036] [Mathematical 4]
[0037] By substituting Formula (1) into Formula (3), the
following Formula (5) is obtained.5
[0038] [Mathematical 5]
[0039] In a region in which there is concern about voltage
saturation, the following Formula (6) is often satisfied.
[0040] [Mathematical 6]10
[0041] From Formula (5), upper limits of the d-axis
magnetic flux and the q-axis magnetic flux are determined by
limit voltage. Therefore, as the rotational speed increases,
it is necessary to suppress the absolute value of the d-axis15
magnetic flux or the absolute value of the q-axis magnetic
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flux. The absolute value of the d-axis magnetic flux can be
reduced by setting the d-axis current in the negative
direction, and the absolute value of the q-axis magnetic flux
can be reduced by making the absolute value of the q-axis
current small.5
[0042] Since the d-axis magnetic flux φd and the q-axis
magnetic flux φq change with d-axis current and q-axis
current, the third term in Formula (5) is not originally
determined in a state in which d-axis current and q-axis
current are indefinite. However, since the relation of10
Formula (6) is satisfied, a d-axis magnetic flux temporary
value φd_tmp and a q-axis magnetic flux temporary value φq_tmp
which can be calculated by the following Formula (7) from the
d-axis current command and the q-axis current command may be
used for the right-hand side of Formula (5).15
By rearranging Formula (5) using the d-axis
magnetic flux temporary value φd_tmp and the q-axis magnetic
flux temporary value φq_tmp shown in Formula (7), upper limits
of the d-axis magnetic flux and the q-axis magnetic flux are
represented by the following Formula (8). By using field20
winding current that satisfies Formula (8), accuracy of the
d-axis magnetic flux temporary value and the q-axis magnetic
flux temporary value can be improved. The allowable magnetic
flux calculation unit 811 may have, as a map or a function,
fd and fq representing the relationship between the stator25
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winding current commands Idref, Iqref and the field winding
current If, and the d-axis magnetic flux temporary value φd_tmp
and the q-axis magnetic flux temporary value φq_tmp, shown in
Formula (7).
[0043] [Mathematical 7]5
[Mathematical 8]
[0044] In a case of suppressing voltage saturation through
control for d-axis current, the d-axis magnetic flux is10
limited so as to be weakened. Since the q-axis magnetic flux
changes less in the d-axis direction, the d-axis magnetic
flux is caused to satisfy the following Formula (9).
[0045] [Mathematical 9]
15
[0046] That is, if the d-axis magnetic flux satisfies
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Formula (9), voltage saturation can be suppressed.
Therefore, where an allowable amount of a magnetic flux with
respect to voltage saturation is defined as an allowable
magnetic flux, the d-axis component φdlim of the allowable
magnetic flux can be calculated by the following Formula5
(10).
[0047] [Mathematical 10]
[0048] Here, if d-axis current is excessively reduced in
the negative direction, the d-axis magnetic flux becomes10
negative. Therefore, in order to suppress voltage
saturation, the d-axis current needs to be set in a range
shown by the following Formula (11), using a d-axis current
lower limit value Idmin. The d-axis current lower limit value
Idmin tends to monotonously increase with respect to the field15
winding current.
[0049] [Mathematical 11]
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[0050] The d-axis current lower limit value Idmin is set to
d-axis current at which the d-axis magnetic flux becomes 0.
Alternatively, the d-axis current lower limit value Idmin may
be set to -1 times a current upper limit value Idqmax that can
be applied to the stator winding power conversion unit and5
the rotary machine. Here, the current upper limit value Idqmax
is an upper limit value of the root sum square of d-axis
current and q-axis current, which is determined on the basis
of the rotary machine 2 and the stator winding power
conversion unit 4.10
[0051] Accordingly, the d-axis component φdlim of the
allowable magnetic flux can be calculated by the following
Formula (13) using a second q-axis magnetic flux temporary
value φq_tmp2 shown in the following Formula (12) considering
Formula (11). The allowable magnetic flux calculation unit15
811 may have, as a map or a function, fq representing the
relationship between the second q-axis magnetic flux
temporary value φq_tmp2, and the d-axis current lower limit
value Idmin, the stator winding current command Iqref for the q
axis, and the field winding current If, shown in Formula20
(12).
[0052] [Mathematical 12]
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[Mathematical 13]
[0053] Output torque T of the rotary machine is
represented by the following Formula (14), using Pm which is5
the number of poles of the rotary machine.
[0054] [Mathematical 14]
[0055] In a case where a torque command Tref is provided as
an operation command, the d-axis component φdlim of the10
allowable magnetic flux can be calculated by the following
Formula (15). By utilizing the provided torque command,
calculation of the third term on the right-hand side can be
simplified, so that the processing load can be reduced.
[0056] [Mathematical 15]15
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[0057] The d-axis component φdlim of the allowable magnetic
flux can be calculated by the following Formula (16) having
the d-axis current lower limit value Idmin in the second term
on the right-hand side. By using the d-axis current lower5
limit value instead of the d-axis component of the stator
winding current command, a calculation formula in which the
present state is more reflected is obtained.
[0058] [Mathematical 16]
10
[0059] Thus far, the case of limiting the d-axis component
of the allowable magnetic flux in the allowable magnetic flux
calculation unit 811 in the weakening direction, has been
described. Alternatively, in the allowable magnetic flux
calculation unit 811, a q-axis component of the allowable15
magnetic flux may be limited in the weakening direction. For
example, the allowable magnetic flux calculation unit 811 may
calculate the q-axis component φqlim of the allowable magnetic
flux using the following Formula (17) or (18), or the like.
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Calculating the q-axis component φqlim of the allowable
magnetic flux in the allowable magnetic flux calculation unit
811 is effective in a case where voltage saturation cannot be
suppressed even if d-axis current is reduced to a d-axis
current lower limit value, particularly in a region where the5
rotational speed of the rotary machine is great.
[0060] [Mathematical 17]
[0061] [Mathematical 18]
10
[0062] The first flux weakening current calculation unit
812 receives the field winding current, the stator winding
current command, and the allowable magnetic flux. The first
flux weakening current calculation unit 812 calculates first
flux weakening current on the basis of the field winding15
current, the stator winding current command, and the
allowable magnetic flux, using Formulae (19) to (22)
described below.
[0063] In a case where the d-axis component φdlim of the
allowable magnetic flux is obtained, the first flux weakening20
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current calculation unit 812 calculates a d-axis component
Id_fw of the first flux weakening current by the following
Formula (19). The first flux weakening current calculation
unit 812 may perform lower limit clip processing on the d-
axis component Id_fw of the first flux weakening current by5
the d-axis current lower limit value Idmin.
[0064] [Mathematical 19]
[0065] FIG. 8 shows a relationship of d-axis current with
respect to q-axis current and a d-axis magnetic flux which is10
a d-axis component of the allowable magnetic flux at specific
field winding current. FIG. 8 shows a relationship
represented by Formula (19) at specific field winding
current. The first flux weakening current calculation unit
812 may have, as a map or a function, gd representing the15
relationship between d-axis current, and the field winding
current, the d-axis magnetic flux which is the d-axis
component of the allowable magnetic flux, and q-axis current,
shown in FIG. 8.
[0066] In a case where the q-axis component φqlim of the20
allowable magnetic flux is obtained, the first flux weakening
current calculation unit 812 calculates a q-axis component
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Iq_fw of the first flux weakening current by the following
Formula (20). The first flux weakening current calculation
unit 812 may have, as a map or a function, gq representing
the relationship between d-axis current, and the field
winding current, the q-axis magnetic flux which is the q-axis5
component of the allowable magnetic flux, and q-axis current.
The first flux weakening current calculation unit 812 may
perform upper limit clip processing on the q-axis component
Iq_fw of the first flux weakening current by the current upper
limit value Idqmax.10
[0067] [Mathematical 20]
[0068] In a case where both of the d-axis component φdlim
and the q-axis component φqlim of the allowable magnetic flux
are obtained, the first flux weakening current calculation15
unit 812 calculates the d-axis component Id_fw of the first
flux weakening current by Formula (19) and calculates the q-
axis component Iq_fw of the first flux weakening current by
the following Formula (21). The first flux weakening current
calculation unit 812 may have, as maps or functions, gd20
representing the relationship between d-axis current, and the
field winding current, the d-axis component of the allowable
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magnetic flux, and q-axis current, and gq representing the
relationship between q-axis current, and the field winding
current, the q-axis component of the allowable magnetic flux,
and d-axis current. The first flux weakening current
calculation unit 812 may perform upper limit clip processing5
on the d-axis component Id_fw and the q-axis component Iq_fw of
the first flux weakening current by the current upper limit
value Idqmax.
[0069] [Mathematical 21]
10
[0070] In a case where the d-axis component φdlim of the
allowable magnetic flux is not obtained, the first flux
weakening current calculation unit 812 sets the d-axis
component of the first flux weakening current to Idref. In a
case where the q-axis component φqlim of the allowable15
magnetic flux is not obtained, the first flux weakening
current calculation unit 812 calculates the q-axis component
of the first flux weakening current by the following Formula
(22).
[0071] [Mathematical 22]20
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[0072] The final current command calculation unit 813
receives the stator winding current command and the first
flux weakening current. The final current command
calculation unit 813 calculates a final stator winding5
current command on the basis of the stator winding current
command and the first flux weakening current, using Formulae
(23) to (25) described below.
[0073] In a case where voltage saturation needs to be
suppressed, Id_fw becomes smaller than the d-axis component10
Idtgt of the final stator winding current command. Therefore,
the final current command calculation unit 813 calculates the
d-axis component Idtgt of the final stator winding current
command by the following Formula (23).
[0074] [Mathematical 23]15
[0075] In a case where voltage saturation needs to be
suppressed, the absolute value of Iq_fw becomes smaller than
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that of the q-axis component Iqtgt of the final stator winding
current command. Therefore, in a case where Iqref is
positive, the final current command calculation unit 813
calculates the q-axis component Iqtgt of the final stator
winding current command by the following Formula (24). In a5
case where Iqref is negative, the final current command
calculation unit 813 calculates the q-axis component Iqtgt of
the final stator winding current command by the following
Formula (25).
[0076] [Mathematical 24]10
[0077] [Mathematical 25]
[0078] In the control device for the rotary machine
configured as described above, on the basis of the final15
stator winding current commands Iqtgt and Iqtgt, the stator
winding voltage command unit generates the stator winding
voltage commands so that the stator winding currents follow
the final stator winding current commands. Thus, windup of
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integral control, unexpected magnetic flux interference
between the stator winding and the field winding in the
rotary machine, and the like can be suppressed. As a result,
the control device for the rotary machine according to the
present embodiment can perform stable current control while5
suppressing saturation of the voltage command for the stator
winding. Here, windup of integral control means a phenomenon
in which there is a great deviation between a target value
and a present value in integral control and the deviation is
added to an extent exceeding a saturation limit, so that it10
becomes difficult to respond immediately when the deviation
is inverted.
[0079] Embodiment 2
FIG. 9 is a configuration diagram showing the
function of a current command generation unit of a control15
device for a rotary machine according to embodiment 2. The
configuration of the control device for the rotary machine
according to the present embodiment is the same as that shown
in FIG. 1 in embodiment 1. The function configuration of the
processor in the control device for the rotary machine20
according to the present embodiment is also the same as that
shown in FIG. 5 in embodiment 1. In the control device for
the rotary machine according to the present embodiment, the
configuration of the current command generation unit inside
the processor is different from that of the current command25
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generation unit in embodiment 1.
[0080] As shown in FIG. 9, the current command generation
unit 81 in the present embodiment additionally includes a
second flux weakening current calculation unit 814 and a
final flux weakening current determination unit 815 in the5
current command generation unit shown in FIG. 6 in embodiment
1.
[0081] The second flux weakening current calculation unit
814 receives DC voltage and application voltage. Here, the
application voltage is application voltage to the stator10
winding, calculated from the stator winding voltage command
outputted from the stator winding voltage command unit. In a
case where the application voltage is greater than DC
voltage, the second flux weakening current calculation unit
814 determines that voltage is saturated, and performs15
feedback of a deviation between the application voltage and
the DC voltage, to calculate second flux weakening current.
For example, the second flux weakening current calculation
unit 814 has a high-frequency amplifier, a subtractor, and a
compensator. The high-frequency amplifier calculates20
correction application voltage by amplifying a high-frequency
component of the inputted application voltage. The
subtractor subtracts the correction application voltage from
target application voltage determined by a target voltage
utilization factor and the DC voltage, to calculate a voltage25
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deviation. The compensator calculates the second flux
weakening current on the basis of the voltage deviation
calculated by the subtractor.
[0082] The first flux weakening current calculation unit
812 is suitable for a case where flux weakening current is5
immediately needed when an operation command is sharply
changed. However, when the specifications of the rotary
machine and the control device vary from specifications
assumed in advance, the flux weakening current might become
excessive or deficient. In a steady state in which there is10
no sharp change in the rotational speed and currents flowing
through the windings can almost follow the current commands,
combining a method of performing feedback of the steady state
enables selection of optimum flux weakening current. The
second flux weakening current calculation unit 814 is15
provided for calculating the flux weakening current in the
steady state.
[0083] The final flux weakening current determination unit
815 receives the first flux weakening current calculated by
the first flux weakening current calculation unit 812, the20
second flux weakening current calculated by the second flux
weakening current calculation unit 814, and the field winding
current command and the field winding current which are not
shown. The final flux weakening current determination unit
815 determines final flux weakening current by selecting one25
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of the first flux weakening current inputted from the first
flux weakening current calculation unit 812 and the second
flux weakening current inputted from the second flux
weakening current calculation unit 814, or determines the
final flux weakening current by calculating a weighted5
average value of both currents. Then, the final flux
weakening current determination unit 815 outputs the
determined final flux weakening current to the final current
command calculation unit 813.
[0084] In the stator winding current command and the field10
winding current command calculated by the current command
calculation unit 810, normally, voltage saturation has been
taken into consideration. However, in a case where the field
winding current is significantly greater than the field
winding current command, the d-axis magnetic flux φd in15
Formula (1) becomes greater than assumed, so that it becomes
difficult for the stator winding current to follow the stator
winding current command due to voltage saturation. In such a
case, in order to stabilize current control, it is necessary
to ensure the final flux weakening current quickly so as to20
suppress voltage saturation. That is, in a case where the
field winding current is significantly greater than the field
winding current command, it is necessary to select the first
flux weakening current calculated by the first flux weakening
current calculation unit 812. Specifically, when the field25
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winding current command is sharply decreased in the converter
as shown in FIG. 4, the above state is likely to occur.
[0085] On the other hand, in a steady state in which there
is no sharp change in the rotational speed and currents
flowing through the windings can almost follow the current5
commands, fast response is not required, and therefore
selecting the second flux weakening current calculated by the
second flux weakening current calculation unit can optimize
the stator winding current, whereby efficient operation can
be achieved.10
[0086] In the control device for the rotary machine
according to the present embodiment, the current command
generation unit 81 includes the second flux weakening current
calculation unit 814 and the final flux weakening current
determination unit 815. Therefore, in the control device for15
the rotary machine according to the present embodiment, in a
case where the field winding current is significantly greater
than the field winding current command, the first flux
weakening current calculated by the first flux weakening
current calculation unit can be selected, and otherwise, the20
second flux weakening current calculated by the second flux
weakening current calculation unit can be selected. As a
result, the control device for the rotary machine according
to the present embodiment can perform optimum current control
in which variation in the specifications of the rotary25
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machine and the control device is taken into consideration,
in a steady state, and can quickly eliminate voltage
saturation even when the rotational speed sharply changes.
[0087] The final flux weakening current determination unit
815 calculates a deviation between the field winding current5
and the field winding current command, and sets, for the
deviation, a first threshold and a second threshold greater
than the first threshold. Then, when the deviation between
the field winding current and the field winding current
command is smaller than the first threshold, the final flux10
weakening current determination unit 815 determines the
second flux weakening current calculated by the second flux
weakening current calculation unit 814, as final flux
weakening current. When the deviation between the field
winding current and the field winding current command is15
greater than the second threshold, the final flux weakening
current determination unit 815 determines the first flux
weakening current calculated by the first flux weakening
current calculation unit 812, as final flux weakening
current. When the deviation between the field winding20
current and the field winding current command is not smaller
than the first threshold and not greater than the second
threshold, the final flux weakening current determination
unit 815 determines the weighted average of the first flux
weakening current inputted from the first flux weakening25
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current calculation unit 812 and the second flux weakening
current inputted from the second flux weakening current
calculation unit 814, as final flux weakening current.
[0088] Although the disclosure is described above in terms
of various exemplary embodiments and implementations, it5
should be understood that the various features, aspects, and
functionality described in one or more of the individual
embodiments are not limited in their applicability to the
particular embodiment with which they are described, but
instead can be applied, alone or in various combinations to10
one or more of the embodiments of the disclosure.
It is therefore understood that numerous
modifications which have not been exemplified can be devised
without departing from the scope of the present disclosure.
For example, at least one of the constituent components may15
be modified, added, or eliminated. At least one of the
constituent components mentioned in at least one of the
preferred embodiments may be selected and combined with the
constituent components mentioned in another preferred
embodiment.20
DESCRIPTION OF THE REFERENCE CHARACTERS
[0089] 1 control device
2 rotary machine
3 DC power supply25
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4 stator winding power conversion unit
5 field winding power conversion unit
6 stator winding current detection unit
7 field winding current detection unit
8 processor5
9 storage device
81 current command generation unit
82 stator winding voltage command unit
83 stator winding switching command generation
unit10
84 field winding voltage command unit
85 field winding switching command generation unit
810 current command calculation unit
811 allowable magnetic flux calculation unit
812 first flux weakening current calculation unit15
813 final current command calculation unit
814 second flux weakening current calculation unit
815 final flux weakening current determination
unit
20
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We Claim :
[Claim 1] A control device for a rotary machine including a
rotor having a field winding and a stator having a stator
winding, the control device comprising:
a current command generation unit which generates a5
field winding current command for field winding current and a
stator winding current command for stator winding current, on
the basis of an operation command inputted from outside;
a field winding voltage command unit which
generates a field winding voltage command for voltage to be10
applied to the field winding, on the basis of the field
winding current command;
a stator winding voltage command unit which
generates a stator winding voltage command for voltage to be
applied to the stator winding, on the basis of the stator15
winding current command;
a field winding power conversion unit which applies
voltage to the field winding on the basis of the field
winding voltage command; and
a stator winding power conversion unit which20
applies voltage to the stator winding on the basis of the
stator winding voltage command, wherein
the current command generation unit includes
a current command calculation unit which
calculates the field winding current command and the stator25
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winding current command on the basis of the operation command
and DC voltage inputted from outside,
an allowable magnetic flux calculation unit
which calculates an allowable magnetic flux which is an
allowable value of a magnetic flux interlinking the stator5
winding, on the basis of a rotational speed of the rotary
machine, the DC voltage, the stator winding current command,
and the field winding current,
a first flux weakening current calculation unit
which calculates first flux weakening current on the basis of10
the field winding current, the stator winding current
command, and the allowable magnetic flux, and
a final current command calculation unit which
calculates the stator winding current command that is final,
on the basis of the stator winding current command and the15
first flux weakening current.
[Claim 2] The control device for the rotary machine according
to claim 1, wherein
the allowable magnetic flux calculation unit20
calculates the allowable magnetic flux on the basis of a d-
axis current lower limit value determined by the field
winding current.
[Claim 3] The control device for the rotary machine according25
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to claim 1, wherein
the allowable magnetic flux calculation unit
calculates the allowable magnetic flux on the basis of a
torque command included in the operation command.
5
[Claim 4] The control device for the rotary machine according
to claim 2 or 3, wherein
the allowable magnetic flux calculated by the
allowable magnetic flux calculation unit is a d-axis
component.10
[Claim 5] The control device for the rotary machine according
to any one of claims 1 to 4, wherein
the first flux weakening current calculation unit
calculates a d-axis component of the first flux weakening15
current on the basis of the field winding current, a q-axis
component of the stator winding current command, and a d-axis
component of the allowable magnetic flux.
[Claim 6] The control device for the rotary machine according20
to any one of claims 1 to 4, wherein
the first flux weakening current calculation unit
calculates a q-axis component of the first flux weakening
current on the basis of the field winding current, a d-axis
current lower limit value, and a q-axis component of the25
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allowable magnetic flux.
[Claim 7] The control device for the rotary machine according
to any one of claims 1 to 4, wherein
the first flux weakening current calculation unit5
calculates a d-axis component of the first flux weakening
current on the basis of the field winding current, a q-axis
component of the stator winding current command, and a d-axis
component of the allowable magnetic flux, and calculates a q-
axis component of the first flux weakening current on the10
basis of the field winding current, the first flux weakening
current, and a q-axis component of the allowable magnetic
flux.
[Claim 8] The control device for the rotary machine according15
to any one of claims 1 to 7, further comprising:
a second flux weakening current calculation unit
which calculates second flux weakening current on the basis
of application voltage to the stator winding; and
a final flux weakening current determination unit20
which determines one of the first flux weakening current and
the second flux weakening current, as final flux weakening
current, on the basis of a deviation between the field
winding current and the field winding current command, or
determines a weighted average of the first flux weakening25
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current and the second flux weakening current, as final flux
weakening current, on the basis of a deviation between the
field winding current and the field winding current command,
wherein
the final current command calculation unit5
calculates the stator winding current command that is final,
on the basis of the final flux weakening current and the
stator winding current command determined by the final flux
weakening current determination unit.
10
[Claim 9] The control device for the rotary machine according
to claim 8, wherein
the final flux weakening current determination unit
calculates the deviation between the field winding current
and the field winding current command, and sets, for the15
deviation, a first threshold and a second threshold greater
than the first threshold,
when the deviation is smaller than the first
threshold, the final flux weakening current determination
unit determines the second flux weakening current as the20
final flux weakening current,
when the deviation is greater than the second
threshold, the final flux weakening current determination
unit determines the first flux weakening current as the final
flux weakening current, and25
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when the deviation is not smaller than the first
threshold and not greater than the second threshold, the
final flux weakening current determination unit determines
the weighted average of the first flux weakening current and
the second flux weakening current, as the final flux5
weakening current.