FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
RAILWAY VEHICLE POWER CONVERSION SYSTEM
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
5 Technical Field
[0001] The present disclosure relates to a railway vehicle power conversion system
that uses regenerative power to charge a power storage device.
Background Art
[0002] Power stored in a power storage device, that is mounted on an electric
10 railway vehicle traveling through a direct-current electrification section and stores
regenerative power generated by regenerative braking operation, is used during powering
of the electric railway vehicle, thereby improving energy efficiency. In this case, a
power conversion device installed on the electric railway vehicle operates as an inverter
for converting power supplied by an overhead line for driving of an electric motor, and a
15 converter for converting regenerative power for supply to the power storage device.
[0003] A driving device of a railway vehicle disclosed in Patent Literature 1 causes
an induction motor to operate as a power generator during regeneration. The alternating
current power generated by the induction motor is converted into direct current power by
an inverter device to charge the power storage device.
20 Citation List
Patent Literature
[0004] Patent Literature 1: Unexamined Japanese Patent Application Publication
No. 2013-211964
Summary of Invention
25 Technical Problem
[0005] In the power conversion device installed on the electric railway vehicle, a
filter capacitor provided on an input side of the power conversion device that is being
3
operated as the inverter has a high voltage comparable to an overhead line voltage.
Under the conditions in which the overhead line voltage differs from a voltage of the
power storage device, and the filter capacitor has a high voltage comparable to the
overhead line voltage, if the power storage device uses regenerative power for charging, a
flow of overcurrent is applied to the power storage device. Providing 5 of a separate
discharging circuit that discharges the filter capacitor for prevention of the overcurrent
complicates the structure of the power conversion device.
[0006] In consideration of the above circumstances, an objective of the present
disclosure is to, without having a complicated structure, prevent a flow of overcurrent in
10 the power storage device during charging of the power storage device by regenerative
power.
Solution to Problem
[0007] In order to attain the above objective, a railway vehicle power conversion
system of the present disclosure includes a power converter, a filter capacitor, a
15 high-speed circuit breaker, an electric path switcher, a power storage device, a
power-storage-device circuit breaker, and a controller. The power converter, having a
primary side and a secondary side, (i) converts power supplied by the primary side and
supplies the converted power to an electric motor connected to the secondary side, or (ii)
converts power supplied from the electric motor and supplies the converted power to the
20 primary side. The filter capacitor is connected to the primary side of the power
converter. The high-speed circuit breaker opens or closes an electric path between a
direct current power source and the power converter. The electric path switcher is
disposed between the high-speed circuit breaker and the power converter, and switches or
opens electric paths between the high-speed circuit breaker and the power converter. A
25 positive terminal of the power storage device is connected to a contact point of the
high-speed circuit breaker and the electric path switcher. A negative terminal of the
power storage device is connected to a negative terminal of the primary side of the power
4
converter. The power-storage-device circuit breaker is disposed between the positive
terminal of the power storage device and a contact point of the high-speed circuit breaker
and the electric path switcher. The controller controls the high-speed circuit breaker, the
electric path switcher, the power-storage-device circuit breaker, and the power converter.
The electric path switcher switches between a first electric path including 5 a resistor and a
second electric path not including a resistor. The controller performs voltage
equilibration control for reducing a voltage of the filter capacitor when a powering
command is no longer input in a state in which the high-speed circuit breaker is closed,
power is supplied to the power converter via the second electric path of the electric path
10 switcher, power-storage-device circuit breaker is open, and the powering command is
being input. During the voltage equilibration control, the controller, after opening the
high-speed circuit breaker, closes the power-storage-device circuit breaker and controls
the electric path switcher and the power converter. The controller controls the electric
path switcher to switch to the second electric path when a difference between the voltage
15 of the filter capacitor and a voltage of the power storage device is less than or equal to a
threshold voltage due to the voltage equilibration control. Upon acquiring a braking
command after switching to the second electric path, the controller, by controlling the
power converter, performs regenerative charging control for supplying the power
supplied from the electric motor to the power storage device via the second electric path.
20 Advantageous Effects of Invention
[0008] According to the present disclosure, a flow of overcurrent in a power storage
device can be prevented during charging of the power storage device by regenerative
power, without having a complicated structure, by performing voltage equilibration
control for reducing the voltage of a filter capacitor when the powering command is no
25 longer input, and performing regenerative charging control for supplying power from the
electric motor to the power storage device upon acquiring of the braking command when
the difference between the voltage of the filter capacitor and the voltage of the power
5
storage device is less than or equal to a threshold voltage.
Brief Description of Drawings
[0009] FIG. 1 is a block diagram illustrating a configuration of a railway vehicle
power conversion system according to Embodiment 1 of the present disclosure;
FIG. 2 is a timing chart indicating operation of voltage 5 equilibration and
regenerative charging performed by the railway vehicle power conversion system
according to Embodiment 1;
FIG. 3 is a diagram illustrating an electric current flow in the railway vehicle
power conversion system according to Embodiment 1;
10 FIG. 4 is a diagram illustrating another electric current flow in the railway vehicle
power conversion system according to Embodiment 1;
FIG. 5 is a diagram illustrating a yet another electric current flow in the railway
vehicle power conversion system according to Embodiment 1;
FIG. 6 is a block diagram illustrating another configuration of the railway vehicle
15 power conversion system according to Embodiment 1;
FIG. 7 is a timing chart indicating operation of voltage equilibration and
regenerative charging performed by the railway vehicle power conversion system
according to Embodiment 1;
FIG. 8 is a diagram illustrating an electric current flow in the railway vehicle
20 power conversion system according to Embodiment 1;
FIG. 9 is a diagram illustrating another electric current flow in the railway vehicle
power conversion system according to Embodiment 1;
FIG. 10 is a flowchart of an example of operation of voltage equilibration and
regenerative charging performed by the railway vehicle power conversion system
25 according to Embodiment 1;
FIG. 11 is a flowchart of another example of the operation of voltage equilibration
and regenerative charging performed by the railway vehicle power conversion system
6
according to Embodiment 1;
FIG. 12 is a timing chart indicating operation of voltage equilibration and
regenerative charging performed by a railway vehicle power conversion system
according to Embodiment 2 of the present disclosure;
FIG. 13 is a diagram illustrating an electric current flow in the 5 railway vehicle
power conversion system according to Embodiment 2;
FIG. 14 is a timing chart indicating operation of voltage equilibration and
regenerative charging performed by the railway vehicle power conversion system
according to Embodiment 2; and
10 FIG. 15 is a diagram illustrating another electric current flow in the railway vehicle
power conversion system according to Embodiment 2.
Description of Embodiments
[0010] A railway vehicle power conversion system according to embodiments of
the present disclosure is hereinafter described with reference to drawings. Note that in
15 the drawings, the same or similar components are denoted by the same reference signs.
[0011] Embodiment 1
A configuration of a railway vehicle power conversion system according to
Embodiment 1 of the present disclosure is described below. As illustrated in FIG. 1, a
railway vehicle power conversion system (hereinafter referred to as power conversion
20 system) 1 includes a power converter 18 that performs bidirectional power conversion.
The power conversion system 1 converts direct current power supplied from a direct
current power source into alternating current power, and supplies the converted
alternating current power to an electric motor 5. In addition, the power conversion
system 1 converts the power supplied from the electric motor 5, and uses the converted
25 power to charge a power storage device 22. The power conversion system 1 is capable
of preventing a flow of overcurrent in the power storage device 22 during charging of the
power storage device 22 by regenerative power generated by regenerative braking
7
operation, without having a complicated structure, by first reducing a voltage of a filter
capacitor 17 provided at a primary side of the power converter 18, and then charging the
power storage device 22.
[0012] The power conversion system 1 is installed, for example, on a railway
vehicle that travels through a direct current electrification section. In 5 an example of FIG.
1, a non-illustrated electricity substation is the direct current power source, and the power
conversion system 1 receives, through a current collector 4, power supplied from the
electricity substation via an overhead line 3. The current collector 4 is, for example, a
pantograph, a third rail, or the like.
10 [0013] The power converter 18 has a primary-side positive terminal connected to
the current collector 4 via a high-speed circuit breaker 11, a reactor 12, and an electric
path switcher 13, and has a grounded primary-side negative terminal. The reactor 12
and the filter capacitor 17 provided at the primary side of the power converter 18
constitute an LC filter. The power converter 18 has a secondary side connected to the
15 electric motor 5. The electric motor 5 is an alternating current electric motor, and
examples of such a motor include an induction motor or a synchronous motor. The
power converter 18 converts power supplied by the primary side, and supplies the
converted power to the electric motor 5 connected to the secondary side. In addition,
the power converter 18 runs the electric motor 5 by supplying power to the electric motor
20 5. The running electric motor 5 powers the railway vehicle having the power
conversion system 1 installed thereon. Furthermore, the power converter 18 converts
the power supplied from the electric motor 5, and supplies the converted power to the
primary side. That is, the power converter 18 converts the power supplied from the
electric motor 5, and supplies the converted power to the primary side.
25 [0014] The power converter 18 includes switching elements TRU1, TRU2, TRV1,
TRV2, TRW1, and TRW2 and reverse current diodes DU1, DU2, DV1, DV2, DW1, and
DW2. In the example of FIG. 1, the power converter 18 includes a U-phase arm, a
8
V-phase arm, and a W-phase arm, and each phase arm is similarly configured. In the
description of the configuration of the power converter 18, the reference signs U, V, and
W of the phase arms are collectively referred to by the reference sign "x". The
switching elements TRx1 and TRx2 are freely-selected semiconductor elements, and in
the example of FIG. 1, the power converter 18 uses insulated gate bipolar 5 transistors
(IGBTs). The switching elements TRx1 and TRx2 may be made of wide bandgap
semiconductors each having a bandgap wider than that of silicon. Examples of the wide
bandgap semiconductor include silicon carbide, gallium nitride-based materials, diamond,
or the like. The switching elements TRx1 and TRx2 made of the wide bandgap
10 semiconductors have high withstand voltage and a high allowable current density
compared to a switching element made of silicon.
[0015] By use of the switching elements TRx1 and TRx2 made of the wide
bandgap semiconductors, the amount of electric current flowing in the electric motor 5
can be large compared with the switching element made of silicon. In addition, use of
15 the wide bandgap semiconductor enables reduction in size of the switching elements
TRx1 and TRx2. Use of such down-sized switching elements TRx1 and TRx2 enables
reduction in size of a semiconductor module incorporating the switching elements TRx1
and TRx2 therein.
[0016] Since the wide bandgap semiconductor has high heat resistance, a reduction
20 in size of radiation fins of a heat sink and changing water cooling to air-cooling can be
achieved, thereby enabling further reduction in size of the semiconductor module.
Furthermore, since the wide bandgap semiconductor has low power loss, which leads to
highly efficient switching elements TRx1 and TRx2, thereby enabling high efficiency in
the semiconductor module.
25 [0017] Series connected switching elements TRx1 and TRx2 are connected in
parallel to the filter capacitor 17. The reverse current diodes Dx1 and Dx2 are
respectively connected in parallel to the switching elements TRx1 and TRx2. The
9
switching elements TRx1 and TRx2 have the contact point thereof that is connected to
the electric motor 5 via a contactor Cx1. In addition, the switching elements TRx1 and
TRx2 have the contact point thereof that is connected at a point between a later-described
power-storage-device contactor 19 and reactor 20 via a contactor Cx2 and a reactor Lx.
[0018] The high-speed circuit breaker 11 opens or closes the electric 5 path between
the direct current power source and the power converter 18. The electric path switcher
13 is located between the high-speed circuit breaker 11 and the power converter 18, and
switches or opens the electric path between the high-speed circuit breaker 11 and the
power converter 18. In particular, the electric path switcher 13 switches between a first
10 electric path including a resistor 16 and a second electric path not including a resistor 16.
In the example of FIG. 1, the electric path switcher 13 includes a line breaker 14 and an
electric path switching contactor 15. In this case, the electric path passing through the
electric path switching contactor 15 and the resistor 16 is the first electric path, and the
electric path passing through the line breaker 14 is the second electric path.
15 [0019] The power conversion system 1 includes the power storage device 22 that is
charged using power supplied from the direct current power source or the electric motor 5.
A rated voltage of the power storage device 22 is less than a voltage of the direct current
power source. The power storage device 22 has a positive terminal connected to the
contact point of the high-speed circuit breaker 11 and the electric path switcher 13 via the
20 power-storage-device contactor 19, the reactor 20, and a power-storage-device circuit
breaker 21. In the example of FIG. 1, the power storage device 22 has the positive
terminal connected to a point between the reactor 12 and the electric path switcher 13 via
the power-storage-device contactor 19, the reactor 20 and the power-storage-device
circuit breaker 21. The power storage device 22 has a negative terminal connected to
25 the primary-side negative terminal of the power converter 18.
[0020] The power conversion system 1 includes a controller 23 for controlling the
high-speed circuit breaker 11, the electric path switcher 13, the power-storage-device
10
circuit breaker 21, and the power converter 18. The controller 23 switches the
high-speed circuit breaker 11 and the power-storage-device circuit breaker 21 between a
closed state and an opened state. In addition, the controller 23 switches the line breaker
14 and the electric path switching contactor 15 that are included in the electric path
switcher 13 between a closed state and an opened state. The controller 5 23 switches the
switching elements TRU1, TRU2, TRV1, TRV2, TRW1, and TRW2 that are included in
the power converter 18 between a closed state and an opened state. The controller 23
switches the contactors CU1, CU2, CV1, CV2, CW1, and CW2 between a closed state
and an opened state. The controller 23 switches the power-storage-device contactor 19
10 between a closed state and an opened state.
[0021] The power conversion system 1 includes a voltage detector V1 that detects a
voltage of the filter capacitor 17, and a voltage detector V2 that detects a voltage of the
power storage device 22. The controller 23 acquires the voltage of the filter capacitor
17 from the voltage detector V1 and acquires the voltage of the power storage device 22
15 from the voltage detector V2.
[0022] The voltage equilibration and the regenerative charging performed by the
power conversion system 1 when braking is being applied after the railway vehicle
travels in a powering operation and then in a coasting operation are described below.
The voltage equilibration reduces the difference between the voltage of the filter
20 capacitor 17 and the voltage of the power storage device 22. The regenerative charging
supplies the power supplied from the electric motor 5 to the power storage device 22 via
the second electric path to charge the power storage device 22. FIG. 2 is a timing chart
indicating the operation of voltage equilibration and regenerative charging performed by
the railway vehicle power conversion system according to Embodiment 1. When the
25 powering state shifts to a coasting state, the voltage equilibration is performed, and
thereafter the regenerative charging is performed. Firstly, control performed by the
controller 23 during the powering is described below. When, for example, at time T1, a
11
master controller of a driver cab is set to powering, and a powering command is input to
the controller 23. Note that a braking command is not input to the controller 23 at time
T1. In FIG. 2, "ON" indicates the input state, and "OFF" indicates the non-input state,
regarding the powering command and the braking command. During the input of the
powering command, the controller 23 maintains the closed state of the 5 high-speed circuit
breaker 11 and the line breaker 14. During the input of the powering command, the
controller 23 maintains the opened state of the electric path switching contactor 15, the
power-storage-device contactor 19, and the power-storage-device circuit breaker 21. In
FIG. 2, "ON" indicates the closed state, and "OFF" indicates the opened state, regarding
10 the high-speed circuit breaker 11, the line breaker 14, the electric path switching
contactor 15, the power-storage-device contactor 19, and the power-storage-device circuit
breaker 21. The voltage difference indicated in FIG. 2 is a difference between the
voltage of the filter capacitor 17 detected by the voltage detector V1 and the voltage of
the power storage device 22 detected by the voltage detector V2. The voltage difference
15 is obtained by subtracting a detected value of the voltage of the power storage device 22
from a detected value of the voltage of the filter capacitor 17. From time T1 to time T2,
since the voltage of the filter capacitor 17 matches an overhead line voltage, the voltage
of the filter capacitor 17 is greater than the voltage of the power storage device 22.
[0023] An electric current flow during the powering is described below. FIG. 3 is
20 a diagram illustrating an electric current flow in the railway vehicle power conversion
system according to Embodiment 1. The electric current flow in the power conversion
system 1 from time T1 to time T2 indicated in FIG. 2 is indicated by thick solid arrows.
The electric current flowing in the power conversion system 1 from the overhead line 3
via the current collector 4 passes through the high-speed circuit breaker 11, the reactor 12,
25 and the line breaker 14, so that the electric current is input to the power converter 18.
The electric current flows from the power converter 18 to the electric motor 5 to drive the
electric motor 5. The power converter 18 controls the electric motor 5 by controlling a
12
magnetic flux component current and a torque component current.
[0024] The voltage equilibration control performed by the controller 23 during the
coasting is described below. At time T2 indicated in FIG. 2, when the powering
command is no longer input, the railway vehicle coasts. That is, the railway vehicle
performs the coasting operation from time T2 to time T4. At 5 time T2, when the
powering command is no longer input, the controller 23 starts the voltage equilibration
control. During the voltage equilibration control, after opening the high-speed circuit
breaker 11, the controller 23 closes the power-storage-device circuit breaker 21, and
controls the electric path switcher 13 and the power converter 18. The above-mentioned
10 control reduces the voltage of the filter capacitor 17.
[0025] During the voltage equilibration control, the controller 23 opens the
high-speed circuit breaker 11 and the electric path switcher 13, that is, opens the
high-speed circuit breaker 11 and the line breaker 14. Thereafter, the controller 23
closes the power-storage-device contactor 19 and the power-storage-device circuit
15 breaker 21. By switching the switching elements TRU1, TRU2, TRV1, TRV2, TRW1,
and TRW2 included in the power converter 18 between the closed state and the opened
state, the controller 23 supplies only excitation current to the electric motor 5 from the
power converter 18. Since only excitation current is supplied to the electric motor 5, the
electric motor 5 is not driven. As described above, performing the voltage equilibration
20 control reduces the voltage of the filter capacitor 17, and reduces the voltage difference
indicated in FIG. 2. After time T3, the voltage difference is less than or equal to the
threshold voltage. When the threshold voltage is set to a value that is sufficiently low,
the voltage of the filter capacitor 17 and the voltage of the power storage device 22, after
time T3, can be regarded as being matched. At time T3, the controller 23 ends the
25 voltage equilibration control. From time T3 to time T4, the electric current does not
flow between the filter capacitor 17 and the power storage device 22.
[0026] An electric current flow during the voltage equilibration control is described
13
below. FIG. 4 is a diagram illustrating an electric current flow in the railway vehicle
power conversion system according to Embodiment 1. The electric current flow in the
power conversion system 1 from time T2 to time T3 indicated in FIG. 2 is indicated by
thick solid arrows. The power converter 18 converts power stored in the filter capacitor
17, and supplies only excitation current to the electric motor 5. The 5 above-mentioned
control reduces the voltage of the filter capacitor 17.
[0027] Control performed by the controller 23 after the voltage equilibration control
is described below. At time T3 indicated in FIG. 2, when the voltage difference is less
than or equal to the threshold voltage, the controller 23 closes the line breaker 14. That
10 is, the controller 23 controls the electric path switcher 13 to switch to the second electric
path. Then, at time T4 indicated in FIG. 2, when, for example, the master controller of a
driver cab is set to braking, the braking command is input to the controller 23. Upon
acquisition of the braking command when the difference between the voltage of the filter
capacitor 17 and the voltage of the power storage device 22 is less than or equal to the
15 threshold voltage, the controller 23 controls the power converter 18 to start the
regenerative charging control for supplying the power supplied from the electric motor 5
to the power storage device 22 via the second electric path. With the above-mentioned
control, the power converted by the power converter 18 is supplied to the power storage
device 22 via the second electric path. That is, the power converter 18 charges the
20 power storage device 22 using the regenerative power.
[0028] The electric current flow in the regenerative charging control is described
below. FIG. 5 is a diagram illustrating the electric current flow in the railway vehicle
power conversion system according to Embodiment 1. The electric current flow in the
power conversion system 1 after time T4 indicated in FIG. 2 is indicated by the thick
25 solid arrows. The power converter 18 converts the power supplied from the electric
motor 5, and supplies the converted power to the power storage device 22 via the line
breaker 14, the power-storage-device contactor 19, the reactor 20, and the
14
power-storage-device circuit breaker 21. The reactor 20 smoothens the electric current
output by the power converter 18.
[0029] According to the power conversion system 1, a flow of the overcurrent in
the power storage device 22 can be prevented because the power storage device 22 is
charged using the regenerative power after reducing the voltage of the filter 5 capacitor 17
to an extent that the voltage of the filter capacitor 17 and the voltage of the power storage
device 22 are regarded as being matched by allowing only the excitation current to flow
to the electric motor 5.
[0030] The controller 23 may acquire the speed of the railway vehicle from, for
10 example, a non-illustrated speed sensor, railway vehicle information management system,
an automatic train control (ATC), and perform the above-mentioned voltage equilibration
control only when the speed of the railway vehicle is greater than or equal to the
threshold speed. For example, the threshold speed is a lower limit value of the speed
range during which the regenerative braking is available, that is to say, is a critical speed.
15 [0031] When the power storage device 22 is charged using power supplied from the
direct current power source, the controller 23 closes the high-speed circuit breaker 11, the
electric path switching contactor 15, contactors CU2, CV2, CW2, and the
power-storage-device circuit breaker 21, and opens the line breaker 14, the
power-storage-device contactor 19, and contactors CU1, CV1, and CW1. Due to the
20 controller 23 controlling the power converter 18, the power converter 18 converts the
power supplied from the direct current power source, and supplies the converted power to
the power storage device 22 via the first electric path. In this case, the reactors LU, LV,
and LW smoothen the electric current output from the power converter 18.
[0032] When the electric motor 5 is driven by the power stored in the power storage
25 device 22, the controller 23 closes the line breaker 14, the power-storage-device contactor
19, the contactors CU1, CV1, and CW1, and the power-storage-device circuit breaker 21,
and opens the high-speed circuit breaker 11, the electric path switching contactor 15, and
15
the contactors CU2, CV2, and CW2. Due to the controller 23 controlling of the power
converter 18, the power converter 18 converts the power supplied from the power storage
device 22, and supplies the converted power to the electric motor 5. In this case, the
electric current flows in the direction opposite to the thick solid arrows illustrated in FIG.
5 5.
[0033] A power conversion system 2 configured differently from the power
conversion system 1 is described below. As illustrated in FIG. 6, the power conversion
system 2 includes an electric path switcher 24 instead of the electric path switcher 13
included in the power conversion system 1 illustrated in FIG. 1. Similarly to the electric
10 path switcher 13, the electric path switcher 24 includes the line breaker 14, the electric
path switching contactor 15, and the resistor 16, although arrangements of these
components differ. The electric path switcher 24 switches between the first electric path
that passes through the line breaker 14 and the resistor 16 and the second electric path
that passes through the line breaker 14 and the electric path switching contactor 15.
15 [0034] The voltage equilibration and the regenerative charging performed by the
power conversion system 2 when braking is being applied after the railway vehicle
travels in a powering operation and then in a coasting operation are described below.
FIG. 7 is a timing chart indicating operation of voltage equilibration and regenerative
charging performed by the railway vehicle power conversion system according to
20 Embodiment 1. FIG. 7 is annotated in a manner similar to FIG. 2. Control performed
by the controller 23 during powering is described below. Similarly to FIG. 2, at time T1,
the powering command is input to the controller 23, while the braking command is not
input to the controller 23. During the input of the powering command, the controller 23
maintains the closed state of the high-speed circuit breaker 11, the line breaker 14, and
25 the electric path switching contactor 15. In addition, during the input of the powering
command, the controller 23 maintains the opened state of the power-storage-device
contactor 19, and the power-storage-device circuit breaker 21.
16
[0035] The electric current flow during the powering is described below. FIG. 8 is
a diagram illustrating the electric current flow in the railway vehicle power conversion
system according to Embodiment 1. The electric current flow in the power conversion
system 2 from time T1 to time T2 indicated in FIG. 7 is indicated by the thick solid
arrows. The electric current flowing in the power conversion 5 system 1 from the
overhead line 3 via the current collector 4 is input to the power converter 18 through the
high-speed circuit breaker 11, the reactor 12, the line breaker 14, and the electric path
switching contactor 15. The electric current flows from the power converter 18 to the
electric motor 5 to drive the electric motor 5. The power converter 18 controls the
10 electric motor 5 by controlling a magnetic flux component current and a torque
component current.
[0036] The voltage equilibration control performed by the controller 23 during the
coasting is described below. At time T2 indicated in FIG. 7, when the powering
command is no longer input, the railway vehicle coasts. At time T2, when the powering
15 command is no longer input, the controller 23 starts the voltage equilibration control.
During the voltage equilibration control, the controller 23 controls the high-speed circuit
breaker 11, the electric path switcher 13, the power-storage-device circuit breaker 21, and
the power converter 18. The above-mentioned control reduces the voltage of the filter
capacitor 17.
20 [0037] During the voltage equilibration control, the controller 23 opens the
high-speed circuit breaker 11, and the electric path switcher 13, that is, opens the
high-speed circuit breaker 11, the line breaker 14, and the electric path switching
contactor 15. Then, similarly to FIG. 2, the controller 23 closes the
power-storage-device contactor 19 and the power-storage-device circuit breaker 21.
25 The controller 23 switches the switching elements TRU1, TRU2, TRV1, TRV2, TRW1,
and TRW2 included in the power converter 18 between the closed state and the opened
state, thereby supplying only excitation current to the electric motor 5 from the power
17
converter 18. Since only excitation current is supplied to the electric motor 5, the
electric motor 5 is not driven. As described above, the voltage equilibration control
reduces the voltage of the filter capacitor 17, and also decreases the voltage difference
indicated in FIG. 7. After time T3, the voltage difference is less than or equal to the
threshold voltage. When the threshold voltage is set to a value that is 5 sufficiently low,
the voltage of the filter capacitor 17 and the voltage of the power storage device 22, after
time T3, can be regarded being matched. At time T3, the controller 23 ends the voltage
equilibration control. From time T3 to time T4, the electric current does not flow
between the filter capacitor 17 and the power storage device 22.
10 [0038] The electric current flow during the voltage equilibration control is
described below. Similarly to the power conversion system 1, the power converter 18
included in the power conversion system 2 converts power stored in the filter capacitor
17 and supplies only excitation current to the electric motor 5 from time T2 to time T3
indicated in FIG. 7, thereby reducing the voltage of the filter capacitor 17.
15 [0039] Control performed by the controller 23 after the voltage equilibration control
is described below. At time T3 indicated in FIG. 7, when the voltage difference is less
than or equal to the threshold voltage, the controller 23 closes the line breaker 14 and the
electric path switching contactor 15. That is, the controller 23 controls the electric path
switcher 13 to switch to the second electric path. Then, at time T4 indicated in FIG. 7,
20 the braking command is input to the controller 23. Upon acquisition of the braking
command when the difference between the voltage of the filter capacitor 17 and the
voltage of the power storage device 22 is less than or equal to the threshold voltage, the
controller 23 controls the power converter 18 to start the regenerative charging control for
supplying the power supplied from the electric motor 5 to the power storage device 22
25 via the second electric path. With the above-mentioned control, the power converted by
the power converter 18 is supplied to the power storage device 22 via the second electric
path. That is, the power converter 18 charges the power storage device 22 using the
18
regenerative power.
[0040] The electric current flow during the regenerative charging control is
described below. FIG. 9 is a diagram illustrating the electric current flow in the railway
vehicle power conversion system according to Embodiment 1. The electric current flow
in the power conversion system 2 after time T4 indicated in FIG. 7 is 5 indicated by thick
solid arrows. The power converter 18 converts the power supplied from the electric
motor 5, and supplies the converted power to the power storage device 22 via the electric
path switching contactor 15, the line breaker 14, the power-storage-device contactor 19,
the reactor 20, and the power-storage-device circuit breaker 21.
10 [0041] Similarly to the power conversion system 1 and according to the power
conversion system 2, the flow of overcurrent in the power storage device 22 can be
prevented because the power storage device 22 is charged using the regenerative power
after reducing the voltage of the filter capacitor 17 to an extent that the voltage of the
filter capacitor 17 and the voltage of the power storage device 22 are regarded as being
15 matched.
[0042] Similarly to the power conversion system 1, the above-described voltage
equilibration control by the controller 23 of the power conversion system 2 is permissible
only when the speed of the railway vehicle is greater than or equal to the threshold speed.
[0043] When the power storage device 22 is charged using the power supplied from
20 the direct current power source, the controller 23 closes the high-speed circuit breaker 11,
the line breaker 14, the contactors CU2, CV2, and CW2, and the power-storage-device
circuit breaker 21, and opens the electric path switching contactor 15, the
power-storage-device contactor 19, and the contactors CU1, CV1, and CW1. Due to the
controller 23 controlling the power converter 18, the power converter 18 converts the
25 power supplied from the direct current power source, and supplies the converted power to
the power storage device 22 via the first electric path. In this case, the reactors LU, LV,
and LW smoothen the electric current output by the power converter 18.
19
[0044] When the electric motor 5 is driven by the power stored in the power storage
device 22, the controller 23 closes the line breaker 14, the electric path switching
contactor 15, the power-storage-device contactor 19, the contactors CU1, CV1, and CW1,
and the power-storage-device circuit breaker 21, and opens the high-speed circuit breaker
11, and the contactors CU2, CV2, and CW2. Due to the controller 5 23 controlling the
power converter 18, the power converter 18 converts the power supplied from the power
storage device 22 and supplies the converted power to the electric motor 5. In this case,
the electric current flows in the direction opposite to the thick solid arrows indicated in
FIG. 9.
10 [0045] FIG. 10 is a flowchart indicating an example of the operation of voltage
equilibration and regenerative charging performed by the railway vehicle power
conversion system according to Embodiment 1. The controller 23 repeats the
processing of step S11, during which the powering command is input (Yes in step S11).
The controller 23 performs voltage equilibration control (step S12) when the powering
15 command is no longer input (No in step S11). When the voltage difference between the
voltage of the filter capacitor 17 and the voltage of the power storage device 22 is not less
than or equal to the threshold voltage (No in step S13), the processing in step S13 is
repeated. When the voltage difference between the voltage of the filter capacitor 17 and
the voltage of the power storage device 22 is less than or equal to the threshold voltage
20 (Yes in step S13), the controller 23 proceeds the processing to the processing of step S14.
The controller 23 controls the electric path switcher 13 to switch to the second electric
path (Step S14). When the braking command is not acquired (No in step S15), the
processing in step S15 is repeated. When the braking command is acquired (Yes in step
S15), the controller 23 performs regenerative charging control (step S16). The
25 controller 23 performs regenerative charging control, for example, until the speed of the
railway vehicle is less than or equal to the critical speed. When the processing in step
S16 is completed, the power conversion systems 1 and 2 end the processing.
20
[0046] FIG. 11 is a flowchart indicating another example of the operation of
voltage equilibration and regenerative charging performed by the railway vehicle power
conversion system according to Embodiment 1. Processing in steps S11 to S16 is the
same as that of FIG. 10. When the powering command is no longer input (No in step
S11) and the speed of the railway vehicle is greater than or equal to the 5 threshold speed
(Yes in step S17), the controller 23 performs voltage equilibration control (step S12).
When the powering command is no longer input (No in step S11) and the speed of the
railway vehicle is less than the threshold speed (No in step S17), the power conversion
systems 1 and 2 end the processing. That is, the power storage device 22 is not charged
10 using the regenerative power.
[0047] As described above, in the power conversion systems 1 and 2 according to
Embodiment 1, the flow of overcurrent in the power storage device 22 can be prevented
because the power storage device 22 is charged using the regenerative power after
reducing the voltage of the filter capacitor 17 to an extent that the voltage of the filter
15 capacitor 17 and the voltage of the power storage device 22 are regarded as being
matched, by allowing only the excitation current to flow to the electric motor 5 from the
power converter 18. Flowing only the excitation current to the electric motor 5 from the
power converter 18 reduces the voltage of the filter capacitor 17, and thus inclusion of a
new circuit for reducing the voltage of the filter capacitor 17 is unnecessary. Thus, the
20 flow of overcurrent in the power storage device 22 can be prevented without
complicating the structure. Switching between the closed state and the opened state of
the switching elements TRU1, TRU2, TRV1, TRV2, TRW1, and TRW2 included in the
power converter 18 is sufficient for reducing the voltage of the filter capacitor 17. Since
there is no need for operation of the high-speed circuit breaker 11, the line breaker 14, the
25 electric path switching contactor 15, the power-storage-device contactor 19, and the
power-storage-device circuit breaker 21, shortening of working life of the equipment due
to repeated closing and opening can be suppressed.
21
[0048] Embodiment 2
Voltage equilibration and regenerative charging performed by the power
conversion system 1 according to Embodiment 2 are described below. The
configuration of a power conversion system 1 according to Embodiment 2 is the same as
that of the power conversion system 1 according to Embodiment 1 illustrated 5 in FIG. 1.
FIG. 12 is a timing chart indicating the operation of voltage equilibration and
regenerative charging performed by the railway vehicle power conversion system
according to Embodiment 2 of the present disclosure. FIG. 12 is annotated in a manner
similar to FIG. 2. Control performed by the controller 23 included in the power
10 conversion system 1 according to Embodiment 2 from time T1 to time T2 is similar to
that of the example of FIG. 2. In addition, the electric current flow in the power
conversion system 1 from time T1 to time T2 is similar to that of the example of FIG. 3.
[0049] At time T2 indicated in FIG. 12, when the powering command is no longer
input, the controller 23 starts the voltage equilibration control for reducing the voltage of
15 the filter capacitor 17 by controlling the high-speed circuit breaker 11, the electric path
switcher 13, the power-storage-device circuit breaker 21, and the power converter 18.
[0050] Voltage equilibration control is described below. During voltage
equilibration control, the controller 23 opens the high-speed circuit breaker 11 and
switches the electric path switcher 13 to the first electric path, that is, the controller 23
20 opens the high-speed circuit breaker 11 and the line breaker 14 and closes the electric
path switching contactor 15. Then, the controller 23 closes the power-storage-device
contactor 19 and the power-storage-device circuit breaker 21. The controller 23 opens
the switching elements TRU1, TRU2, TRV1, TRV2, TRW1, and TRW2 included in the
power converter 18 to stop the power converter 18. Due to such operation, the electric
25 current flows in the power storage device 22 from the filter capacitor 17 via the first
electric path. Performing voltage equilibration control reduces the voltage of the filter
capacitor 17, and also decreases the voltage difference indicated in FIG. 12. After time
22
T3, the voltage difference is less than or equal to the threshold voltage.
[0051] The electric current flow during voltage equilibration control is described
below. FIG. 13 is a diagram illustrating the electric current flow in the railway vehicle
power conversion system according to Embodiment 2. The electric current flow in the
power conversion system 1 from time T2 to time T3 indicated in FIG. 5 12 is indicated by
thick solid arrows. By stopping the power converter 18, the electric current flows in the
power storage device 22 from the filter capacitor 17 via the first electric path, thereby
reducing the voltage of the filter capacitor 17.
[0052] Control performed by the controller 23 after the voltage equilibration control
10 is described below. At time T3 indicated in FIG. 12, when the voltage difference is less
than or equal to the threshold voltage, the controller 23 closes the line breaker 14 and
opens the electric path switching contactor 15. That is, the controller 23 controls the
electric path switcher 13 to switch to the second electric path. Then, at time T4
indicated in FIG. 12, the braking command is input to the controller 23. Upon
15 acquisition of the braking command when the difference between the voltage of the filter
capacitor 17 and the voltage of the power storage device 22 is less than or equal to the
threshold voltage, the controller 23, by controlling the power converter 18, starts the
regenerative charging control for supplying the power supplied from the electric motor 5
to the power storage device 22 via the second electric path. With the above-mentioned
20 control, the power converted by the power converter 18 is supplied to the power storage
device 22 via the second electric path.
[0053] In the power conversion system 1 according to Embodiment 2, the flow of
overcurrent in the power storage device 22 can be prevented because the power storage
device 22 is charged using the regenerative power after reducing the voltage of the filter
25 capacitor 17 to an extent that the voltage of the filter capacitor 17 and the voltage of the
power storage device 22 are regarded as being matched due to the flow of the electric
current to the power storage device 22 from the filter capacitor 17 via the resistor 16.
23
[0054] Similarly to Embodiment 1, the controller 23 may perform the
above-described voltage equilibration control only when the speed of the railway vehicle
is greater than or equal to the threshold speed. The operation performed by the
controller 23 when the power storage device 22 is charged using the power supplied from
the direct current power source and when the electric motor 5 is driven 5 by the power
stored in the power storage device 22 is similar to that of the power conversion system 1
according to Embodiment 1.
[0055] The operation of the power conversion system 2 according to Embodiment
2 performing voltage equilibration and regenerative charging is described below. The
10 configuration of the power conversion system 2 according to Embodiment 2 is similar to
that of the power conversion system 2 according to Embodiment 1 illustrated in FIG. 6.
FIG. 14 is a timing chart indicating the operation of voltage equilibration and
regenerative charging performed by the railway vehicle power conversion system
according to Embodiment 2. FIG. 14 is annotated in a manner similar to that of FIG. 7.
15 Control performed by the controller 23 included in the power conversion system 2
according to Embodiment 2 from time T1 to time T2 is similar to that of FIG. 7. In
addition, the electric current flow in the power conversion system 2 from time T1 to time
T2 is similar to that of the example of FIG. 8.
[0056] When the powering command is no longer input at time T2 indicated in FIG.
20 14, the controller 23 starts the voltage equilibration control for reducing the voltage of the
filter capacitor 17 by controlling the high-speed circuit breaker 11, the electric path
switcher 13, the power-storage-device circuit breaker 21, and the power converter 18.
[0057] During the voltage equilibration control, the controller 23 opens the
high-speed circuit breaker 11 to control the electric path switcher 13 to switch to the first
25 electric path, that is, opens the high-speed circuit breaker 11 and the electric path
switching contactor 15. Then, similarly to FIG. 7, the controller 23 closes the
power-storage-device contactor 19 and the power-storage-device circuit breaker 21.
24
The controller 23 opens the switching elements TRU1, TRU2, TRV1, TRV2, TRW1,
and TRW2 included in the power converter 18 to stop the power converter 18. Due to
such operation, the electric current flows in the power storage device 22 from the filter
capacitor 17 via the first electric path. Performing the voltage equilibration control
reduces the voltage of the filter capacitor 17, and also decreases the 5 voltage difference
indicated in FIG. 14. After time T3, the voltage difference is less than or equal to the
threshold voltage.
[0058] The electric current flow during the voltage equilibration control is
described below. FIG. 15 is a diagram illustrating the electric current flow in the
10 railway vehicle power conversion system according to Embodiment 2. The electric
current flow in the power conversion system 2 from time T2 to time T3 indicated in FIG.
14 is indicated by thick solid arrows. By stopping the power converter 18, the electric
current flows in the power storage device 22 from the filter capacitor 17 via the first
electric path, thereby reducing the voltage of the filter capacitor 17.
15 [0059] Control performed by the controller 23 after the voltage equilibration control
is described below. When the voltage difference is less than or equal to the threshold
voltage at time T3 indicated in FIG. 14, the controller 23 closes the electric path
switching contactor 15. That is, the controller 23 controls the electric path switcher 13
to switch to the second electric path. Then, the braking command is input to the
20 controller 23 at time T4 indicated in FIG. 14. Upon acquisition of the braking command
when the difference between the voltage of the filter capacitor 17 and the voltage of the
power storage device 22 is less than or equal to the threshold voltage, the controller 23,
by controlling the power converter 18, starts the regenerative charging control for
supplying the power supplied from the electric motor 5 to the power storage device 22
25 via the second electric path. With the above-mentioned control, the power converted by
the power converter 18 is supplied to the power storage device 22 via the second electric
path. The electric current flow in the power conversion system 2 after time T4 is similar
25
to that of FIG. 9.
[0060] Similarly to the power conversion system 1 according to Embodiment 2, in
the power conversion system 2 according to Embodiment 2, the flow of overcurrent in
the power storage device 22 can be prevented because the power storage device 22 is
charged using the regenerative power after reducing the voltage of the filter 5 capacitor 17
to an extent that the voltage of the filter capacitor 17 and the voltage of the power storage
device 22 are regarded as being matched due to the flow of the electric current to the
power storage device 22 from the filter capacitor 17 via the resistor 16.
[0061] Similarly to the power conversion system 1, also in the power conversion
10 system 2, performance by the controller 23 of the above-described voltage equilibration
control is permissible only when the speed of the railway vehicle is greater than or equal
to the threshold speed. The operation performed by the controller 23 when the power
storage device 22 is charged using the power supplied from the direct current power
source and when the electric motor 5 is driven by the power stored in the power storage
15 device 22 is similar to that of the power conversion system 2 according to Embodiment 1.
[0062] The operation of regenerative charging performed by the power conversion
systems 1 and 2 according to Embodiment 2 is similar to that of examples of FIGS. 10
and 11.
[0063] As described above, in the power conversion systems 1 and 2 according to
20 Embodiment 2, the flow of the overcurrent in the power storage device 22 can be
prevented because the power storage device 22 is charged using the regenerative power
after reducing the voltage of the filter capacitor 17 to an extent that the voltage of the
filter capacitor 17 and the voltage of the power storage device 22 are regarded as being
matched due to the flow of the electric current to the power storage device 22 from the
25 filter capacitor 17 via the resistor 16. The flow of the electric current flow in the power
storage device 22 from the filter capacitor 17 via the resistor 16 reduces the voltage of the
filter capacitor 17. The resistor 16 is installed beforehand for charging the power
26
storage device 22 using the direct current power source, and thus inclusion of a new
circuit for reducing the voltage of the filter capacitor 17 is unnecessary. Thus, the flow
of overcurrent to the power storage device 22 can be prevented without complicating the
structure.
[0064] Embodiments of the present disclosure are not limited 5 to the foregoing
embodiments. The above-described configurations of the circuits are examples.
[0065] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
persons skilled in the art will recognize that changes may be made in form and detail
10 without departing from the broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative rather than a restrictive
sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of
equivalents to which such claims are entitled.
15 Reference Signs List
[0066] 1, 2 Railway vehicle power conversion system
3 Overhead line
4 Current collector
5 Electric motor
20 11 High-speed circuit breaker
12, 20, LU, LV, LW Reactor
13, 24 Electric path switcher
14 Line breaker
15 Electric path switching contactor
25 16 Resistor
17 Filter capacitor
18 Power converter
27
19 Power-storage-device contactor
21 Power-storage-device circuit breaker
22 Power storage device
23 Controller
CU1, CU2, CV1, CV2, CW1, 5 CW2 Contactor
DU1, DU2, DV1, DV2, DW1, DW2 Reverse current diode
TRU1, TRU2, TRV1, TRV2, TRW1, TRW2 Switching element
V1, V2 Voltage detector
28
We Claim :
1. A railway vehicle power conversion system comprising:
a power converter, having a primary side and a secondary side, to (i) convert
power supplied by the primary side and supply the converted power to an electric motor
connected to the secondary side, or (ii) convert power supplied from 5 the electric motor
and supply the converted power to the primary side;
a filter capacitor connected to the primary side of the power converter;
a high-speed circuit breaker to open or close an electric path between a direct
current power source and the power converter;
10 an electric path switcher, disposed between the high-speed circuit breaker and the
power converter, to switch or open electric paths between the high-speed circuit breaker
and the power converter;
a power storage device having a positive terminal connected to a contact point of
the high-speed circuit breaker and the electric path switcher, and a negative terminal
15 connected to a negative terminal of the primary side of the power converter;
a power-storage-device circuit breaker disposed between the positive terminal of
the power storage device and a contact point of the high-speed circuit breaker and the
electric path switcher; and
a controller to control the high-speed circuit breaker, the electric path switcher, the
20 power-storage-device circuit breaker, and the power converter,
wherein
the electric path switcher switches between a first electric path including a resistor
and a second electric path not including a resistor,
the controller performs voltage equilibration control for reducing a voltage of the
25 filter capacitor when a powering command is no longer input in a state in which the
high-speed circuit breaker is closed, power is supplied to the power converter via the
second electric path of the electric path switcher, the power-storage-device circuit breaker
29
is open, and the powering command is being input,
during the voltage equilibration control, the controller, after opening the
high-speed circuit breaker, closes the power-storage-device circuit breaker and controls
the electric path switcher and the power converter,
the controller controls the electric path switcher to switch to the 5 second electric
path when a difference between the voltage of the filter capacitor and a voltage of the
power storage device is less than or equal to a threshold voltage due to the voltage
equilibration control, and
upon acquiring a braking command after switching to the second electric path, the
10 controller, by controlling the power converter, performs regenerative charging control for
supplying the power supplied from the electric motor to the power storage device via the
second electric path.
2. The railway vehicle power conversion system according to claim 1, wherein
15 during the voltage equilibration control, the controller closes the power-storage-device
circuit breaker after opening the high-speed circuit breaker and the electric path switcher,
and by controlling the power converter, supplies only an excitation current to the electric
motor from the power converter.
20 3. The railway vehicle power conversion system according to claim 1, wherein
during the voltage equilibration control, after opening the high-speed circuit breaker, the
controller closes the power-storage-device circuit breaker, and sends electric current to
the power storage device via the first electric path from the filter capacitor by stopping
operation of the power converter and controlling the electric path switcher to switch to
25 the first electric path.
4. The railway vehicle power conversion system according to any one of
claims 1 to 3, wherein
the controller acquires a speed of a railway vehicle driven by the electric motor,
and
the controller performs the voltage equilibration control when the speed is greater
than or equal to 5 a threshold speed.