FORM 2 THE PATENTS ACT, 1970
(39 of& 1970) THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ELECTRIC VEHICLE CONTROLLER;
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.
2
DESCRIPTION
Field
[0001] The present invention relates to an electric
5 vehicle controller applied to an electric vehicle driven by
a plurality of induction motors that is driven by one
inverter.
Background
10 [0002] As illustrated in Patent Literature 1 below, a
conventional electric vehicle controller typically drives
an electric vehicle by controlling torque generated by a
motor that is connected to an axle of wheels mounted on a
bogie of a motor car via a gear and a coupling. An
15 induction motor is typically used as the motor.
[0003] Patent Literature 2 below discloses an electric
vehicle controller that prevents an abnormal increase in
the rotational speed of a motor by stopping the operation
of an inverter when the rotational speed of the motor
20 detected by a speed sensor exceeds the maximum speed set
value.
Citation List
Patent Literature
25 [0004] Patent Literature 1: Japanese Patent Application
Laid-open No. 2011-173441
Patent Literature 2: Japanese Patent Application Laidopen
No. 2014-158419
30 Summary
Technical Problem
[0005] In an electric vehicle, a coupling that serves as
a connecting member for connecting an induction motor and a
3
gear may be disconnected during travel. Meanwhile, an
electric vehicle driven by a plurality of induction motors
is subjected to traction by induction motors whose
couplings are not disconnected even if some of the
5 plurality of induction motors are disconnected.
[0006] In the control that uses the value detected by
the speed sensor as in Patent Literature 2 above, the
rotational speeds of the axles to which the induction
motors are connected can be detected individually. Thus,
10 disconnection of the coupling can easily be detected by
detecting a difference in the rotational speeds of the
axles. On the other hand, in an electric vehicle
controller performing so-called speed sensorless control
that does not use a value detected by a speed sensor for
15 control, the rotational speeds of the axles to which the
induction motors are connected cannot be detected
individually. Thus, in the electric vehicle controller
performing the speed sensorless control, there is a need
for a technique that detects disconnection of the coupling
20 by an easy method.
[0007] The present invention has been made in view of
the above, and an object of the present invention is to
provide an electric vehicle controller that can detect
disconnection of a coupling by an easy method.
25
Solution to Problem
[0008] In order to solve the above problem and achieve
the object, the present invention includes a drive control
system including a plurality of induction motors, one
30 inverter that drives the plurality of the induction motors,
a current detector that detects a total current that is a
sum of motor currents flowing to corresponding ones of the
induction motors, and a controller that controls the
4
inverter on the basis of a current command value calculated
on the basis of a torque command value, a voltage command
value calculated on the basis of the total current detected,
and an estimated speed value calculated on the basis of the
5 voltage command value calculated and the total current
detected. Travel of an electric vehicle is controlled by
the drive control system. The controller includes a
coupling disconnection detecting unit that calculates an
estimated torque value on the basis of the total current
10 and the voltage command value, and detects disconnection of
a coupling provided between the induction motors and a
drive mechanism of the electric vehicle on the basis of the
estimated torque value calculated and the torque command
value.
15
Advantageous Effects of Invention
[0009] According to the present invention, the electric
vehicle controller can detect disconnection of the coupling
by an easy method.
20
Brief Description of Drawings
[0010] FIG. 1 is a block diagram of an electric vehicle
drive system including an electric vehicle controller
according to a first embodiment.
25 FIG. 2 is a diagram illustrating a schematic
configuration of a drive mechanism between a wheel and an
induction motor of an electric vehicle.
FIG. 3 is a block diagram illustrating a detailed
configuration of a controller according to the first
30 embodiment.
FIG. 4 is a flowchart illustrating an operation flow
for detecting coupling disconnection in the first
embodiment.
5
FIG. 5 is a block diagram illustrating an example of
the configuration of the controller according to the first
embodiment, the configuration being different from that of
FIG. 3.
5 FIG. 6 is a block diagram illustrating a detailed
configuration of a controller according to a second
embodiment.
FIG. 7 is a flowchart illustrating an operation flow
for detecting coupling disconnection in the second
10 embodiment.
FIG. 8 is a block diagram illustrating a detailed
configuration of a controller according to a third
embodiment.
FIG. 9 is a flowchart illustrating an operation flow
15 for detecting coupling disconnection in the third
embodiment.
FIG. 10 is a block diagram illustrating an example of
a hardware configuration that implements the functions of a
coupling disconnection detecting unit in the first, second,
20 and third embodiments.
FIG. 11 is a block diagram illustrating another
example of the hardware configuration that implements the
functions of the coupling disconnection detecting unit in
the first, second, and third embodiments.
25
Description of Embodiments
[0011] An electric vehicle controller according to
embodiments of the present invention will now be described
in detail with reference to the drawings. Note that the
30 present invention is not limited to the following
embodiments. Also, in the following description, physical
connection and electrical connection are not distinguished
from each other, and are simply referred to as “connection”.
6
[0012] First Embodiment.
FIG. 1 is a block diagram of an electric vehicle drive
system 80 including an electric vehicle controller
according to a first embodiment. FIG. 1 is an example of
5 application to a DC electric vehicle. As illustrated in
FIG. 1, the electric vehicle drive system 80 according to
the first embodiment includes an input circuit 3, a first
drive group 50, and a second drive group 52. The first
drive group 50 constitutes a first drive control system,
10 and the second drive group 52 constitutes a second drive
control system. The first drive group 50 and the second
drive group 52 control travel of the electric vehicle.
[0013] On the input side of the input circuit 3, a
positive side of the input circuit 3 is connected to an
15 overhead line 11 via a pantograph 15, and a negative side
of the input circuit 3 is in contact with a rail 18 via a
wheel 16. The first drive group 50 and the second drive
group 52 are connected in parallel on the output side of
the input circuit 3. These connections form one electric
20 circuit including the overhead line 11, the pantograph 15,
the input circuit 3, the first drive group 50, the wheel 16,
and the rail 18. Another electric circuit is formed
including the overhead line 11, the pantograph 15, the
input circuit 3, the second drive group 52, the wheel 16,
25 and the rail 18.
[0014] The input circuit 3 is supplied with power from
the overhead line 11 via the pantograph 15. The power from
the overhead line 11 via the pantograph 15 and the input
circuit 3 is also supplied to the first drive group 50 and
30 the second drive group 52.
[0015] The input circuit 3 includes a circuit breaker 22,
a filter capacitor 24, and a voltage detector 26. The
circuit breaker 22 opens or closes the connection between
7
the overhead line 11, and the first drive group 50 and the
second drive group 52. The filter capacitor 24 smooths and
stores the power supplied from the overhead line 11. The
voltage detector 26 detects a voltage of the filter
5 capacitor 24.
[0016] The first drive group 50 includes an inverter 1,
two induction motors 2, a controller 4, and a current
detector 5.
[0017] A connection terminal of the inverter 1 on a high
10 potential side is connected to the pantograph 15 via the
circuit breaker 22 of the input circuit 3, and a connection
terminal of the inverter 1 on a low potential side is
electrically connected to the wheel 16 through the input
circuit 3. The inverter 1 is a power converter that
15 converts DC supplied from the input circuit 3 into AC with
variable voltage and frequency. The two induction motors 2
are connected to an AC side of the inverter 1. Note that
for the inverter 1, the side corresponding to the input
circuit 3 is referred to as a “DC side”, and the side
20 corresponding to the induction motors 2 is referred to as
the “AC side”. The inverter 1 drives the two induction
motors 2. The two induction motors 2 provide a driving
force to the electric vehicle.
[0018] The current detector 5 is disposed between the
25 inverter 1 and a connection point 9 of the two induction
motors 2. The current detector 5 detects total currents iu,
iv, and iw being a sum of motor currents flowing to the two
induction motors 2. The motor current is a phase current
flowing in each phase of one induction motor 2. The total
30 currents iu, iv, and iw detected by the current detector 5
are input to the controller 4.
[0019] The controller 4 receives a filter capacitor
voltage vFC, which is a value detected by the voltage
8
detector 26, in addition to the total currents iu, iv, and
iw described above. The controller 4 generates gate drive
signals for driving a switching element 1a of the inverter
1 on the basis of the information on the total currents iu,
5 iv, and iw, rotational speed ωd, and the filter capacitor
voltage vFC, and outputs the gate drive signals to the
inverter 1. The controller 4 generates therein pulse width
modulation (PWM) signals for performing PWM control on the
inverter 1 serving as the power converter. The gate drive
10 signals are generated using the PWM signals.
[0020] The second drive group 52 is configured similarly
to the first drive group 50. Each component of the second
drive group 52 is the same as that of the first drive group
50, whereby a description thereof will be omitted.
15 [0021] Although FIG. 1 is the example of application to
the DC electric vehicle, the present invention is also
applicable to an AC electric vehicle. In the case of the
AC electric vehicle, the input circuit 3 has a different
configuration, but the controller 4 has an equivalent basic
20 configuration. Moreover, although FIG. 1 illustrates two
drive groups including the first drive group 50 and the
second drive group 52, it is needless to say that the
present invention can be applied to three or more drive
groups. Also, although FIG. 1 illustrates the example in
25 which the two induction motors 2 are connected to the one
inverter 1, the present invention is not limited to this
example. A vehicle on which the induction motor 2 is
mounted typically has a configuration in which one vehicle
has two bogies with two induction motors mounted on each
30 bogie. Therefore, when one controller 4 is mounted on one
vehicle in this typical configuration, the one controller 4
drives four of the induction motors 2.
[0022] As described above, the electric vehicle drive
9
system 80 according to the first embodiment has the
configuration in which the one inverter 1 drives the
plurality of induction motors 2 that drives the electric
vehicle. The controller 4 is included in the electric
5 vehicle controller according to the first embodiment.
Moreover, the electric vehicle drive system 80 according to
the first embodiment is not provided with a speed sensor
for detecting the rotational speed of the induction motors
2. That is, the controller 4 according to the first
10 embodiment is a controller that performs so-called speed
sensorless control that does not use a value detected by a
speed sensor for control. Note that the function of the
controller 4 is the same in each drive group. Therefore,
the following description focuses on one of the controllers
15 4 that controls one of the drive groups.
[0023] FIG. 2 is a diagram illustrating a schematic
configuration of a drive mechanism between the wheel 16 and
the induction motor 2 of the electric vehicle. As
illustrated in FIG. 2, a coupling 54 as a connecting member
20 is provided on a rotary shaft 53 of the induction motor 2,
and is connected to a motor-side gear 55. A wheel-side
gear 56 is disposed to be in mesh with the motor-side gear
55. The wheel-side gear 56 is fixed to an axle 57. The
motor-side gear 55 and the wheel-side gear 56 are included
25 as gears of the electric vehicle. The wheel 16 is
connected to the axle 57. Thus, the output side of the
induction motor 2 is provided with a mechanism for
conveying the mechanical output of the induction motor 2 to
the wheel 16 via the axle 57. The electric vehicle drives
30 the wheel 16 to rotate, and travels on the rail 18 with
which the wheel 16 is in contact.
[0024] FIG. 3 is a block diagram illustrating a detailed
configuration of the controller 4 according to the first
10
embodiment. In FIG. 3, a part identical or equivalent to a
part illustrated in FIG. 1 is indicated with the same
reference numeral as that assigned to the part in FIG. 1.
[0025] The controller 4 includes a gate drive circuit 8,
5 a voltage controller 30, and a coupling disconnection
detecting unit 40.
[0026] The gate drive circuit 8 generates the gate drive
signals for driving the switching element 1a of the
inverter 1 and outputs the gate drive signals to the
10 inverter 1. The voltage controller 30 generates the PWM
signals for performing PWM control on the inverter 1 and
outputs the PWM signals to the gate drive circuit 8. The
coupling disconnection detecting unit 40 detects whether or
not coupling disconnection has occurred in the induction
15 motor 2 to be driven.
[0027] The voltage controller 30 includes a torque
command value calculation unit 31, a current command value
calculation unit 32, a voltage command value calculation
unit 33, an integrator 34, a PWM control unit 35, a
20 coordinate transformation unit 36, and a speed estimation
unit 38.
[0028] The coordinate transformation unit 36 transforms
the total currents iu, iv, and iw detected by the current
detector 5 into current values corresponding to d-axis and
25 q-axis that are two axes in a rotating reference frame.
The current values obtained after transformation are d-axis
current id and q-axis current iq. The d-axis is an axis
called a flux axis, and the q-axis is an axis called a
torque axis. The d-axis and q-axis are in orthogonal
30 relationship in terms of vectors. The transformation
processing performed by the coordinate transformation unit
36 is known, and a description thereof will be omitted.
The d-axis current id and the q-axis current iq obtained
11
after the transformation by the coordinate transformation
unit 36 are input to the voltage command value calculation
unit 33, the speed estimation unit 38, and the coupling
disconnection detecting unit 40.
5 [0029] A start command Cs is input to the torque command
value calculation unit 31. The start command Cs is a
command that is output when traveling of the electric
vehicle is to be started. The torque command value
calculation unit 31 calculates a torque command value Tm*
10 upon being triggered by the input of the start command Cs.
The torque command value Tm* is a command value of the
torque to be output by the induction motors 2.
[0030] The torque command value Tm* calculated by the
torque command value calculation unit 31 is input to the
15 current command value calculation unit 32. On the basis of
the torque command value Tm*, the current command value
calculation unit 32 calculates a q-axis current command
value iq* that is a current command value for the torque
axis, and a d-axis current command value id* that is a
20 current command value for the flux axis. The calculation
processing in the current command value calculation unit 32
is known, and a description thereof will be omitted. The
q-axis current command value iq* and the d-axis current
command value id* calculated by the current command value
25 calculation unit 32 are input to the voltage command value
calculation unit 33.
[0031] The voltage command value calculation unit 33
calculates a d-axis voltage command value vd* and a q-axis
voltage command value vq* on the basis of the d-axis
30 current command value id* and q-axis current command value
iq* calculated by the current command value calculation
unit 32, and on the basis of the d-axis current id and qaxis
current iq output from the coordinate transformation
12
unit 36. The voltage command value is a command value of
the voltage output by the inverter 1. In the case of
vector control, a general method is to perform calculations
separately in the d-axis direction and the q-axis direction.
5 The calculation processing in the voltage command value
calculation unit 33 is known, and a description thereof
will be omitted. The d-axis voltage command value vd* and
q-axis voltage command value vq* calculated by the voltage
command value calculation unit 33 are input to the PWM
10 control unit 35, the speed estimation unit 38, and the
coupling disconnection detecting unit 40.
[0032] To the speed estimation unit 38, the d-axis
current id and q-axis current iq obtained by the
transformation by the coordinate transformation unit 36,
15 and the d-axis voltage command value vd* and q-axis voltage
command value vq* calculated by the voltage command value
calculation unit 33, are input. The speed estimation unit
38 calculates an estimated speed value ωe on the basis of
the d-axis current id and q-axis current iq, and the d-axis
20 voltage command value vd* and q-axis voltage command value
vq*. The estimated speed value ωe calculated by the speed
estimation unit 38 is input to the integrator 34. Note
that a method of calculating the estimated speed value ωe
is known, and a detailed description thereof will be
25 omitted. For a specific method of calculation, refer to
the content of the publication disclosed in Japanese Patent
No. 4437629, for example.
[0033] The integrator 34 calculates an angular frequency
by internal calculation on the basis of the estimated speed
30 value ωe being input, and integrates the calculated angular
frequency to calculate a phase θi. The angular frequency
can be generated by adding the slip velocity of the
induction motors 2 to the estimated speed value ωe. The
13
phase θi calculated by the integrator 34 is input to the
PWM control unit 35 and the coordinate transformation unit
36. The coordinate transformation unit 36 uses the phase
θi when calculating the d-axis current id and the q-axis
5 current iq.
[0034] The PWM control unit 35 generates the PWM signals
for performing PWM control on the switching element 1a of
the inverter 1 on the basis of the phase θi, the d-axis
voltage command value vd* and q-axis voltage command value
10 vq*, and the filter capacitor voltage vFC. The processing
of generating the PWM signals is known, and a description
thereof will be omitted.
[0035] Next, the coupling disconnection detecting unit
40 will be described. As illustrated in FIG. 3, the
15 coupling disconnection detecting unit 40 includes a torque
estimation unit 41, a deviation calculation unit 42, and a
determination unit 43.
[0036] The coupling disconnection detecting unit 40 is a
detection unit that detects disconnection of the coupling
20 54 provided on the rotary shaft 53 of the induction motor 2.
When the induction motor 2 with the coupling 54
disconnected is driven, there is a difference between the
torque command value Tm* calculated on the basis of the
start command Cs and an estimated torque value Te
25 calculated on the basis of the total currents iu, iv, and iw
detected by the current detector 5, and coupling
disconnection can be detected by the difference. The
difference is particularly noticeable at startup. Note
that “at startup” includes not only a case where the
30 vehicle shifts from rest to a traveling state, but also a
case where the vehicle accelerates again from a coasting
state. Moreover, the difference in this case is not a
difference caused by accident or error, but a significant
14
difference. The coupling disconnection detecting unit 40
illustrated in FIG. 3 is configured using this principle.
[0037] To the torque estimation unit 41, the d-axis
current id and q-axis current iq obtained by the
5 transformation by the coordinate transformation unit 36,
the d-axis voltage command value vd* and q-axis voltage
command value vq* calculated by the voltage command value
calculation unit 33, and the start command Cs, are input.
When the start command Cs is input, the torque estimation
10 unit 41 calculates the estimated torque value Te on the
basis of the d-axis current id, the q-axis current iq, the
d-axis voltage command value vd*, and the q-axis voltage
command value vq*. The estimated torque value Te is not a
value input or instructed from outside, but an estimated
15 value of torque calculated by a control parameter inside
the controller 4. The estimated torque value Te calculated
by the torque estimation unit 41 is input to the deviation
calculation unit 42.
[0038] To the deviation calculation unit 42, the torque
20 command value Tm* is input in addition to the estimated
torque value Te. The deviation calculation unit 42
calculates an absolute value |ΔT| of the deviation between
the torque command value Tm* and the estimated torque value
Te. The absolute value |ΔT| of the deviation is input to
25 the determination unit 43.
[0039] To the determination unit 43, a reference value
Ts is input in addition to the absolute value |ΔT| of the
deviation. The reference value Ts is a threshold for
detecting coupling disconnection. The determination unit
30 43 compares the absolute value |ΔT| of the deviation with
the reference value Ts, and determines that coupling
disconnection has occurred when the absolute value |ΔT| of
the deviation is larger than the reference value Ts. The
15
determination unit 43 outputs a disconnection detection
signal Hd when determining that coupling disconnection has
occurred. The disconnection detection signal Hd is output
to the gate drive circuit 8. The disconnection detection
5 signal Hd is a control signal for forcibly stopping the
operation of the gate drive circuit 8. While the
disconnection detection signal Hd is being output, the gate
drive circuit 8 stops outputting the gate drive signals to
the inverter 1 even if the PWM signals are input from the
10 PWM control unit 35.
[0040] Note that although the coupling disconnection
detecting unit 40 above is configured to input the start
command Cs to the torque estimation unit 41, the start
command Cs may be input to the determination unit 43. In
15 the case of this configuration, the processings by the
torque estimation unit 41, the deviation calculation unit
42, and the determination unit 43 are always performed
regardless of the input of the start command Cs. Then,
with the input of the start command Cs, a result of
20 determination by the determination unit 43 is output to the
gate drive circuit 8. Alternatively, regardless of the
input of the start command Cs, the processings by the
torque estimation unit 41 and the deviation calculation
unit 42 are always performed. Then, with the input of the
25 start command Cs, the determination unit 43 starts the
operation, and a result of determination by the
determination unit 43 is output to the gate drive circuit 8.
[0041] Next, an operation of detecting coupling
disconnection in the first embodiment will be described
30 with reference to FIGS. 3 and 4. FIG. 4 is a flowchart
illustrating an operation flow for detecting coupling
disconnection in the first embodiment. In FIG. 4, the
processings in steps S101 and S102 are executed by the
16
torque estimation unit 41, the processing in step S103 is
executed by the deviation calculation unit 42, and the
processings in steps S104 to S107 are executed by the
determination unit 43.
5 [0042] In step S101, it is determined whether or not the
start command Cs has been received. If the start command
Cs has not been received (No in step S101), the processing
in step S101 is repeated. If the start command Cs has been
received (Yes in step S101), the processing proceeds to
10 step S102.
[0043] In step S102, the estimated torque value Te is
calculated. In step S103, the deviation ΔT between the
estimated torque value Te and the torque command value Tm*
is calculated. In step S104, the absolute value |ΔT| of
15 the deviation ΔT calculated in step S103 is compared with
the reference value Ts.
[0044] Here, if the absolute value |ΔT| is greater than
or equal to the reference value Ts (Yes in step S105), the
processing proceeds to step S106. In step S106, it is
20 determined that “coupling disconnection has occurred”, and
the processing flow in FIG. 4 is ended.
[0045] On the other hand, if the absolute value |ΔT| is
less than the reference value Ts (No in step S105), the
processing proceeds to step S107. In step S107, it is
25 determined that “coupling disconnection has not occurred”,
and the processing flow in FIG. 4 is ended.
[0046] Note that in the determination processing in step
S105 above, if the absolute value |ΔT| is equal to the
reference value Ts, the determination is “Yes” and the
30 processing proceeds to step S106, but the determination may
be “No” and the processing may proceed to step S107. That
is, the determination may be either “Yes” or “No” if the
absolute value |ΔT| is equal to the reference value Ts.
17
[0047] As described above, the electric vehicle
controller according to the first embodiment can detect
coupling disconnection of the induction motors 2 on the
basis of the torque command value Tm* and the estimated
5 torque value Te. The method of the first embodiment need
only use command information about the torque that is the
torque command value Tm* and estimated information about
the torque that is the estimated torque value Te, whereby
coupling disconnection of the induction motors 2 can be
10 detected by a simple method.
[0048] Moreover, the electric vehicle controller
according to the first embodiment can detect coupling
disconnection of some of the plurality of induction motors
2, and stop the drive of the drive group including the
15 induction motor 2 for which coupling disconnection has been
detected. As a result, even when the drive of only one
drive group including the induction motor 2 experiencing
coupling disconnection is stopped, the operation of the
electric vehicle can be continued by another drive group.
20 [0049] FIG. 5 is a block diagram illustrating an example
of the configuration of the controller 4 according to the
first embodiment, the configuration being different from
that of FIG. 3. The difference from FIG. 3 is the
destination to which the disconnection detection signal Hd
25 is output. That is, the disconnection detection signal Hd
is output to the gate drive circuit 8 in FIG. 3, whereas in
FIG. 5, the disconnection detection signal Hd is output to
the circuit breaker 22. The circuit breaker 22 that has
received the disconnection detection signal Hd cuts off the
30 power supplied from the overhead line 11 by opening a
contact (not shown).
[0050] The configuration of FIG. 3 has an advantage that
the operation of the electric vehicle can be continued. On
18
the other hand, the configuration of FIG. 5 cannot stop the
drive of only one drive group including the induction motor
2 experiencing coupling disconnection, thereby not being
able to continue the operation of the electric vehicle.
5 However, the configuration of FIG. 5 has an advantage in
that the operation of the electric vehicle can be stopped
promptly because the power supply can be cut off on the
side closer to the overhead line 11. In the electric
vehicle, a decrease in the number of induction motors 2
10 that can contribute to driving of the vehicle results in an
increase in the load on one induction motor 2. Therefore,
an unintended large current may flow through each induction
motor 2. The configuration of FIG. 5 is effective for
avoiding such a situation.
15 [0051] Second Embodiment.
FIG. 6 is a block diagram illustrating a detailed
configuration of a controller 4A according to a second
embodiment. The controller 4A according to the second
embodiment includes a voltage controller 30A and a coupling
20 disconnection detecting unit 40A.
[0052] The coupling disconnection detecting unit 40A is
obtained by changing the configurations of the coupling
disconnection detecting unit 40 of the first embodiment
illustrated in FIG. 3 from the torque estimation unit 41 to
25 a speed conversion unit 44, the deviation calculation unit
42 to a deviation calculation unit 45, and the
determination unit 43 to a determination unit 46. Note
that the other configurations are identical or equivalent
to those of the first embodiment except for input/output
30 signals and are thus denoted by the same reference numerals
as those in the first embodiment, whereby a redundant
description will be omitted. The input/output signals will
be described later.
19
[0053] The coupling disconnection detecting unit 40A is
a detection unit that detects disconnection of the coupling
54 provided on the rotary shaft 53 of the induction motor 2.
When the induction motor 2 with the coupling 54
5 disconnected is driven, there is a difference between the
actual rotational speed of the induction motor 2 and the
estimated speed value ωe calculated on the basis of the
total currents iu, iv, and iw detected by the current
detector 5, and coupling disconnection can be detected by
10 the difference. The difference is particularly noticeable
at startup. The coupling disconnection detecting unit 40A
illustrated in FIG. 5 is configured using this principle.
[0054] A vehicle speed Vs, which is vehicle speed
information from outside, is input to the speed conversion
15 unit 44. As the vehicle speed information, information on
the traveling speed managed by a train or actual detected
information about the traveling speed may be used. The
speed conversion unit 44 converts the vehicle speed Vs into
a converted speed ωc. The converted speed ωc is a
20 converted value obtained by converting the vehicle speed Vs
into the rotational speed of the induction motor 2. The
converted speed ωc calculated by the speed conversion unit
44 is input to the deviation calculation unit 45.
[0055] The deviation calculation unit 45 receives the
25 estimated speed value ωe in addition to the converted speed
ωc. The deviation calculation unit 45 calculates an
absolute value |Δω| of a deviation between the converted
speed ωc and the estimated speed value ωe. The absolute
value |Δω| of the deviation is input to the determination
30 unit 46.
[0056] To the determination unit 46, a reference value
ωs is input in addition to the absolute value |Δω| of the
deviation. The reference value ωs is a threshold for
20
detecting coupling disconnection. The determination unit
46 compares the absolute value |Δω| of the deviation with
the reference value ωs, and determines that coupling
disconnection has occurred when the absolute value |Δω| of
5 the deviation is larger than the reference value ωs,
thereby outputting the disconnection detection signal Hd to
the gate drive circuit 8. Note that the disconnection
detection signal Hd is output to the gate drive circuit 8
in FIG. 6, but may be output to the circuit breaker 22 as
10 in FIG. 5.
[0057] Note that although the coupling disconnection
detecting unit 40A above is configured to input the start
command Cs to the speed conversion unit 44, the start
command Cs may be input to the determination unit 46. In
15 the case of this configuration, the processings by the
speed conversion unit 44, the deviation calculation unit 45,
and the determination unit 46 are always performed
regardless of the input of the start command Cs. Then,
with the input of the start command Cs, a result of
20 determination by the determination unit 46 is output to the
gate drive circuit 8. Alternatively, regardless of the
input of the start command Cs, the processings by the speed
conversion unit 44 and the deviation calculation unit 45
are always performed. Then, with the input of the start
25 command Cs, the determination unit 46 starts the operation,
and a result of determination by the determination unit 46
is output to the gate drive circuit 8.
[0058] Next, an operation of detecting coupling
disconnection in the second embodiment will be described
30 with reference to FIGS. 6 and 7. FIG. 7 is a flowchart
illustrating an operation flow for detecting coupling
disconnection in the second embodiment. In FIG. 7, the
processings in steps S201 and S202 are executed by the
21
speed conversion unit 44, the processing in step S203 is
executed by the deviation calculation unit 45, and the
processings in steps S204 to S207 are executed by the
determination unit 46.
5 [0059] In step S201, it is determined whether or not the
start command Cs has been received. If the start command
Cs has not been received (No in step S201), the processing
in step S201 is repeated. If the start command Cs has been
received (Yes in step S201), the processing proceeds to
10 step S202.
[0060] In step S202, the vehicle speed Vs is converted
into the converted speed ωc. In step S203, the deviation
Δω between the estimated speed value ωe and the converted
speed ωc is calculated. In step S204, the absolute value
15 |Δω| of the deviation Δω calculated in step S203 is
compared with the reference value ωs. The reference value
ωs is set as a criterion value for preventing false
detection due to noise or the like. That is, the reference
value ωs is a set value provided for improving the accuracy
20 of the detection of coupling disconnection.
[0061] Here, if the absolute value |Δω| is greater than
or equal to the reference value ωs (Yes in step S205), the
processing proceeds to step S206. In step S206, it is
determined that “coupling disconnection has occurred”, and
25 the processing flow in FIG. 7 is ended.
[0062] On the other hand, if the absolute value |Δω| is
less than the reference value ωs (No in step S205), the
processing proceeds to step S207. In step S207, it is
determined that “coupling disconnection has not occurred”,
30 and the processing flow in FIG. 7 is ended.
[0063] Note that in the determination processing in step
S205 above, if the absolute value |Δω| is equal to the
reference value ωs, the determination is “Yes” and the
22
processing proceeds to step S206, but the determination may
be “No” and the processing may proceed to step S207. That
is, the determination may be either “Yes” or “No” if the
absolute value |Δω| is equal to the reference value ωs.
5 [0064] As described above, the electric vehicle
controller according to the second embodiment can detect
coupling disconnection of the induction motors 2 on the
basis of the vehicle speed Vs and the estimated speed value
ωe. The method of the second embodiment need only use
10 input information about the speed that is the vehicle speed
Vs and estimated information about the speed that is the
estimated speed value ωe, whereby coupling disconnection of
the induction motors 2 can be detected by a simple method.
[0065] Moreover, the electric vehicle controller
15 according to the second embodiment can detect coupling
disconnection of some of the plurality of induction motors
2, and stop the drive of the drive group including the
induction motor 2 for which coupling disconnection has been
detected. As a result, even when the drive of only one
20 drive group including the induction motor 2 experiencing
coupling disconnection is stopped, the operation of the
electric vehicle can be continued by another drive group.
[0066] Note that although the disconnection detection
signal Hd is output to the gate drive circuit 8 in FIG. 6,
25 the disconnection detection signal Hd may be output to the
circuit breaker 22 as in FIG. 5. Outputting the
disconnection detection signal Hd to the circuit breaker 22
can obtain the effect of the configuration illustrated in
FIG. 5 described in the first embodiment.
30 [0067] Third Embodiment.
FIG. 8 is a block diagram illustrating a detailed
configuration of a controller 4B according to a third
embodiment. The controller 4B according to the third
23
embodiment includes a voltage controller 30B and a coupling
disconnection detecting unit 40B.
[0068] The coupling disconnection detecting unit 40B is
obtained by changing the configurations of the coupling
5 disconnection detecting unit 40A of the second embodiment
illustrated in FIG. 6 from the speed conversion unit 44 to
a current value conversion unit 47, the deviation
calculation unit 45 to a deviation calculation unit 48, and
the determination unit 46 to a determination unit 49.
10 [0069] Moreover, the controller 4B according to the
third embodiment has a configuration in which current
detectors 5a and 5b are provided between the connection
point 9 and the induction motors 2 instead of the
configuration in which the current detector 5 is provided
15 between the inverter 1 and the connection point 9. The
voltage controller 30B is adapted to this configuration by
replacing the coordinate transformation unit 36 with
coordinate transformation units 36a and 36b and adding an
adder 39. Also, FIG. 8 is adapted to this configuration by
20 denoting the induction motor on the side of the current
detector 5a as an induction motor 2a, and the induction
motor on the side of the current detector 5b as an
induction motor 2b.
[0070] Note that the other configurations are identical
25 or equivalent to those of the second embodiment and are
thus denoted by the same reference numerals as those in the
second embodiment, whereby a redundant description will be
omitted.
[0071] In the configuration of FIG. 8, the current
30 detector 5a detects individual motor currents iu1, iv1, and
iw1 flowing to the induction motor 2a. The current
detector 5b detects individual motor currents iu2, iv2, and
iw2 flowing to the induction motor 2b.
24
[0072] The detected values of the motor currents iu1, iv1,
and iw1 detected by the current detector 5a are input to
the coordinate transformation unit 36a. The coordinate
transformation unit 36a transforms the motor currents iu1,
5 iv1, and iw1 detected by the current detector 5a into d-axis
and q-axis current values. The current values obtained
after transformation are d-axis current id1 and q-axis
current iq1. The d-axis current id1 and the q-axis current
iq1 obtained after transformation by the coordinate
10 transformation unit 36a are input to the adder 39. Also,
out of the d-axis current id1 and the q-axis current iq1,
the q-axis current iq1 is input to the deviation
calculation unit 48 of the coupling disconnection detecting
unit 40B.
15 [0073] The detected values of the motor currents iu2, iv2,
and iw2 detected by the current detector 5b are input to
the coordinate transformation unit 36b. The coordinate
transformation unit 36b transforms the motor currents iu2,
iv2, and iw2 detected by the current detector 5b into d-axis
20 and q-axis current values. The current values obtained
after transformation are d-axis current id2 and q-axis
current iq2. The d-axis current id2 and the q-axis current
iq2 obtained after transformation by the coordinate
transformation unit 36b are input to the adder 39. Also,
25 out of the d-axis current id2 and the q-axis current iq2,
the q-axis current iq2 is input to the deviation
calculation unit 48 of the coupling disconnection detecting
unit 40B.
[0074] The adder 39 adds the d-axis current id1 and the
30 d-axis current id2, adds the q-axis current iq1 and the qaxis
current iq2, and outputs the added values to the
voltage command value calculation unit 33 and the speed
estimation unit 38. The output of the adder 39 is the d25
axis current id and the q-axis current iq obtained by
adding the motor currents flowing to the induction motor 2a
and the motor currents flowing to the induction motor 2b.
[0075] The coupling disconnection detecting unit 40B is
5 a detection unit that detects disconnection of the coupling
54 provided on the rotary shaft 53 of the induction motor 2.
When the induction motor 2 with the coupling 54
disconnected is driven, there is a difference between the
actual motor currents flowing to the individual induction
10 motors 2 and the q-axis current command value iq*
calculated on the basis of the torque command value Tm*,
and coupling disconnection can be detected by the
difference. The difference is particularly noticeable at
startup. Also, the difference is particularly noticeable
15 in the q-axis current component. The coupling
disconnection detecting unit 40B illustrated in FIG. 8 is
configured using this principle.
[0076] To the current value conversion unit 47, the qaxis
current command value iq* calculated by the current
20 command value calculation unit 32 and the start command Cs
are input. When the start command Cs is input, the current
value conversion unit 47 converts the q-axis current
command value iq*, which is a q-axis command value for the
motor currents flowing to the two induction motors 2a and
25 2b, into a q-axis current command value iq1* for either one
of the induction motor 2a and the induction motor 2b. The
q-axis current command value iq1* obtained after conversion
by the current value conversion unit 47 is input to the
deviation calculation unit 48.
30 [0077] In addition to the q-axis current command value
iq1*, to the deviation calculation unit 48, the q-axis
current iq1 obtained by transformation by the coordinate
transformation unit 36a and the q-axis current iq2 obtained
26
by transformation by the coordinate transformation unit 36b
are input. The deviation calculation unit 48 calculates an
absolute value |ΔI1| of a deviation between the q-axis
current command value iq1* and the q-axis current iq1, and
5 an absolute value |ΔI2| of a deviation between the q-axis
current command value iq2* and the q-axis current iq2. The
absolute values |ΔI1| and |ΔI2| of the deviations are input
to the determination unit 49.
[0078] To the determination unit 49, a reference value
10 Is is input in addition to the absolute values |ΔI1| and
|ΔI2| of the deviations. The reference value Is is a
threshold for detecting coupling disconnection. The
determination unit 49 compares each of the absolute values
|ΔI1| and |ΔI2| of the deviations with the reference value
15 Is. The determination unit 49 determines that coupling
disconnection has occurred in the induction motor 2a when
the absolute value |ΔI1| of the deviation is larger than
the reference value Is, thereby outputting the
disconnection detection signal Hd to the gate drive circuit
20 8. Also, the determination unit 49 determines that
coupling disconnection has occurred in the induction motor
2b when the absolute value |ΔI2| of the deviation is larger
than the reference value Is, thereby outputting the
disconnection detection signal Hd to the gate drive circuit
25 8. Note that the disconnection detection signal Hd is
output to the gate drive circuit 8 in FIG. 8, but may be
output to the circuit breaker 22 as in FIG. 5.
[0079] FIG. 8 illustrates the configurations in which
the q-axis current command value iq* is input to the
30 current value conversion unit 47, and the q-axis current
command value iq1*, the q-axis current iq1, and the q-axis
current iq2 are input to the deviation calculation unit 48,
but the present invention is not limited to these
27
configurations. In addition to these configurations, the
d-axis current command value id* may be input to the
current value conversion unit 47, and the d-axis current
command value id1*, the d-axis current id1, and the d-axis
5 current id2 may be input to the deviation calculation unit
48. That is, in addition to the command values and the
current values of the q-axis current, the command values
and the current values of the d-axis current may be used
for the determination of coupling disconnection.
10 [0080] Moreover, although the coupling disconnection
detecting unit 40B above is configured to input the start
command Cs to the current value conversion unit 47, the
start command Cs may be input to the determination unit 49.
In the case of this configuration, the processings by the
15 current value conversion unit 47, the deviation calculation
unit 48, and the determination unit 49 are always performed
regardless of the input of the start command Cs. Then,
with the input of the start command Cs, a result of
determination by the determination unit 49 is output to the
20 gate drive circuit 8. Alternatively, regardless of the
input of the start command Cs, the processings by the
current value conversion unit 47 and the deviation
calculation unit 48 are always performed. Then, with the
input of the start command Cs, the determination unit 49
25 starts the operation, and a result of determination by the
determination unit 49 is output to the gate drive circuit 8.
[0081] Next, an operation of detecting coupling
disconnection in the third embodiment will be described
with reference to FIGS. 8 and 9. FIG. 9 is a flowchart
30 illustrating an operation flow for detecting coupling
disconnection in the third embodiment. In FIG. 9, the
processings in steps S301 and S302 are executed by the
current value conversion unit 47, the processing in step
28
S303 is executed by the deviation calculation unit 48, and
the processings in steps S304 to S307 are executed by the
determination unit 49.
[0082] In step S301, it is determined whether or not the
5 start command Cs has been received. If the start command
Cs has not been received (No in step S301), the processing
in step S301 is repeated. If the start command Cs has been
received (Yes in step S301), the processing proceeds to
step S302.
10 [0083] In step S302, the q-axis current command value
iq* is converted into the q-axis current command value iq1*
for one motor. In step S303, deviations ΔI1 and ΔI2
between the q-axis current command values iq1* and iq2* and
the q-axis currents iq1 and iq2 calculated on the basis of
15 the detected values are calculated, respectively. In step
S304, the absolute values |ΔI1| and |ΔI2| of the deviations
ΔI1 and ΔI2 calculated in step S303 are compared with the
reference value Is.
[0084] Here, if at least one of the absolute values
20 |ΔI1| and |ΔI2| is larger than or equal to the reference
value Is (Yes in step S305), the processing proceeds to
step S306. In step S306, it is determined that “coupling
disconnection has occurred”, and the processing flow in FIG.
9 is ended.
25 [0085] On the other hand, if the absolute values |ΔI1|
and |ΔI2| are both less than the reference value Is (No in
step S305), the processing proceeds to step S307. In step
S307, it is determined that “coupling disconnection has not
occurred”, and the processing flow in FIG. 9 is ended.
30 [0086] Note that in the determination processing in step
S305 above, if the absolute values |ΔI1| and |ΔI2| are
equal to the reference value Is, the determination is “Yes”
and the processing proceeds to step S306, but the
29
determination may be “No” and the processing may proceed to
step S307. That is, the determination may be either “Yes”
or “No” if the absolute values |ΔI1| and |ΔI2| are equal to
the reference value Is.
5 [0087] As described above, the electric vehicle
controller according to the third embodiment can detect
coupling disconnection of the induction motors 2 on the
basis of the q-axis currents iq1 and iq2, which are
calculated on the basis of the detected values of the
10 individual motor currents flowing to the corresponding
induction motors 2a and 2b, and the q-axis current command
value iq1* for one motor calculated on the basis of the qaxis
current command value iq*. As described above, the qaxis
currents iq1 and iq2 can be calculated using the
15 detected values of the currents flowing to the
corresponding induction motors 2a and 2b. Accordingly, the
method of the third embodiment need only use a control
parameter that is the q-axis current command value iq* and
detected information of the current detectors 5a and 5b,
20 and thus can detect coupling disconnection of the induction
motors 2 by a simple method.
[0088] Moreover, the electric vehicle controller
according to the third embodiment can detect coupling
disconnection of the induction motor 2a or 2b, and stop the
25 drive of the drive group including the induction motor 2a
or 2b for which coupling disconnection has been detected.
As a result, even when the drive of only one drive group
including the induction motor 2a or 2b experiencing
coupling disconnection is stopped, the operation of the
30 electric vehicle can be continued by another drive group.
[0089] The electric vehicle controller according to the
third embodiment can also identify which of the induction
motors 2a and 2b has coupling disconnection. This can
30
achieve an effect that troubleshooting and maintenance work
are performed more easily than the electric vehicle
controllers of the first and second embodiments.
[0090] Note that although the disconnection detection
5 signal Hd is output to the gate drive circuit 8 in FIG. 8,
the disconnection detection signal Hd may be output to the
circuit breaker 22 as in FIG. 5. Outputting the
disconnection detection signal Hd to the circuit breaker 22
can obtain the effect of the configuration illustrated in
10 FIG. 5 described in the first embodiment.
[0091] Lastly, a hardware configuration that implements
the functions of the coupling disconnection detecting unit
40 in the first embodiment, the functions of the coupling
disconnection detecting unit 40A in the second embodiment,
15 and the functions of the coupling disconnection detecting
unit 40B in the third embodiment will be described with
reference to FIGS. 10 and 11.
[0092] When implementing each function of the coupling
disconnection detecting unit 40, the coupling disconnection
20 detecting unit 40A, or the coupling disconnection detecting
unit 40B, the hardware can include a processor 100 that
performs an arithmetic operation, a memory 102 that saves a
program read by the processor 100, and an interface 104
that inputs and outputs signals as illustrated in FIG. 10.
25 [0093] The processor 100 may be an arithmetic unit, a
microprocessor, a microcomputer, a central processing unit
(CPU), or a digital signal processor (DSP). The memory 102
can include, for example, a non-volatile or volatile
semiconductor memory such as a random access memory (RAM),
30 a read only memory (ROM), a flash memory, an erasable
programmable ROM (EPROM), or an electrically EPROM (EEPROM
(registered trademark)), a magnetic disk, a flexible disk,
an optical disk, a compact disc, a mini disc, or a digital
31
versatile disc (DVD).
[0094] The memory 102 stores a program that executes
each function of the coupling disconnection detecting unit
40, the coupling disconnection detecting unit 40A, or the
5 coupling disconnection detecting unit 40B. The processor
100 transmits and receives necessary information via the
interface 104 and also executes the program stored in the
memory 102, thereby executing various types of arithmetic
processing described in the first, second, and third
10 embodiments. A result of the processing by the processor
100 can be stored in the memory 102.
[0095] Moreover, the processor 100 and the memory 102
illustrated in FIG. 10 may be replaced with processing
circuitry 103 as in FIG. 11. The processing circuitry 103
15 corresponds to a single circuit, a complex circuit, a
programmed processor, a parallel-programmed processor, an
application specific integrated circuit (ASIC), a field
programmable gate array (FPGA), or a combination of those.
[0096] The configuration illustrated in the
20 aforementioned embodiment merely illustrates an example of
the content of the present invention, and can thus be
combined with another known technique or partially omitted
and/or modified without departing from the scope of the
present invention.
25
Reference Signs List
[0097] 1 inverter; 1a switching element; 2, 2a, 2b
induction motor; 3 input circuit; 4, 4A, 4B controller; 5,
5a, 5b current detector; 8 gate drive circuit; 9
30 connection point; 11 overhead line; 15 pantograph; 16
wheel; 18 rail; 22 circuit breaker; 24 filter capacitor;
26 voltage detector; 30, 30A, 30B voltage controller; 31
torque command value calculation unit; 32 current command
32
value calculation unit; 33 voltage command value
calculation unit; 34 integrator; 35 PWM control unit; 36,
36a, 36b coordinate transformation unit; 38 speed
estimation unit; 39 adder; 40, 40A, 40B coupling
5 disconnection detecting unit; 41 torque estimation unit;
42, 45, 48 deviation calculation unit; 43, 46, 49
determination unit; 44 speed conversion unit; 47 current
value conversion unit; 50 first drive group; 52 second
drive group; 53 rotary shaft; 54 coupling; 55 motor-side
10 gear; 56 wheel-side gear; 57 axle; 80 electric vehicle
drive system; 100 processor; 102 memory; 103 processing
circuitry; 104 interface.
33
We Claim:
1. An electric vehicle controller that includes a drive
5 control system and controls travel of an electric vehicle
by the drive control system, the drive control system
including a plurality of induction motors, one inverter to
drive the plurality of the induction motors, a current
detector to detect a total current that is a sum of motor
10 currents flowing to the induction motors, and a controller
to control the inverter on the basis of a current command
value calculated on the basis of a torque command value, a
voltage command value calculated on the basis of the total
current detected, and an estimated speed value calculated
15 on the basis of the voltage command value calculated and
the total current detected, wherein
the controller includes
a coupling disconnection detecting unit to calculate
an estimated torque value on the basis of the total current
20 and the voltage command value, and detect disconnection of
a coupling provided between the induction motors and a
drive mechanism of the electric vehicle on the basis of the
estimated torque value calculated and the torque command
value.
25
2. The electric vehicle controller according to claim 1,
wherein
the coupling disconnection detecting unit includes:
an estimation unit to estimate the estimated torque
30 value;
a calculation unit to calculate an absolute value of a
deviation between the torque command value and the
estimated torque value; and
34
a determination unit to compare the absolute value of
the deviation with a reference value, and determine that
coupling disconnection has occurred when the absolute value
of the deviation is larger than the reference value.
5
3. An electric vehicle controller that includes a drive
control system and controls travel of an electric vehicle
by the drive control system, the drive control system
including a plurality of induction motors, one inverter to
10 drive the plurality of the induction motors, a current
detector to detect a total current being a sum of motor
currents flowing to the induction motors, and a controller
to control the inverter on the basis of a voltage command
value calculated on the basis of a torque command value and
15 the total current detected, and an estimated speed value
calculated on the basis of the voltage command value
calculated and the total current detected, wherein
the controller includes
a coupling disconnection detecting unit to detect
20 disconnection of a coupling provided between the induction
motors and a drive mechanism of the electric vehicle on the
basis of the estimated speed value and a rotational speed
of the induction motors calculated using a traveling speed
of the electric vehicle.
25
4. The electric vehicle controller according to claim 3,
wherein
the coupling disconnection detecting unit includes:
a conversion unit to convert the traveling speed of
30 the electric vehicle into the rotational speed of the
induction motors;
a calculation unit to calculate an absolute value of a
deviation between the rotational speed and the estimated
35
speed value; and
a determination unit to compare the absolute value of
the deviation with a reference value, and determine that
coupling disconnection has occurred when the absolute value
5 of the deviation is larger than the reference value.
5. An electric vehicle controller that includes a drive
control system and controls travel of an electric vehicle
by the drive control system, the drive control system
10 including a plurality of induction motors, one inverter to
drive the plurality of the induction motors, a plurality of
current detectors to correspondingly detect individual
motor currents flowing to the induction motors, and a
controller to control the inverter on the basis of a
15 current command value calculated on the basis of a torque
command value, a voltage command value calculated on the
basis of an added value of the individual motor currents
detected, and an estimated speed value calculated on the
basis of the voltage command value calculated and the added
20 value of the motor currents, wherein
the controller includes
a coupling disconnection detecting unit to detect
disconnection of a coupling provided between each of the
induction motors and a drive mechanism of the electric
25 vehicle on the basis of a q-axis current calculated on the
basis of a detected value of each of the individual motor
currents flowing to each of the induction motors, and a qaxis
current command value of the current command value.
30 6. The electric vehicle controller according to claim 5,
wherein
the coupling disconnection detecting unit includes:
a conversion unit to convert the q-axis current
36
command value into a q-axis current command value for one
of the induction motors;
a calculation unit to calculate an absolute value of a
deviation between the q-axis current of each of the
5 induction motors and the q-axis current command value; and
a determination unit to compare the absolute value of
the deviation with a reference value, and determine that
coupling disconnection has occurred when the absolute value
of the deviation is larger than the reference value.