1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
POWER CONVERSION DEVICE;
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
Technical Field
[0001] The present disclosure relates to a power conversion device.
5 Background Art
[0002] Some electric railway vehicles are equipped with a power conversion device
that converts, into desired alternating-current power, power supplied from a substation
through an overhead line and that supplies the converted power to a load in a vehicle.
Patent Literature 1 discloses an example of this type of power conversion device. This
10 power conversion device includes (i) two power converters that convert, into
alternating-current power, direct-current power supplied via primary terminals from a
power source to supply the alternating-current power to a load connected to secondary
terminals, and (ii) two filter capacitors connected to the respective primary terminals of
the two power converters and charged with power supplied from the power source.
15 This power conversion device further includes (i) a breaker having a function for
electrically connecting or electrically disconnecting the two power converters to or from
the power source and a function for extinguishing an arc occurring during electrical
disconnection of the power converters from the power source, and (ii) a switch that is
connected to the breaker in series and that electrically connects or electrically disconnects
20 the two power converters to or from the power supply in a state in which the breaker is
closed.
Citation List
Patent Literature
[0003] Patent Literature 1: Unexamined Japanese Patent Application Publication
25 No. 2005–287129
Summary of Invention
Technical Problem
[0004] Dual power converters are used in the power conversion device disclosed in
Patent Literature 1. One of the power converters is set as an operation system, and the
3
other one of the power converters is set as a standby system. Specifically, this power
conversion device controls switching elements of the power converter set as the operation
system to operate the power converter set as the operation system to convert power from
direct-current power to alternating-current power. This power conversion device
includes a breaker to limit current flowing through the power converters. 5 Also, this
power conversion device includes a switch for connecting, to the power supply, either the
power converter set as the operation system or the power converter set as the standby
system.
When a ground fault, a short circuit or the like occurs in an input circuit, that is, a
10 circuit ranging from the breaker to the power converter, or occurs in the power converter,
the power conversion device having the above-described configuration opens the breaker
to stop the power converter. Afterward, this power conversion device switches the
switch from the operation system to the standby system, closes the breaker, and controls
switching elements of the power converter set as a standby system to operate the power
15 converter set as a standby system. Since the breaker provided for the power conversion
device mounted on an electric railway vehicle generally is a large-sized high-voltage
breaker, the power conversion device including the breaker is difficult to be downsized.
Additionally, the power conversion device disclosed in Patent Literature 1 includes
a contactor connected to the primary terminals of the power converters and a contactor
20 connected to the secondary terminals of the power converters, and thus is difficult to
downsize.
[0005] In consideration of the aforementioned circumstances, an objective of the
present disclosure is to downsize a power conversion device using dual power converters,
while ensuring a function for limiting current.
25 Solution to Problem
[0006] In order to attain the aforementioned objective, a power conversion device
according to the present disclosure includes (i) power conversion units connected in
common to a power source and (ii) a contactor controller.
Each of the power conversion units includes a fuse, a power converter, and a first
4
contactor. The fuse cuts off an electrical path when direct current supplied from the
power source becomes greater than or equal to a threshold. The power converter has
primary terminals and secondary terminals and converts, into power to be supplied to a
load connected to the secondary terminals, direct-current power supplied from the power
source via the primary terminals, and supplies the converted power to 5 the load from the
secondary terminals. The first contactor electrically connects or electrically disconnects
the power converters to or from the power source. When the direct current becomes
greater than or equal to the threshold, the fuse melts to cut off the electrical path, thereby
electrically disconnecting, from the power source, the power converter provided for the
10 power conversion unit including the fuse. The contactor controller closes or opens the
first contactor of each of the power conversion units.
Advantageous Effects of Invention
[0007] The power conversion device according to the present disclosure includes
the multiple power conversion units each including the power converter, thereby using
15 dual power converters. Also, since each of the power conversion units includes the fuse,
the power conversion device can be downsized while the function for limiting current is
ensured.
Brief Description of Drawings
[0008] FIG. 1 is a block diagram of a power conversion device according to
20 Embodiment 1 of the present disclosure;
FIG. 2 is a drawing illustrating a filter reactor according to Embodiment 2 of the
present disclosure; and
FIG. 3 is a block diagram of a power conversion device according to an
embodiment of the present disclosure.
25 Description of Embodiments
[0009] Power conversion devices according to embodiments of the present
disclosure are described below in detail with reference to drawings. In the drawings,
components that are the same or equivalent are assigned the same reference sign.
[0010] Embodiment 1
5
A power conversion device mounted on a direct current-feeding type electric
railway vehicle is described in Embodiment 1. As illustrated in FIG. 1, a current
collector 4 mounted on an electric railway vehicle acquires direct-current power from a
substation, that is a direct-current power source, via an overhead line 3, and supplies the
power to the power conversion device 1 according to Embodiment 1. In 5 order to supply
power to a load 7 mounted on the electric railway vehicle, the power conversion device 1
converts the supplied direct-current power into three-phase alternating-current power.
The power conversion device 1 supplies the three-phase alternating-current power to the
load 7 via a transformer 5 and alternating-current filter capacitors 6.
10 [0011] The primary terminals of the transformer 5 are connected to the respective
output terminals of the power conversion device 1, specifically, the respective secondary
terminals of a switch 12, which is described below. Also, the secondary terminals of the
transformer 5 are each connected to the load 7. The transformer 5 converts, into desired
alternating-current power, the three-phase alternating-current power input via the primary
15 terminals, and supplies the converted alternating-current power to the load 7 from the
secondary terminals.
The alternating-current filter capacitors 6 are connected to each of the secondary
terminals of the transformer 5 and reduce harmonic components included in an output of
the power conversion device 1.
20 [0012] The power conversion device 1 includes (i) power conversion units 10 and
20 that each convert, into three-phase alternating-current power, the direct-current power
supplied from the current collector 4 and that supply the three-phase alternating-current
power to the load 7, and (ii) the switch 12 that electrically connects one of the power
conversion units 10 and 20 to the load 7. The dual power conversion units 10 and 20
25 are connected in common to the current collector 4 and also connected in common to the
switch 12. One of the power conversion units 10 and 20 is set as an operation system
and the other one of the power conversion units 10 and 20 is set as a standby system.
[0013] While the power conversion unit 10 set as the operation system converts,
into the three-phase alternating-current power, the direct-current power supplied from the
6
current collector 4 and supplies the three-phase alternating-current power to the load 7,
the power conversion unit 20 set as a standby system is stopped. Also, when the power
conversion unit 10 set as the operation system is stopped, the power conversion unit 20
set as a standby system converts, into three-phase alternating-current power, the
direct-current power supplied from the current collector 4, and supplies 5 the three-phase
alternating-current power to the load 7.
[0014] The primary terminals of the switch 12 are connected to the respective
output ends of the power conversion units 10 and 20, specifically, the respective
secondary terminals of below-described power converters 11 and 21. Also, the
10 secondary terminals of the switch 12 are each connected to the transformer 5. The
switch 12 is controlled by a contactor controller 31, which is described below, to
electrically connect (i) the primary terminals connected to the power converter 11 and the
respective secondary terminals, or (ii) the primary terminals connected to the power
converter 21 and the respective secondary terminals.
15 [0015] The power conversion unit 10 includes (i) a fuse F1 having one end
connected to the current collector 4, (ii) a first contactor MC11 having one end connected
to the other end of the fuse F1, (iii) a filter reactor FL1 having one end connected to the
other end of the first contactor MC11, and (iv) a filter capacitor FC1 having one end
connected to the other end of the filter reactor FL1 and having the other end grounded.
20 The power conversion unit 10 further includes the power converter 11 including
primary terminals between which the filter capacitor FC1 is connected. The secondary
terminals of the power converter 11 are connected to the switch 12.
[0016] The configuration of the power conversion unit 20 is similar to that of the
power conversion unit 10. Specifically, the power conversion unit 20 includes (i) a fuse
25 F2 having one end connected to the current collector 4, (ii) a first contactor MC21 having
one end connected to the other end of the fuse F2, (iii) a filter reactor FL2 having one end
connected to the other end of the first contactor MC21, and (iv) a filter capacitor FC2
having one end connected to the other end of the filter reactor FL2 and having the other
end grounded.
7
The power conversion unit 20 further includes the power converter 21 including
primary terminals between which the filter capacitor FC2 is connected. The secondary
terminals of the power converter 21 are connected to the switch 12.
[0017] The power conversion device 1 further includes (i) the contactor controller
31 that closes or opens the first contactor MC11 provided for the power 5 conversion unit
10 and the first contactor MC21 provided for the power conversion unit 20 to switch the
switch 12 to the operation system or the standby system, (ii) a switching controller 32 that
controls switching elements of the power converters 11 and 21, and (iii) a failure
determiner 33 that determines the presence or absence of failure of each of the power
10 conversion units 10 and 20.
[0018] Each component of the power conversion unit 10 is described.
When the direct-current supplied from the current collector 4 becomes greater than
or equal to a threshold, that is, when an overcurrent occurs, the fuse F1 melts to cut off
the electrical path. As a result, the power converter 11 is electrically disconnected from
15 the current collector 4. This threshold is set so as to prevent overcurrent from occurring
in the overhead line 3 and to prevent a non-illustrated breaker of the substation from
tripping. The length of a conductor forming the fuse F1, the thickness of the conductor,
a material of the conductor, and the like are determined in accordance with this threshold.
[0019] The first contactor MC11 includes a direct-current electromagnetic
20 contactor. Also, the first contactor MC11 is controlled by the contactor controller 31.
One end of the first contactor MC11 is connected to the other end of the fuse F1, and the
other end of the first contactor MC11 is connected to one end of the filter reactor FL1.
When the contactor controller 31 closes the first contactor MC11, one end and the
other end of the first contactor MC11 are connected to each other, so that the fuse F1 and
25 the filter reactor FL1 are electrically connected to each other. As a result, the power
converter 11 is electrically connected to the current collector 4.
Also, when the contactor controller 31 opens the first contactor MC11, one end
and the other end of the first contactor MC11 are insulated from each other, so that the
filter reactor FL1 is electrically disconnected from the fuse F1. As a result, the power
8
converter 11 is electrically disconnected from the current collector 4.
[0020] One end of the filter reactor FL1 is connected to the other end of the first
contactor MC11, and the other end of the filter reactor FL1 is connected to one end of the
filter capacitor FC1 and a primary terminal of the power converter 11. The filter reactor
FL1 reduces harmonic components included 5 in input current.
One end of the filter capacitor FC1 is connected to the other end of the filter
reactor FL1, and the other end of the filter capacitor FC1 is grounded. Also, the filter
capacitor FC1 is connected between the primary terminals of the power converter 11 and
is charged with the direct-current power supplied from the current collector 4. The filter
10 capacitor FC1 smooths voltage. Also, the filter reactor FL1 and the filter capacitor FC1
form an LC filter, thereby reducing noise generated during operation, which is described
below, of the power converter 11 and a noise component included in input current from
the overhead line 3.
[0021] The power converter 11 converts, into three-phase alternating-current power,
15 the direct-current power supplied from the current collector 4 through the primary
terminals, and supplies the three-phase alternating-current power to the load 7 via the
switch 12 connected to each secondary terminal, the transformer 5 and the
alternating-current filter capacitors 6. Specifically, the switching elements provided for
the power converter 11 are controlled by the switching controller 32, so that the power
20 converter 11 converts the direct-current power into the three-phase alternating-current
power and supplies the three-phase alternating-current power to the load 7.
The power converter 11 includes, for example, a constant voltage constant
frequency (CVCF) inverter.
[0022] Each component of the power conversion unit 20 is described. The
25 configuration of the power conversion unit 20 is similar to that of the power conversion
unit 10.
When the direct current supplied from the current collector 4 becomes greater than
or equal to a threshold, the fuse F2 melts to cut off the electrical path. As a result, the
power converter 21 is electrically disconnected from the current collector 4. This
9
threshold is set similarly to the case of the fuse F1. The length of a conductor forming
the fuse F2, the thickness of the conductor, the material of the conductor, and the like are
determined in accordance with this threshold.
[0023] The first contactor MC21 includes a direct-current electromagnetic
contactor. Also, the first contactor MC21 is controlled by the contactor 5 controller 31.
One end of the first contactor MC21 is connected to the other end of the fuse F2, and the
other end of the first contactor MC21 is connected to one end of the filter reactor FL2.
When the contactor controller 31 closes the first contactor MC21, one end and the
other end of the first contactor MC21 are connected to each other, so that the fuse F2 and
10 the filter reactor FL2 are electrically connected to each other. As a result, the power
converter 21 is electrically connected to the current collector 4.
Also, when the contactor controller 31 opens the first contactor MC21, one end
and the other end of the first contactor MC21 are insulated from each other, so that the
filter reactor FL2 is electrically disconnected from the fuse F2. As a result, the power
15 converter 21 is electrically disconnected from the current collector 4.
[0024] One end of the filter reactor FL2 is connected to the other end of the first
contactor MC21, and the other end of the filter reactor FL2 is connected to one end of the
filter capacitor FC2 and the primary terminal of the power converters 21. The filter
reactor FL2 reduces harmonic components included in the input current.
20 One end of the filter capacitor FC2 is connected to the other end of the filter
reactor FL2, and the other end of the filter capacitor FC2 is grounded. Also, the filter
capacitor FC2 is connected between the primary terminals of the power converter 21 and
is charged with the direct-current power supplied from the current collector 4. The filter
capacitor FC2 smooths voltage. Also, since the filter reactor FL2 and the filter capacitor
25 FC2 form an LC filter, noise generated during operation, which is described below, of the
power converter 21 is reduced, and a noise component included in the input current from
the overhead line 3 is reduced.
[0025] The power converter 21 converts, into three-phase alternating-current power,
the direct-current power supplied from the current collector 4 via the primary terminals,
10
and supplies the three-phase alternating-current power to the load 7 via the switch 12
connected to each secondary terminal, the transformer 5 and the alternating-current filter
capacitors 6. Specifically, the switching elements provided for the power converter 21
are controlled by the switching controller 32, so that the power converter 21 converts the
direct-current power into the three-phase alternating-current power, 5 and supplies the
three-phase alternating-current power to the load 7.
The power converter 21 includes, for example, a CVCF inverter.
[0026] The contactor controller 31, the switching controller 32, and the failure
determiner 33 are described that control the power conversion units 10 and 20 having the
10 above-described configurations and enable switching between the operation system and
the standby system.
The contactor controller 31 closes or opens the first contactors MC11 and MC21,
and switches the switch 12 to the operation system or the standby system. An operation
instruction signal for instruction to start or stop the power conversion device 1 is supplied
15 to the contactor controller 31 from a non-illustrated cab. Also, the contactor controller
31 holds beforehand information about which of the power conversion units 10 and 20 is
taken to be the operation system. Additionally, the contactor controller 31 is supplied,
from the failure determiner 33, with a failure determination signal S2 indicating the
presence or absence of failure of the power conversion units 10 and 20.
20 [0027] Specifically, upon being supplied with the operation instruction signal for
instruction to start the power conversion device 1 in a state in which the first contactor
MC11 is opened, the contactor controller 31 closes the first contactor MC11 and further
switches the switch 12 to the operation system. The contactor controller 31 keeps the
first contactor MC21 open. The contactor controller 31 supplies the switching
25 controller 32 and the failure determiner 33 with a contactor state signal S1 indicating that
the first contactor MC11 is closed.
Also, upon being supplied the operation instruction signal for instruction to stop
the power conversion device 1, the contactor controller 31 opens the first contactor MC11
that is closed.
11
[0028] Additionally, in a case in which the failure determination signal S2
indicating occurrence of failure is supplied in a state in which the first contactor MC11 is
closed and the switch 12 is switched to the operation system, the contactor controller 31
opens the first contactor MC11 and switches the switch 12 to the standby system. Next,
the contactor controller 31 closes the first contactor MC21. The contactor 5 controller 31
supplies the switching controller 32 and the failure determiner 33 with the contactor state
signal S1 indicating that the first contactor MC21 is closed.
[0029] The switching controller 32 controls the switching elements provided for the
power converters 11 and 21 in accordance with the contactor state signal S1.
10 Specifically, when the contactor state signal S1 indicates that the first contactor
MC11 is closed, the switching controller 32 transmits, as described below, switching
control signals to the switching elements provided for the power converter 11 provided
for the power conversion unit 10 including the closed first contactor MC11, to control the
switching elements. In this case, the switching controller 32 transmits, to the power
15 converter 21, switching control signals for turning off the switching elements provided
for the power converter 21.
Also, when the contactor state signal S1 indicates that the first contactor MC21 is
closed, the switching controller 32 transmits, as described below, switching control
signals to the switching elements provided for the power converter 21 to control the
20 switching elements. In this case, the switching controller 32 transmits, to the power
converter 11, switching control signals for turning off the switching elements provided
for the power converter 11.
[0030] Also, the switching controller 32 is supplied, from the below-described
failure determiner 33, with a failure determination signal S2 indicating the presence or
25 absence of failure of the power conversion unit 10 or 20.
Upon being supplied with the failure determination signal S2 indicating occurrence
of failure when the contactor state signal S1 is supplied that indicates that the first
contactor MC11 is closed, the switching controller 32 transmits, to the power converter
11, the switching control signals for turning off the switching elements provided for the
12
power converter 11.
Also, upon being supplied with the failure determination signal S2 indicating
occurrence of failure when the contactor state signal S1 is supplied that indicates that the
first contactor MC21 is closed, the switching controller 32 transmits, to the power
converter 21, the switching control signals for turning off the 5 switching elements
provided for the power converter 21.
[0031] The contactor state signal S1 is supplied from the contactor controller 31 to
the failure determiner 33. Upon acquiring the contactor state signal S1 indicating that
the first contactor MC11 or MC21 is closed, the failure determiner 33 starts processing
10 for determining the presence or absence of failure of the power conversion unit 10 or 20.
When the first contactor MC11 is closed, the failure determiner 33 determines the
presence or absence of failure of the power conversion unit 10, based on (i) the switching
control signals sent to the power converter 11, (ii) feedback signals each indicating a state
of the corresponding switching element provided for the power converter 11, (iii) output
15 voltage or output current of the power converter 11, (iv) the presence or absence of
melting of the fuse F1, (v) input voltage or input current of the power converter 11, (vi)
output voltage or output current to the load 7, or the like. Similarly, when the first
contactor MC21 is closed, the failure determiner 33 determines the presence or absence
of failure of the power conversion unit 20, based on (i) the switching control signals sent
20 to the power converter 21, (ii) feedback signals each indicating a state of the
corresponding switching element provided for the power converter 21, (iii) output voltage
or output current of the power converter 21, (iv) the presence or absence of melting of the
fuse F2, (v) input voltage or input current of the power converter 21, (vi) the output
voltage or output current to the load 7, and the like.
25 [0032] Processing for determining the presence or absence of failure of the power
conversion units 10 and 20 that is performed by the failure determiner 33 is described by
taking, as an example, processing for determining the presence or absence of failure using
the switching control signals and the feedback signals.
The failure determiner 33 acquires, from the switching controller 32, the switching
13
control signals sent to the power converter 11 or 21. Also, the failure determiner 33
acquires, from the power converter 11 or 21, the feedback signals each indicating the
on/off state of the corresponding switching element. The failure determiner 33
determines whether the on/off state of the switching element indicated by the switching
control signal matches the on/off state of the switching element indicated 5 by the feedback
signal. When the on/off state of the switching element indicated by the switching
control signal does not match the on/off state of the switching element indicated by the
feedback signal, failure of the power conversion unit 10 or 20 can be deemed to be
occurring. Upon determining that the on/off state of the switching element indicated by
10 the switching control signal does not match the on/off state of the switching element
indicated by the feedback signal, the failure determiner 33 supplies the high-level failure
determination signal S2 to the contactor controller 31.
[0033] Next, operation of the power conversion device 1 having the
above-described configuration is described. First, a case is described as an example in
15 which failure of the power conversion unit 10 and the power conversion unit 20 is not
currently occurred.
When a raising switch is operated for raising a pantograph that is an example of the
current collector 4 at the start of operation of the electric railway vehicle so that the
current collector 4 comes into contact with the overhead line 3, the current collector 4 is
20 supplied with power from the substation. Also, in conjunction with the operation of the
pantograph raising switch, the operation instruction signal for instruction to start the
power conversion device 1 is supplied to the contactor controller 31 from the cab. Upon
being supplied with the operation instruction signal for instruction to start the power
conversion device 1, the contactor controller 31 switches the switch 12 to the operation
25 system and then closes the first contactor MC11.
[0034] When the first contactor MC11 is closed as described above, the power
acquired by the current collector 4 from the substation via the overhead line 3 is supplied
to the filter capacitor FC1 via the fuse F1, the first contactor MC11 and the filter reactor
FL1, and charging of the filter capacitor FC1 starts.
14
[0035] Also, when the contactor controller 31 switches the switch 12 to the
operation system as described above, the primary terminals of the switch 12 connected to
the power converter 11 are connected to the respective secondary terminals, thereby
electrically connecting the power converter 11 and the load 7. Switching the switch 12
to the operation system is assumed to include maintaining the state in which 5 the switch 12
is switched to the operation system.
[0036] Afterward, when the charging of the filter capacitor FC1 is completed and
inter-terminal voltage of the filter capacitor FC1 becomes higher than or equal to
threshold voltage, the switching controller 32 controls the switching elements of the
10 power converter 11 to cause the power converter 11 to convert, into three-phase
alternating-current power to be supplied to the load 7, the direct-current power supplied
via the primary terminals. The switching elements are controlled such that the voltage
and the frequency of the three-phase alternating-current power are kept constant.
[0037] Specifically, the switching controller 32 acquires a current value of each
15 phase from a current measurer connected to the secondary terminals of the power
converter 11. Also, the switching controller 32 acquires the output voltage of the power
converter 11 from a non-illustrated voltage measurer connected to the secondary
terminals of the power converter 11. The switching controller 32 transmits the
switching control signals to the switching elements of the power converter 11 to control
20 the switching elements so that the output voltage and the frequency of the output voltage
are kept constant.
[0038] Next, operation of the power conversion device 1 for switching from the
operation system to the standby system is described by taking as an example a case in
which the failure of the power conversion unit 10 occurs while the switching controller
25 32 controls the power converter 11 as described above in order to supply power to the
load 7.
Upon acquiring the contactor state signal S1 indicating that the first contactor
MC11 is closed, the failure determiner 33 starts processing for determining the presence
or absence of the failure of the power conversion unit 10. Specifically, the failure
15
determiner 33 determines whether the on/off state of the switching element indicated by
the switching control signal matches the on/off state of the switching element indicated
by the feedback signal. When the on/off state of the switching element indicated by the
switching control signal does not match the on/off state of the switching element
indicated by the feedback signal, the failure of the power conversion 5 unit 10 can be
deemed to be occurring. Upon determining that the on/off state of the switching
element indicated by the switching control signal does not match the on/off state of the
switching element indicated by the feedback signal, the failure determiner 33 supplies the
high-level failure determination signals S2 to the contactor controller 31 and the
10 switching controller 32.
[0039] Upon being supplied with the high-level failure determination signal S2
when the contactor state signal S1 is supplied that indicates that the first contactor MC11
is closed, the switching controller 32 transmits, to the power converter 11, the switching
control signals for turning off the switching elements provided for the power converter 11.
15 As a result, the switching elements provided for the power converter 11 are turned off,
and the power converter 11 is stopped.
[0040] The contactor controller 31 opens the first contactor MC11 when the
high-level failure determination signal S2 is being supplied while the first contactor
MC11 is closed. Afterward, the contactor controller 31 switches the switch 12 to the
20 standby system and then closes the first contactor MC21. The contactor controller 31
supplies, to the switching controller 32 and the failure determiner 33, the contactor state
signal S1 indicating that the first contactor MC21 is closed.
[0041] When the contactor controller 31 switches the switch 12 to the standby
system as described above, the primary terminals of the switch 12 are connected to the
25 respective secondary terminals of the power converter 21, and the power converter 21
and the load 7 are electrically connected to each other. Switching the switch 12 to the
standby system is assumed to include maintaining the state in which the switch 12 is
switched to the standby system.
[0042] Upon being supplied with the contactor state signal S1 indicating that the
16
first contactor MC21 is closed, the switching controller 32 controls the switching
elements of the power converter 21 to cause the power converter 21 to convert, into the
three-phase alternating-current power to be supplied to the load 7, the direct-current
power supplied via the primary terminals. As a result, even when the failure of the
power conversion unit 10 occurs, power is continuously supplied to the 5 load 7 by causing
operation of the power conversion unit 20.
[0043] When the failure of the power conversion unit 10 occurs as described above
so that the direct current supplied from the current collector 4 becomes greater than or
equal to the threshold, the fuse F1 melts to cut off the electrical path. As a result, the
10 power converter 11 is electrically disconnected from the current collector 4.
[0044] As described above, the power conversion device 1 according to the
embodiment of the present disclosure includes the power conversion units 10 and 20 that
each convert supplied direct-current power into alternating-current power to supply the
alternating-current power to the load 7. Provision of the power conversion units 10 and
15 20 enables power to be continuously supplied to the load 7 by operating one of the power
conversion units 10 and 20 even when failure of the other occurs. Also, the power
conversion units 10 and 20 include respectively the fuses F1 and F2 in order to cut off the
electrical path when an overcurrent occurs. Since the fuses F1 and F2 are each smaller
in size than a breaker, the power conversion device 1 can be downsized to be smaller than
20 the conventional power conversion device that includes a breaker. Also, although the
breaker is large in size and is hard to house in the same housing as other components of
the power conversion device, the fuses F1 and F2 can be housed in the same housing as
that of other components of the power conversion device 1.
[0045] Embodiment 2
25 The power conversion units 10 and 20 are connected in common to the current
collector 4 and are connected in common to the load 7. In other words, when the power
conversion device 1 is a standby-dual-system power conversion device, the power
conversion device 1 can be further downsized by the filter reactors FL1 and the FL2
sharing an iron core. A configuration in which filter reactors FL1 and FL2 share an iron
17
core is described as Embodiment 2.
[0046] Basic configuration and operation of a power conversion device 1 according
to Embodiment 2 are similar to those of Embodiment 1. Structures of filter reactors FL1
and FL2 different from those of Embodiment 1 are described with reference to FIG. 2.
The filter reactors FL1 and FL2 share 5 an iron core 40.
The filter reactor FL1 includes a coil 41 wound around the iron core 40. One end
41a of the coil 41 is connected to the other end of the first contactor MC11. The other
end 41b of the coil 41 is connected to one end of the filter capacitor FC1 and a primary
terminal of the power converter 11.
10 The filter reactor FL2 includes a coil 42 wound around the iron core 40. One end
42a of the coil 42 is connected to the other end of the first contactor MC21. The other
end 42b of the coil 42 is connected to one end of the filter capacitor FC2 and a primary
terminal of the power converter 21.
[0047] As described above, according to the power conversion device according to
15 Embodiment 2 of the present disclosure, the filter reactors FL1 and FL2 share the iron
core 40. The filter reactors FL1 and FL2 including the iron core 40 can be downsized as
compared with filter reactors having no iron core. Also, since the filter reactors FL1 and
FL2 share the iron core 40, the power conversion device 1 according to Embodiment 2
can be downsized to be smaller than power conversion devices each including filter
20 reactors individually including an iron core.
In the standby-dual-system power conversion device 1, since current flows through
only one of the coils 41 and 42, consideration of the magnetic circuit formed by just one
of the coils 41 and 42 is sufficient during design of the iron core 40. As a result, an iron
core having the same size as in the case where each of the coils 41 and 42 includes an
25 individual iron core can be used as the shared iron core 40.
[0048] Embodiments of the present disclosure are not limited to the
above-described examples.
The circuit configuration described above is an example, and a modified example
of the power conversion device is illustrated in FIG. 3. The power conversion device 2
18
illustrated in FIG. 3 further includes a series circuit of a second contactor MC12 and a
resistor R1 that is connected in parallel to the first contactor MC11. Also, the power
conversion device 2 further includes a series circuit of the second contactor MC22 and a
resistor R2 that is connected in parallel to the first contactor MC21.
[0049] The contactor controller 31 provided for the power conversion 5 device 2
closes the second contactor MC12 before the first contactor MC11 is closed, and closes
the first contactor MC11 after the filter capacitor FC1 is charged. Since the resistor R1
is connected in series to the second contactor MC12, inrush current is prevented from
flowing to the filter capacitor FC1 when the second contactor MC12 is closed.
10 Similarly, the contactor controller 31 closes the second contactor MC22 before the
first contactor MC21 is closed, and closes the first contactor MC21 after the filter
capacitor FC2 is charged. Since the resistor R2 is connected in series to the second
contactor MC22, inrush current is prevented from flowing to the filter capacitor FC2
when the second contactor MC22 is closed.
15 [0050] Each of the power conversion devices 1 and 2 may further include (i) a
backflow prevention diode that has an anode connected to the other end of the filter
reactor FL1 and a cathode connected to one end of the filter capacitor FC1, and (ii) a
backflow prevention diode that has an anode connected to the other end of the filter
reactor FL2 and a cathode connected to one end of the filter capacitor FC2.
20 [0051] Also, each of the power conversion devices 1 and 2 may further include (i) a
thyristor that has an anode connected to the other end of the filter reactor FL1 and a
cathode connected to one end of the filter capacitor FC1, (ii) a thyristor that has an anode
connected to the other end of the filter reactor FL2 and a cathode connected to one end of
the filter capacitor FC2, and (iii) resistors connected in parallel to the respective
25 thyristors.
[0052] The number of power conversion units is not limited to two and is a
freely-selected number greater than or equal to two. For example, in a case in which the
power conversion device 1 includes three power conversion units and a switch that has
primary terminals connected to the three power conversion units and secondary terminals
19
connected to the transformer 5, upon being supplied with the operation instruction signal
for instruction to start the power conversion device 1, the contactor controller 31 closes a
first contactor provided for a power conversion unit set as an operation system, and opens
first contactors provided for the other two power conversion units set as a standby system.
Also, the contactor controller 31 switches the switch to the 5 operation system.
[0053] Also, switching between the power conversion units 10 and 20 is not limited
to occurring when failure occurs. As an example, switching between the power
conversion units 10 and 20 for operation may be performed in a predetermined cycle.
Specifically, the contactor controller 31 may repeatedly perform switching between the
10 operation system and the standby system in the predetermined cycle. As a result, the
usage times of the power conversion units 10 and 20 are maintained at the same level,
which suppresses deterioration of only one of the power conversion units 10 and 20. In
this case, the use of the failure determiner 33 for the power conversion devices 1 and 2 is
optional.
15 [0054] Each of the power conversion units 10 and 20 may be connected to an
independent load 7. In this case, the power conversion device 1 does not include the
switch 12, and the secondary terminals of each of the power converters 11 and 21 are to
be connected to the independent load 7 via an independent transformer 5 and independent
alternating-current filter capacitors 6.
20 [0055] The power conversion devices 1 and 2 may be mounted on an electric
railway vehicle in which the current collector 4 that is a current collecting shoe acquires
power from a third rail. Also, the power conversion devices 1 and 2 may include a
contactor instead of the switch 12.
[0056] The power conversion unit 10 or 20 to be set as the operation system is
25 freely selected. For example, the power conversion unit 20 may be set as an operation
system, and the power conversion unit 10 may be set as a standby system. In this case,
the contactor controller 31 is to close the first contactor MC21 upon being supplied with
the operation instruction signal for instruction to start the power conversion device 1.
The contactor controller 31 is further to switch the switch 12 to the operation system.
20
Also, the contactor controller 31 is to keep the first contactor MC11 open.
[0057] The trigger for starting the power conversion device 1 is not limited to the
operation instruction signal. As an example, the contactor controller 31 may close the
first contactor MC11 when the current collector 4 comes into contact with the overhead
line 3. Specifically, the contactor controller 31 may (i) acquire 5 a measured voltage
value from a voltage measurer that measures voltage between one end of the first
contactor MC11 and the other end of the filter capacitor FC1 that corresponds to voltage
of the overhead line 3 and (ii) close the first contactor MC11 and the switch 12 when the
measured voltage value becomes higher than or equal to a threshold voltage. This
10 threshold voltage is separately set in consideration of the possible minimum value of the
voltage of the overhead line 3.
[0058] Configurations of the power converters 11 and 21 are freely selected as long
as such configurations each include a switching element, and enables the power
converters 11 and 21 to convert, by on/off operation of the switching element, the
15 supplied direct-current power into power to be supplied to the load 7. The power
converters 11 and 21 may be variable voltage variable frequency (VVVF) inverters or
direct current-direct current (DC-DC) converters that supply power to the electric motor.
When the power converters 11 and 21 are DC-DC converters, secondary terminals of
each of the DC-DC converters are to be connected to the load 7, and a filter capacitor is to
20 be provided between the secondary terminals.
[0059] The method of failure determination by the failure determiner 33 is not
limited to the above-described examples, and the failure determination method is freely
selected as long as such method enables determination as to the presence or absence of
the failure of the power conversion unit 10 or 20. As an example, the failure determiner
25 33 may determine, based on the presence or absence of melting of the fuses F1 and F2,
the presence or absence of the failure of the power conversion unit 10 or 20.
Specifically, the failure determiner 33 may acquire, from melting detection switches
mounted on the fuses F1 and F2, signals indicating the presence or absence of melting of
the fuses to determine, based on these signals, the presence or absence of melting of the
21
fuses F1 and F2. Upon determining that the fuses F1 and F2 are melted, the failure
determiner 33 may supply the high-level failure determination signal S2 to the contactor
controller 31 and the switching controller 32. Since subsequent processes are the same
as those of the above-described embodiment, when overcurrent occurs and the fuse F1
melts, the power conversion unit 10 set as the operation system is stopped, 5 and the power
conversion unit 20 set as the standby system operates. When the melted fuse F1 is
replaced, power conversion processing by the power conversion unit 10 becomes
possible again.
As another example, the failure determiner 33 may (i) monitor a temperature of a
10 cooling unit for semiconductors provided for the power converters 11 and 21 and (ii)
determine, when the temperature is greater than or equal to a specified value, that the
failure of the power converters 11 and 21 occurs.
[0060] As yet another example, the failure determiner 33 may determine whether
the amplitude of each phase current is less than or equal to a first amplitude or is greater
15 than or equal to a second amplitude greater than the first amplitude. The first amplitude
is, for example, one-half of the amplitude of each phase current in a case in which failure
of the power conversion units 10 and 20 is not currently occurred. Also, the second
amplitude is, for example, 1.5 times the amplitude of each phase current in a case in
which failure of the power conversion units 10 and 20 is not currently occurred. Also,
20 the failure determiner 33 may determine whether values of inter-terminal voltage of the
filter capacitors FC1 and FC2 are less than or equal to first voltage or are greater than or
equal to second voltage greater than the first voltage. The first voltage is, for example,
one-half of a value of inter-terminal voltage of each of the filter capacitors FC1 and FC2
in a case in which failure of the power conversion units 10 and 20 is not currently
25 occurred. Also, the second amplitude is, for example, 1.5 times a value of inter-terminal
voltage of each of the filter capacitors FC1 and FC2 in a case in which failure of the
power conversion units 10 and 20 is not currently occurred.
[0061] In the above-described embodiments, each of the contactor controller 31, the
switching controller 32 and the failure determiner 33 is provided independently of the
22
power conversion units 10 and 20. However, each of the power conversion units 10 and
20 may be provided with the contactor controller 31, the switching controller 32 and the
failure determiner 33. In this case, the contactor controller 31 provided for the power
conversion unit 10 controls the first contactor MC11. Also, the switching controller 32
provided for the power conversion unit 10 controls the switching elements 5 provided for
the power converter 11. Also, the failure determiner 33 provided for the power
conversion unit 10 determines the presence or absence of the failure of the power
conversion unit 10. Similarly, the contactor controller 31 provided for the power
conversion unit 20 controls the first contactor MC21. Also, the switching controller 32
10 provided for the power conversion unit 20 controls the switching elements provided for
the power converter 21. Also, the failure determiner 33 provided for the power
conversion unit 20 determines the presence or absence of the failure of the power
conversion unit 20.
[0062] The load 7 is a freely-selected electric device or electronic device mounted
15 on a railway vehicle. As an example, the load 7 is a lighting device, an air conditioner
or the like.
[0063] 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
20 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.
25 Reference Signs List
[0064] 1, 2 Power conversion device
3 Overhead line
4 Current collector
5 Transformer
23
6 Alternating-current filter capacitor
7 Load
10, 20 Power conversion unit
11, 21 Power converter
5 12 Switch
31 Contactor controller
32 Switching controller
33 Failure determiner
40 Iron core
10 41, 42 Coil
41a, 42a One end
41b, 42b Other end
F1, F2 Fuse
FC1, FC2 Filter capacitor
15 FL1, FL2 Filter reactor
MC11, MC21 First contactor
MC12, MC22 Second contactor
R1, R2 Resistor
S1 Contactor state signal
20 S2 Failure determination signal
24
We Claim:
1. A power conversion device comprising:
power conversion units connected in common to a power source, each power
conversion 5 unit including
a fuse to cut off an electrical path when direct current supplied from the
power source becomes greater than or equal to a threshold,
a power converter having primary terminals and secondary terminals and
configured to convert, into power supplied to a load connected to the secondary terminals,
10 direct-current power supplied from the power source via the primary terminals and to
supply the converted power to the load from the secondary terminals, and
a first contactor to electrically connect or electrically disconnect the power
converter to or from the power source; and
a contactor controller to close or open the first contactor included in each of the
15 power conversion units, wherein
when the direct current becomes greater than or equal to the threshold, the fuse
melts to cut off the electrical path, thereby electrically disconnecting, from the power
source, the power converter included in the power conversion unit including the melted
fuse.
20
2. The power conversion device according to claim 1, further comprising:
a failure determiner to determine presence or absence of failure of the power
conversion unit including the first contactor that is closed, wherein
the contactor controller opens the first contactor that is included in the power
25 conversion unit determined to be failed by the failure determiner among the power
conversion units, and closes a first contactor that is not closed and is included in another
power conversion unit among the power conversion units.
3. The power conversion device according to claim 1 or 2, wherein
25
the power conversion units each further include a filter reactor including an iron
core and a coil wound around the iron core, the filter reactor being configured to reduce a
harmonic component,
the power conversion units are connected in common to the load, and
the coil of the filter reactor provided for each of the power conversion 5 units is
wound around the common iron core.