Technical Field
[0001]
The present invention relates to a synchronous
machine control device and a synchronous machine control
method for driving a synchronous machine such as a
synchronous motor, and an electric vehicle using the same.
Background Art
[0002]
In order to reduce the size of a synchronous motor,
high-speed rotation and high magnetic flux density of the
motor have been advanced. In particular, in an electric
vehicle such as an electric automobile, since the weight of
the motor has an influence on the power consumption amount,
such a tendency is remarkable.
[0003]
As a conventional control technique corresponding to
high-speed rotation, a control technique disclosed in PTL 1
is known.
[0004]
In the control technique disclosed in PTL 1, a second
3
current command value is created such that a current
detection value for a d-axis current and a q-axis current
approaches a first current command value. Then, a voltage
command value is created based on the second current
command value.
[0005]
In addition, as a conventional control technique
corresponding to high magnetic flux density, control
techniques disclosed in PTLs 2 and 3 are known.
[0006]
In the control technique disclosed in PTL 2, a
voltage command value is created based on the second
current command value in PTL 1 and based on a coil
interlinkage magnetic flux.
[0007]
In the control technique disclosed in PTL 3, a
current control gain is similarly changed in response to a
change in an inductance value with respect to a motor
current value.
Citation List
Patent Literature
[0008]
PTL 1: JP 2004-297966 A
PTL 2: International Publication No. 2010/116815
PTL 3: JP 2003-348875 A
4
Summary of Invention
Technical Problem
[0009]
When the control technique is applied to achieve both
high-speed rotation and high magnetic flux density of the
motor, the control system becomes complicated. In
particular, the number of constants used for a magnetic
flux-related computation increases, and thus parameter
identification has difficulty, or the load on a control
device increases. For this reason, it is difficult to
perform mounting on an application target such as an
electric vehicle.
[0010]
Therefore, the present invention provides a
synchronous machine control device and a synchronous
machine control method capable of improving performance of
a motor without complicating a control system, and an
electric vehicle using the same.
Solution to Problem
[0011]
In order to solve the above problems, according to
the present invention, a synchronous machine control device
controls a power converter that supplies electric power to
5
a synchronous machine. The synchronous machine control
device includes a first magnetic flux command computation
unit that computes a first magnetic flux command value from
a current command value of the synchronous machine, a
magnetic flux estimation unit that estimates a magnetic
flux value of the synchronous machine from a current
detection value of the synchronous machine, and a voltage
computation unit that creates a voltage command value of
the power converter such that the first magnetic flux
command value coincides with the magnetic flux value.
[0012]
In order to solve the above problems, according to
the present invention, there is provided a synchronous
machine control method of controlling a power converter
that supplies electric power to a synchronous machine. The
synchronous machine control method includes computing a
first magnetic flux command value from a current command
value of the synchronous machine, estimating a magnetic
flux value of the synchronous machine from a current
detection value of the synchronous machine, and creating a
voltage command value of the power converter such that the
first magnetic flux command value coincides with the
magnetic flux value.
[0013]
In order to solve the above problems, according to
6
the present invention, an electric vehicle includes a wheel,
a synchronous machine that drives the wheel, a power
converter that supplies electric power to the synchronous
machine, and a control device that controls the power
converter. The control device is the synchronous machine
control device according to the present invention.
Advantageous Effects of Invention
[0014]
According to the present invention, it is possible to
accurately control a synchronous machine in consideration
of an influence of magnetic saturation of the synchronous
machine without complicating a control system.
[0015]
Objects, configurations, and advantageous effects
other than those described above will be clarified by the
descriptions of the following embodiments.
Brief Description of Drawings
[0016]
[FIG. 1] FIG. 1 is a block diagram illustrating a
functional configuration of a synchronous machine control
device according to a first embodiment.
[FIG. 2] FIG. 2 is a block diagram illustrating a
functional configuration of a PI controller in a second dq-
7
axis magnetic flux command computation unit 25.
[FIG. 3] FIG. 3 illustrates a configuration of a
voltage vector computation unit 19 configured based on an
inverse model represented by Expression (1).
[FIG. 4] FIG. 4 illustrates an example of a
relationship between a magnetic flux and a current.
[FIG. 5] FIG. 5 is a block diagram illustrating a
functional configuration of a synchronous machine control
device according to a second embodiment.
[FIG. 6] FIG. 6 is a block diagram illustrating an
example of a functional configuration of a non-interference
control computation unit 13.
[FIG. 7] FIG. 7 is a block diagram illustrating a
functional configuration of a synchronous machine control
device according to a third embodiment.
[FIG. 8] FIG. 8 is a block diagram illustrating an
example of a functional configuration of a second dq-axis
magnetic flux command computation unit 25B.
[FIG. 9] FIG. 9 is a block diagram illustrating a
configuration of an electric vehicle according to a fourth
embodiment.
Description of Embodiments
[0017]
Hereinafter, an embodiment of the present invention
8
will be described according to first to fourth embodiments
below with reference to the drawings. In the drawings, the
same reference signs indicate the same configuration
requirements or configuration requirements having similar
functions.
[0018]
In the first to fourth embodiments, a synchronous
machine being a control target is a permanent magnet
synchronous motor (referred to as a “PMSM” (abbreviation of
Permanent Magnet Synchronous Motor)).
First embodiment
[0019]
FIG. 1 is a block diagram illustrating a functional
configuration of a synchronous machine control device
according to a first embodiment. In the present embodiment,
a computer system such as a microcomputer executes a
predetermined program to function as the synchronous
machine control device illustrated in FIG. 1 (the same
applies to other embodiments).
[0020]
In FIG. 1, a power converter 2 converts DC power from
a DC voltage source 9 (for example, a battery) into AC
power and outputs the AC power to a PMSM 1. The PMSM 1 is
rotationally driven by the AC power. The power converter 2
includes an inverter main circuit including a semiconductor
9
switching element. The semiconductor switching element is
controlled to be turned on or off by a gate signal, thereby
the DC power is converted into the AC power. As the
semiconductor switching element, for example, an insulated
gate bipolar transistor (IGBT) is applied.
[0021]
A phase current detector 3 detects a three-phase
motor current flowing from the power converter 2 into the
PMSM 1, that is, a U-phase current Iu, a V-phase current Iv,
and a W-phase current Iw. Then, the phase current detector
3 outputs the U-phase current Iu, the V-phase current Iv,
and the W-phase current Iw as a U-phase current detection
value Iuc, a V-phase current detection value Ivc, and a Wphase current detection value Iwc, respectively. As the
phase current detector 3, a Hall current transformer (CT)
or the like is applied.
[0022]
A magnetic pole position detector 4 detects the
magnetic pole position of the PMSM 1 and outputs magnetic
pole position information θ*. A resolver or the like is
applied as the magnetic pole position detector 4.
[0023]
A frequency computation unit 5 computes speed
information ω1* from the magnetic pole position information
θ* output by the magnetic pole position detector 4, by time
10
differentiation computation or the like, and outputs the
speed information ω1*.
[0024]
A coordinate transformation unit 7 transforms Iuc,
Ivc, and Iwc output by the phase current detector into dqaxis current detection values Idc and Iqc in a rotating
coordinate system in accordance with the magnetic pole
position information θ*, and outputs Idc and Iqc.
[0025]
A dq-axis magnetic flux estimation unit 23 estimates
dq-axis magnetic flux estimation values φdc and φqc based
on the dq-axis current detection values Idc and Iqc output
by the coordinate transformation unit 7, with reference to
a lookup table (table data). The lookup table (table data)
used as the reference by the dq-axis magnetic flux
estimation unit 23 is table data representing the
correspondence between Idc and Iqc, and φdc and φqc. Such
a lookup table is stored in a storage device (not
illustrated) provided in the synchronous machine control
device in the present embodiment. A predetermined function
(such as an approximate expression) may be used instead of
the lookup table.
[0026]
A first dq-axis magnetic flux command computation
unit 21 computes and outputs first dq-axis magnetic flux
11
command values φd* and φq* based on dq-axis current command
values Idc* and Iqc* given from a higher control device or
the like, with reference to a lookup table (table data).
The lookup table (table data) used as the reference by the
first dq-axis magnetic flux command computation unit 21 is
table data representing the correspondence between Idc* and
Iqc*, and φd* and φq*. Such a lookup table is stored in a
storage device (not illustrated) provided in the
synchronous machine control device in the present
embodiment. A predetermined function (such as an
approximate expression) may be used instead of the lookup
table.
[0027]
A second dq-axis magnetic flux command computation
unit 25 computes second dq-axis magnetic flux command
values φd** and φq** by a proportional integral (PI)
controller such that the first dq-axis magnetic flux
command values φd* and φq* coincide with the dq-axis
magnetic flux estimation values φdc and φqc. Then, the
second dq-axis magnetic flux command computation unit 25
outputs the computed second dq-axis magnetic flux command
values φd** and φq**.
[0028]
FIG. 2 is a block diagram illustrating a functional
configuration of the PI controller in the second dq-axis
12
magnetic flux command computation unit 25.
[0029]
As illustrated in the upper diagram of FIG. 2, in the
PI controller that computes the second d-axis magnetic flux
command value φd**, an adder-subtractor 81 computes a
difference (φd* − φdc) between the first d-axis magnetic
flux command value φd* and the d-axis magnetic flux
estimation value φdc, and multiplies the difference
computation value by a proportional gain 87 (KP). An
integrator 83 integrates the difference computation value
is integrated, and the integrated value is multiplied by an
integral gain 85 (KI). An adder 89 adds the difference
computation value multiplied by the proportional gain 87
and the integrated value multiplied by the integral gain 85
to compute the second d-axis magnetic flux command value
φd**.
[0030]
As illustrated in the lower diagram of FIG. 2, in the
PI controller that computes the second q-axis magnetic flux
command value φq**, an adder-subtractor 91 computes a
difference (φq* − φqc) between the first q-axis magnetic
flux command value φq* and the q-axis magnetic flux
estimation value φqc, and multiplies the difference
computation value by a proportional gain 97 (KP). An
integrator 93 integrates the difference computation value
13
is integrated, and the integrated value is multiplied by an
integral gain 95 (KI). An adder 99 adds the difference
computation value multiplied by the proportional gain 97
and the integrated value multiplied by the integral gain 95
to compute the second q-axis magnetic flux command value
φq**.
[0031]
A voltage vector computation unit 19 illustrated in
FIG. 1 creates a voltage command value by an inverse model
of a motor model.
[0032]
The inverse model of the motor model is represented
by, for example, a voltage equation as in Expression (1),
where a d-axis magnetic flux and a q-axis magnetic flux of
a motor are set as φd and φq, respectively, a d-axis
voltage and a q-axis voltage of the motor are set as Vd and
Vq, respectively, and the motor speed is set as ω1.
[0033]
[Math. 1]
[0034]
In the present embodiment, the inverse model
14
represented by Expression (1) is applied, where Vd and Vq
are respectively set as a d-axis voltage command value Vd*
and a q-axis voltage command value Vq*, φd and φq are
respectively set as a second d-axis magnetic flux command
value φd** and a second q-axis magnetic flux command value
φq**, and ω1 is set as speed information ω1*.
[0035]
As will be described later, in Expression (1),
magnetic saturation of the motor is considered.
[0036]
FIG. 3 illustrates a configuration of the voltage
vector computation unit 19 configured based on the inverse
model represented by Expression (1). R, Ld, Lq, and Ke
indicate a winding resistance, a d-axis inductance, a qaxis inductance, and a magnet magnetic flux in the PMSM 1,
respectively.
[0037]
As illustrated in FIG. 3, differentiation of φd** is
computed by a differentiator 45. In addition, an addersubtractor 44 computes a difference (φd**- Ke) between φd**
and Ke. The difference computation value is multiplied by
R/Ld (46). An adder 47 adds the differential computation
value by the differentiator 45 and the difference
computation value multiplied by the gain R/Ld (46). In
addition, a multiplier 48 multiplies ω1* and φq**.
15
Furthermore, the adder-subtractor 49 computes a difference
between the addition computation value by the adder 47 and
the multiplication value by the multiplier 48 to create Vd*.
[0038]
As illustrated in FIG. 3, the differentiator 35
computes the differentiation of φq**. Further, φq* * is
multiplied by R/Lq (36). The differential computation
value by a differentiator 35 and φq** multiplied by R/Lq
(36) are added by an adder 37. In addition, ω1* and φd**
are multiplied by a multiplier 38. Furthermore, an adder
39 adds the addition computation value by the adder 37 and
the multiplication value by the multiplier 38 to create Vq*.
[0039]
As described above, the voltage vector computation
unit can be configured based on the voltage equation
representing the inverse model of the motor model.
[0040]
The coordinate transformation unit 11 illustrated in
FIG. 1 performs coordinate transformation on the dq-axis
voltage command values Vd* and Vq* for the power converter
2, which are output from the voltage vector computation
unit 19, by using the magnetic pole position information θ*
detected by the magnetic pole position detector 4, thereby
creating and outputting three-phase voltage command values
Vu*, Vv*, and Vw* for the power converter 2.
16
[0041]
A DC voltage detector 6 detects the voltage of the DC
voltage source 9 and outputs DC voltage information Vdc.
[0042]
A PWM controller 12 receives the three-phase voltage
command values Vu*, Vv*, and Vw* from the voltage vector
computation unit 19, and receives the DC voltage
information Vdc from the DC voltage detector 6. Then, the
PWM controller 12 creates and outputs a gate signal to be
given to the power converter 2 based on the received threephase voltage command values Vu*, Vv*, and Vw* and DC
voltage information Vdc, by pulse width modulation. For
example, the PWM controller 12 creates a gate signal by
pulse width modulation using a triangular wave as a carrier
signal and using the three-phase voltage command values as
a modulation wave.
[0043]
Means for creating the voltage command value in
consideration of magnetic saturation of the PMSM 1 used in
the voltage vector computation unit 19 in the present
embodiment will be described below.
[0044]
First, in a case where currents (dq-axis currents Id
and Iq) are used as a state quantity, the voltage equation
is represented as Expression (2) in consideration of
17
magnetic saturation.
[0045]
[Math. 2]
[0046]
Here, Ldh, Lqh, Ldqh, and Lqdh represent dynamic
inductances, and Ld, Lq, Ldq, and Lqd represent static
inductances. The above inductances will be described with
reference to FIG. 4.
[0047]
FIG. 4 illustrates an example of a relationship
between the magnetic flux and the current. The vertical
axis and the horizontal axis respectively indicate an
example of a relationship between the magnetic flux and the
current (solid line in the drawing).
[0048]
As illustrated in FIG. 4, due to the influence of
magnetic saturation, as the q-axis current (Iq) increases,
the degree of increase in the q-axis magnetic flux (φq)
becomes gentler. Therefore, as the inductance, the dynamic
inductance and the static inductance are defined as follows.
The dynamic inductance Lqh refers to an inclination
(dφq/dt) of a tangent line (broken line in the drawing) at
18
a certain operating point (Iq, φq). The static inductance
Lq refers to an inclination (φq/Iq) of a straight line
(broken line in the drawing) connecting the operating point
and a point at which the q-axis current (Iq) is 0.
[0049]
Although not illustrated, the relationship between
the d-axis magnetic flux and the d-axis current, the
dynamic inductance Ldh, and the static inductance Ld are
similar to those in FIG. 4.
[0050]
In Expression (2), the coefficient (matrix) in the
current derivative term (second term on the right side) is
the dynamic inductance, and the coefficient (matrix) in the
induced voltage term (third term on the right side) is the
static inductance.
[0051]
In addition, in a case where magnetic saturation is
remarkable, mutual interference between control axes, that
is, between dq axes occurs. Such mutual interference is
represented by the dynamic inductances Ldqh and Lqdh in the
coefficient (matrix) of the current derivative term and the
static inductances Ldq and Lqd in the coefficient (matrix)
of the induced voltage term.
[0052]
In a case where the PMSM 1 is controlled based on
19
Expression (2), that is, in consideration of magnetic
saturation using the current as the state quantity, eight
types of inductances (Ldh, Lqh, Ldqh, Lqdh, Ld, Lq, Ldq,
and Lqd) as described above are used. Thus, in this case,
the synchronous machine control device includes eight
pieces of table data or functions (such as an approximate
expression) representing the correspondence between each
inductance value and the current value (d-axis current
value and q-axis current value).
[0053]
Considering the temperature dependency of the
inductances, each piece of the table data or each
mathematical expression (such as an approximate expression)
is table data or a function of three variables by using the
d-axis current value, the q-axis current value, and the
temperature as variables.
[0054]
Furthermore, since the magnet magnetic flux Ke in
Expression (2) has dependency on the q-axis current Iq and
the temperature T, the synchronous machine control device
includes one piece of table data or function (such as an
approximate expression) of two variables representing the
relationship between the two variables and Ke by using Iq
and T as variables.
[0055]
20
As described above, in a case where the PMSM 1 is
controlled in consideration of magnetic saturation by using
the current as the state quantity, the synchronous machine
control device includes a plurality of pieces of
multivariable table data or multivariable functions.
[0056]
Therefore, as described below, in the present
embodiment, by using the magnetic flux as the state
quantity as in the inverse model of the motor model
represented by Expression (1) described above, the total
number (nine in a case of using the current as the state
quantity as described above) of pieces of table data or
functions (such as an approximate expression) used in the
synchronous machine control device is reduced even while
considering magnetic saturation.
[0057]
In a case where the magnetic flux (dq-axis magnetic
flux φd, φq) are used as the state quantity, the voltage
equation is represented as Expression (3) in consideration
of magnetic saturation.
[0058]
[Math. 3]
21
[0059]
In many high-efficiency PMSMs, for example, for
automobiles, the winding resistance R is sufficiently small.
Thus, the influence of the first term of Expression (3) in
motor control is relatively small. Therefore, even though
Ld, Lq, and Ke are set as constant values by approximation
as in Expression (1), the influence on the motor control is
small. Therefore, the voltage vector computation unit 19
according to the present embodiment sets Ld, Lq, and Ke in
Expression (1) as constant values based on Expression (1)
described above in which the magnetic flux is set as the
state quantity. Then, the voltage vector computation unit
19 creates the dq-axis voltage command values (Vd* and Vq*)
in accordance with the dq-axis magnetic flux command values
(φd** and φq**).
[0060]
In this case, the synchronous machine controller
device includes table data or a function (such as an
approximate expression) indicating the correspondence
relationship between each of the d-axis magnetic flux (φd)
and the q-axis magnetic flux (φq), and the current (d-axis
current Id, q-axis current Iq). Therefore, the synchronous
machine control device includes a total of two pieces of
table data or functions.
[0061]
22
As described above, by setting the magnetic flux as
the state quantity, the number of pieces of table data or
functions used for motor control is reduced. As a result,
since the control system is simplified while considering
magnetic saturation, it is possible to reduce the
computation load of the synchronous machine control device
and to shorten the parameter identification time.
[0062]
In the present embodiment, the dq-axis voltage
command values Vd* and Vq* are created based on the second
dq-axis magnetic flux command values φd** and φq** created
by the second dq-axis magnetic flux command computation
unit 25, by using the inverse model of the motor model.
Therefore, even in a high-speed region, it is possible to
cause the d-axis magnetic flux estimation value φdc and the
q-axis magnetic flux estimation value φqc to accurately
coincide with the second d-axis magnetic flux command value
φd** and the second q-axis magnetic flux command value φq**,
respectively. Thus, according to the synchronous machine
control device in the present embodiment, it is possible to
control the high-speed rotation of the PMSM 1.
[0063]
In the present embodiment, the influence of the
temperature dependency of the magnetic flux is alleviated
by the PI controller or an I controller provided in the
23
second dq-axis magnetic flux command computation unit 25.
Therefore, the table data or the function used for the
computation of the magnetic flux (φd, φq) may be table data
or a function (such as an approximate expression) in which
the temperature is not included as a variable and only the
current is used as a variable. As a result, it is possible
to reduce the computation load of the synchronous machine
control device and to shorten the parameter identification
time.
[0064]
In addition, because the same table data or function
are used by the first dq-axis magnetic flux command
computation unit 21 and the dq-axis magnetic flux
estimation unit 23, Idc and Iqc are controlled to coincide
with Id* and Iq*, respectively, through the magnetic flux.
In this case, a current control system is substantially
configured.
[0065]
In addition, since each of the first dq-axis magnetic
flux command computation unit 21 and the dq-axis magnetic
flux estimation unit 23 uses independent table data or
function, it is possible to perform control in
consideration of mutual interference between the axes. In
this case, each of the first dq-axis magnetic flux command
computation unit 21 and the dq-axis magnetic flux
24
estimation unit 23 uses table data or a function
representing the correspondence relationship between the
dq-axis magnetic flux command value (φd*, φq*) and the dqaxis current command value (Id*, Iq*), and uses table data
or a function representing the correspondence relationship
between the dq-axis magnetic flux estimation value (φdc,
φqc) and the dq-axis current detection value (Idc, Iqc).
[0066]
Since the synchronous machine control device in the
present embodiment substantially considers the dynamic
inductance and the static inductance of the motor, the
synchronous machine control device is suitable for
application to an electric vehicle such as an electric
automobile in which a PMSM having a large influence of
magnetic saturation is used and an accurate torque response
is required.
[0067]
The above-described lookup table, table data, and
function (approximate expression), which are information
indicating the correspondence relationship between the
magnetic flux and the current in the PMSM 1, can be set
based on actual measurement, magnetic field analysis, or
the like.
Second embodiment
[0068]
25
FIG. 5 is a block diagram illustrating a functional
configuration of a synchronous machine control device
according to a second embodiment of the present invention.
[0069]
Differences from the first embodiment will be mainly
described below.
[0070]
A dq-axis magnetic flux command computation unit 20
has the similar function to the first dq-axis magnetic flux
command computation unit 21 (FIG. 1) described above. That
is, the dq-axis magnetic flux command computation unit 20
computes and outputs the dq-axis magnetic flux command
values φd* and φq* based on the dq-axis current command
values Id* and Iq* given from a higher control device or
the like, by using table data or a function (such as an
approximate expression), as in the first embodiment.
[0071]
A dq-axis voltage command computation unit 15
computes and outputs a d-axis voltage provisional command
value VdPI* by a controller such as a proportional integral
(PI) machine such that the d-axis magnetic flux command
value φd* coincides with the d-axis magnetic flux
estimation value φdc. In addition, the dq-axis voltage
command computation unit 15 computes and outputs a d-axis
voltage provisional command value VqPI* by a controller
26
such as a proportional integral (PI) machine such that the
q-axis magnetic flux command value φq* coincides with the
q-axis magnetic flux estimation value φqc.
[0072]
A non-interference control computation unit 13
creates and outputs dq-axis voltage command values VdFF*
and VqFF* for inter-axis non-interference control, based on
the dq-axis voltage command values φd* and φq* and the
speed information ω1*.
[0073]
FIG. 6 is a block diagram illustrating an example of
a functional configuration of the non-interference control
computation unit 13.
[0074]
As illustrated in FIG. 6, φd* is input to a primary
delay computing machine 51 in which the reciprocal of the
cutoff frequency ωc of the current control system is set as
a time constant. A multiplier 55 multiplies the output of
the primary delay computing machine 51, that is, the result
obtained by performing the primary delay computation on φd*
by ω1*, and thus the d-axis voltage command value VdFF* for
the inter-axis non-interference control is created.
[0075]
As illustrated in FIG. 6, φq* is input to a primary
delay computing machine 53 similar to the primary delay
27
computing machine 51. A multiplier 57 multiplies the
output of the primary delay computing machine 53, that is,
the result obtained by performing the primary delay
computation on φq* by ω1*. The positive sign and the
negative sign of the output of the multiplier 57 are
inverted by an inverter 59 (or gain “-1”), and thus the qaxis voltage command value VqFF* for inter-axis noninterference control is created.
[0076]
In FIG. 5, a voltage vector addition unit 10 creates
a d-axis voltage command value Vd* by adding VdPI* and VdFF*,
and outputs the d-axis voltage command value Vd*. The
voltage vector addition unit 10 adds VqPI* and VqFF* and
outputs a q-axis voltage command value Vq*.
[0077]
In the second embodiment, the dq-axis magnetic flux
command values used for computation of the induced voltage
term (third term on the right side of Expressions (1) and
(3)) corresponds to the result obtained by performing the
primary delay computation on the first dq-axis magnetic
flux command values (φd* and φq* illustrated in FIG. 1) in
the first embodiment. Therefore, according to the
synchronous machine control device in the second embodiment,
similar to the first embodiment, the dynamic inductance and
the static inductance are considered, and the influence of
28
the mutual interference between the axes is suppressed.
Thus, it is possible to control the PMSM in which the
magnetic flux saturation occurs, with high accuracy.
Third embodiment
[0078]
FIG. 7 is a block diagram illustrating a functional
configuration of a synchronous machine control device
according to a third embodiment of the present invention.
[0079]
Differences from the first embodiment will be mainly
described below.
[0080]
In the present embodiment, the configuration of a
second dq-axis magnetic flux command computation unit 25B
illustrated in FIG. 7 is different from that in the first
embodiment (FIG. 2) and includes a primary delay computing
machine. Other components are similar to those in the
first embodiment (FIG. 1).
[0081]
FIG. 8 is a block diagram illustrating an example of
a functional configuration of the second dq-axis magnetic
flux command computation unit 25B.
[0082]
As illustrated in FIG. 8, in the second dq-axis
magnetic flux command computation unit 25B, primary delay
29
computing machines (84 and 94) in which the reciprocal of
the cutoff frequency ωc of the current control system is
set as a time constant are added to the proportional
integral (PI) controller illustrated in FIG. 2.
[0083]
The first dq magnetic flux command value (φd*, φq*)
is input to the primary delay computing machine (84, 94).
An adder (88, 98) adds, to the output of a primary delay
computing machine 51, that is, the result obtained by
performing the primary delay computation on φd* and φq*,
the difference computation value obtained by multiplying
the proportional gain (87, 97) and the integrated value
obtained by multiplying the integral gain (85, 95)
described above. In this manner, the second dq-axis
magnetic flux command value (φd**, φd**) is created.
[0084]
The synchronous machine control device according to
the third embodiment includes a magnetic flux feedforward
control system by a primary delay controller, in addition
to a magnetic flux feedback control system by a
differential integration controller. This improves control
responsiveness.
Fourth embodiment
[0085]
FIG. 9 is a block diagram illustrating a
30
configuration of an electric vehicle according to a fourth
embodiment of the present invention. An electric vehicle
in the present embodiment is an electric automobile.
[0086]
A motor control device 100 controls AC power supplied
from the power converter 2 (inverter) to the PMSM 1. The
DC voltage source 9 (for example, a battery) supplies DC
power to the power converter 2 (inverter). The power
converter 2 (inverter) is controlled by the motor control
device 100 to convert DC power from the DC voltage source 9
into AC power. As the motor control device 100, any one of
the synchronous machine control devices in the first to
third embodiments described above is applied.
[0087]
The PMSM 1 is mechanically connected to a
transmission 101. The transmission 101 is mechanically
connected to a drive shaft 105 via a differential gear 103
and supplies mechanical power to a wheel 107. As a result,
the wheel 107 is rotationally driven.
[0088]
The PMSM 1 may be directly connected to the
differential gear 103 without the transmission 101. Each
of the front and rear wheels of the automobile may be
driven by an independent PMSM and inverter.
[0089]
31
According to the fourth embodiment, the synchronous
machine control device according to any one of the first to
third embodiments described above is applied as the motor
control device 100. Thus, it is possible to control the
PMSM having a large influence of magnetic saturation, with
high accuracy. Therefore, the accuracy of the driving
control of the electric automobile driven by the PMSM is
improved. Thus, the ride comfort for the passenger of the
electric automobile is improved.

WE CLAIM:
[Claim 1]
A synchronous machine control device that controls a
power converter that supplies electric power to a
synchronous machine, the synchronous machine control device
comprising:
a first magnetic flux command computation unit that
computes a first magnetic flux command value from a current
command value of the synchronous machine;
a magnetic flux estimation unit that estimates a
magnetic flux value of the synchronous machine from a
current detection value of the synchronous machine; and
a voltage computation unit that creates a voltage
command value of the power converter such that the first
magnetic flux command value coincides with the magnetic
flux value.
[Claim 2]
The synchronous machine control device according to
claim 1, wherein
the first magnetic flux command computation unit
computes the first magnetic flux command value based on
information indicating a correspondence relationship
between the current command value and the first magnetic
flux command value, and
the magnetic flux estimation unit estimates the
37
magnetic flux value based on information indicating a
correspondence relationship between the current detection
value and the magnetic flux value.
[Claim 3]
The synchronous machine control device according to
claim 2, wherein the information indicating the
correspondence relationship between the current command
value and the first magnetic flux command value is the same
as the information indicating the correspondence
relationship between the current detection value and the
magnetic flux value.
[Claim 4]
The synchronous machine control device according to
claim 1, further comprising:
a second magnetic flux command computation unit that
computes a second magnetic flux command value such that the
first magnetic flux command value coincides with the
magnetic flux value,
wherein the voltage computation unit creates the
voltage command value based on the second magnetic flux
command value and a speed of the synchronous machine.
[Claim 5]
The synchronous machine control device according to
claim 4, wherein the second magnetic flux command
computation unit computes the second magnetic flux command
38
value by using a proportional controller and an integral
controller.
[Claim 6]
The synchronous machine control device according to
claim 4, wherein the voltage computation unit computes the
second magnetic flux command value by using a proportional
controller, an integral controller, and a primary delay
controller constituting a feedforward control system.
[Claim 7]
The synchronous machine control device according to
claim 6, wherein the primary delay controller sets a
reciprocal of a cutoff frequency in a current control
system as a time constant.
[Claim 8]
The synchronous machine control device according to
claim 4, wherein the voltage computation unit is configured
by an inverse model of the synchronous machine.
[Claim 9]
The synchronous machine control device according to
claim 1, further comprising:
a first voltage command computation unit that creates
a first voltage command value such that the first magnetic
flux command value coincides with the magnetic flux value;
and
a second voltage command computation unit that
39
creates a second voltage command for non-interference
control, based on the first magnetic flux command value and
a speed of the synchronous machine,
wherein the voltage computation unit creates the
voltage command value of the power converter based on the
first voltage command value and the second voltage command
value.
[Claim 10]
The synchronous machine control device according to
claim 9, wherein the second command voltage computation
unit creates the second voltage command by using a primary
delay controller.
[Claim 11]
The synchronous machine control device according to
claim 10, wherein the primary delay controller sets a
reciprocal of a cutoff frequency in a current control
system as a time constant.
[Claim 12]
A synchronous machine control method for controlling
a power converter that supplies electric power to a
synchronous machine, the synchronous machine control method
comprising:
computing a first magnetic flux command value from a
current command value of the synchronous machine;
estimating a magnetic flux value of the synchronous
40
machine from a current detection value of the synchronous
machine; and
creating a voltage command value of the power
converter such that the first magnetic flux command value
coincides with the magnetic flux value.
[Claim 13]
An electric vehicle comprising:
a wheel;
a synchronous machine that drives the wheel;
a power converter that supplies electric power to the
synchronous machine; and
a control device that controls the power converter,
wherein the control device is the synchronous machine
control device described in claim 1.