1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
POWER CONVERSION DEVICE AND DISCONNECTION DETECTION METHOD
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
Title of Invention
POWER CONVERSION DEVICE AND DISCONNECTION DETECTION METHOD
5 Technical Field
[0001] The present disclosure relates to a power conversion device and a
disconnection detection method.
Background Art
[0002] Some electric railway vehicles are each equipped with a power conversion
10 device that converts, into desired alternating-current (AC) power, power supplied from a
substation through an overhead line and supplies the converted power to an electric motor.
Patent Literature 1 discloses an example of this type of power conversion device. This
power conversion device includes (i) filter capacitors, (ii) power converters that each
include primary terminals connected to one of the filter capacitors and convert
15 direct-current (DC) voltage applied to the one of the filter capacitors into desired AC
voltage to supply the AC voltage to an electric motor connected to secondary terminals,
and (iii) a discharge circuit that is shared by the filter capacitors and discharges the filter
capacitors.
Citation List
20 Patent Literature
[0003] Patent Literature 1: Unexamined Japanese Patent Application Publication
No. 2001-145208
Summary of Invention
25 Technical Problem
[0004] The power conversion device disclosed in Patent Literature 1 further
includes diodes for reverse current prevention. The anode of each diode is connected to
3
the corresponding one of the filter capacitors, and the cathode of each diode is connected
in common to the discharge circuit. The filter capacitors included in the power
conversion device mounted on an electric railway vehicle are charged to a high voltage.
Accordingly, during performance of maintenance work on the power conversion device,
the maintenance work is performed after a discharge switch is operated 5 to operate the
discharge circuit to discharge the filter capacitors. When some part of the diodes
included in this power conversion device have an open circuit failure, filter capacitors
connected to the diodes having the open circuit failure are not discharged even when the
discharge circuit operates. Since this power conversion device does not have a function
10 for determining whether an open circuit failure of a diode occurs, a worker who performs
the maintenance work is not notified of the presence of an undischarged filter capacitor.
Accordingly, a problem arises in that the worker cannot safely perform the maintenance
work.
[0005] In consideration of the aforementioned circumstances, an objective of the
15 present disclosure is to determine presence or absence of disconnection in a circuit from
each of filter capacitors to a shared discharge circuit.
Solution to Problem
[0006] In order to attain the aforementioned objective, a power conversion device
according to the present disclosure includes power converters, filter capacitors, at least
20 one contactor, a shared discharge circuit that is shared by the filter capacitors, a
determiner, and a disconnection detector. Each of the power converters converts, into
direct-current (DC) power or alternating-current (AC) power, DC power supplied from a
power source via primary terminals, and supplies the converted power to a load
connected to secondary terminals. Each of the filter capacitors is connected between
25 primary terminals of the corresponding one of the power converters. The at least one
contactor electrically connects or disconnects at least one of the power converters to or
from the power source. The shared discharge circuit is connected to the filter capacitors
4
and discharges the filter capacitors. The determiner determines whether the power
converters are electrically disconnected from the power source. When the determiner
determines that the power converters are electrically disconnected from the power source,
the disconnection detector determines, based on voltages of the filter capacitors, presence
or absence of disconnection in a circuit from each of the filter capacitors 5 to the shared
discharge circuit.
Advantageous Effects of Invention
[0007] According to the present disclosure, the presence or absence of
disconnection in a circuit from each of the filter capacitors to the shared discharge circuit
10 can be determined based on the voltages of the filter capacitors.
Brief Description of Drawings
[0008] FIG. 1 is a block diagram of a power conversion device according to
Embodiment 1 of the present disclosure;
FIG. 2 is a drawing illustrating an example of mounting, on an electric railway
15 vehicle, the power conversion device according to Embodiment 1;
FIG. 3 is a flowchart of operation for determining the presence or absence of
disconnection, the operation being performed by the power conversion device according
to Embodiment 1;
FIG. 4 is a block diagram of a power conversion device according to Embodiment
20 2 of the present disclosure;
FIG. 5 is a flowchart of operation for determining the presence or absence of
disconnection, the operation being performed by the power conversion device according
to Embodiment 2;
FIG. 6 is a flowchart of operation for determining the presence or absence of
25 disconnection, the operation being performed by a power conversion device according to
an embodiment of the present disclosure; and
FIG. 7 is a drawing illustrating an example of a manner of mounting, on an electric
5
railway vehicle, the power conversion device according to the embodiment of the present
disclosure.
Description of Embodiments
[0009] Power conversion devices according to embodiments of the present
disclosure are described below in detail with reference to drawings. 5 In the drawings,
components that are the same or equivalent are assigned the same reference sign.
[0010] Embodiment 1
An electric railway vehicle is equipped with a power conversion device that (i)
converts, into AC power, DC power supplied from a substation through an overhead line
10 and (ii) supplies the AC power to an electric motor. A power conversion device 1
according to Embodiment 1 illustrated in FIG. 1 converts the supplied DC power into AC
power for driving electric motors 51 and 52, and supplies the AC power to the electric
motors 51 and 52. FIG. 2 illustrates an example of mounting the power conversion
device 1 on the electric railway vehicle. FIG. 2 illustrates an example of a DC-feeding
15 system. A current collector 4 acquires DC power from the substation via an overhead
line 3 and supplies the acquired power to the power conversion device 1 via a high-speed
circuit breaker 5. The current collector 4 corresponds to a power source that supplies
power to the power conversion device 1. The high-speed circuit breaker 5 is controlled
by a non-illustrated circuit breaker controller and electrically connects the current
20 collector 4 and the power conversion device 1 or electrically disconnects the power
conversion device 1 from the current collector 4. The electric motors 51 and 52 are
configured as, for example, three-phase induction motors. When the power conversion
device 1 supplies power to the electric motors 51 and 52, the electric motors 51 and 52
are driven, and propulsion of the electric railway vehicle is obtained.
25 [0011] As illustrated in FIG. 2, the power conversion device 1 includes a positive
electrode input terminal 1a connected to the high-speed circuit breaker 5 and a negative
electrode input terminal 1b that is grounded. Also, the power conversion device 1
6
includes (i) contactors MC1 and MC2 each having one end connected to the positive
electrode input terminal 1a; (ii) a filter reactor FL1 having one end connected to another
end of the contactor MC1; (iii) a filter reactor FL2 having one end connected to another
end of the contactor MC2; (iv) a filter capacitor FC1 having: one end connected to
another end of the filter reactor FL1; and another end connected to the 5 negative electrode
input terminal 1b; and (v) a filter capacitor FC2 having: one end connected to another end
of the filter reactor FL2, and another end connected to the negative input terminal 1b.
[0012] The power conversion device 1 further includes (i) a power converter 11
having: primary terminals between which the filter capacitor FC1 is connected, and
10 secondary terminals each connected to the electric motor 51; (ii) a power converter 12
having primary terminals between which the filter capacitor FC2 is connected, and
secondary terminals each connected to the electric motor 52; and (iii) a shared discharge
circuit 15 that discharges the filter capacitors FC1 and FC2. The power conversion
device 1 further includes (i) a diode D1 having an anode connected to a connection point
15 between the other end of the contactor MC1 and the one end of the filter reactor FL1, and
a cathode connected to the shared discharge circuit 15; (ii) a diode D2 having an anode
connected to a connection point between the other end of the contactor MC2 and the one
end of the filter reactor FL2, and a cathode connected to the shared discharge circuit 15,
and (iii) a voltage measurer 13 connected in parallel to the filter capacitor FC1; and (iv) a
20 voltage measurer 14 connected in parallel to the filter capacitor FC2.
[0013] The power conversion device 1 further includes (i) a switching controller 16
that controls the power converters 11 and 12, (ii) a determiner 17 that determines whether
the power converters 11 and 12 are electrically disconnected from the current collector 4,
and (iii) a disconnection detector 18 that determines whether a disconnection occurs in a
25 circuit from the filter capacitors FC1 and FC2 to the shared discharge circuit 15.
[0014] The contactors MC1 and MC2 are closed or opened by a non-illustrated
contactor controller. When the contactor MC1 is closed, the high-speed circuit breaker
7
5 and the filter reactor FL1 are electrically connected. When the high-speed circuit
breaker 5 and the contactor MC1 are closed, the power converter 11 is electrically
connected to the current collector 4. When the contactor MC2 is closed, the high-speed
circuit breaker 5 and the filter reactor FL2 are electrically connected. When the
high-speed circuit breaker 5 and the contactor MC2 are closed, the power 5 converter 12 is
electrically connected to the current collector 4. With the high-speed circuit breaker 5
and the contactors MC1 and MC2 closed, the filter reactors FL1 and FL2 reduce
harmonic components. Also, DC voltage is applied to the filter capacitors FC1 and FC2.
Also, when the contactor MC1 is opened, the high-speed circuit breaker 5 and the filter
10 reactor FL1 are electrically disconnected from each other. As a result, the power
converter 11 is electrically disconnected from the current collector 4. When the
contactor MC2 is opened, the high-speed circuit breaker 5 and the filter reactor FL2 are
electrically disconnected from each other. As a result, the power converter 12 is
electrically disconnected from the current collector 4.
15 [0015] The power converter 11 converts the DC power supplied via the primary
terminals into three-phase AC power, and supplies the three-phase AC power to the
electric motor 51 to which each secondary terminal is connected. The power converter
12 converts the DC power supplied via the primary terminals into three-phase AC power,
and supplies the three-phase AC power to the electric motor 52 to which each secondary
20 terminal is connected. The power converters 11 and 12 are configured as, for example,
a variable voltage variable frequency (VVVF) inverter.
[0016] The shared discharge circuit 15 is a discharge circuit shared by the filter
capacitors FC1 and FC2, and includes a resistor R1 and a switch SW1 that are connected
in series. The switch SW1 is configured as, for example, a knife switch for discharging.
25 An operator mechanically operates the switch SW1 that is a knife switch for discharging,
thereby turning on or off the switch SW1. When the switch SW1 is turned on in a state
in which the power converters 11 and 12 are electrically disconnected from the current
8
collector 4, the shared discharge circuit 15 discharges the filter capacitors FC1 and FC2.
[0017] The diode D1 prevents current from flowing back from the shared discharge
circuit 15 to the filter capacitor FC1 when the switch SW1 is turned on. The diode D2
prevents current from flowing back from the shared discharge circuit 15 to the filter
capacitor FC2 when the switch 5 SW1 is turned on.
The voltage measurer 13 measures a value of an inter-terminal voltage of the filter
capacitor FC1, and supplies a signal indicating the measured voltage value to the
switching controller 16 and the determiner 17. The voltage measurer 14 measures a
value of inter-terminal voltage of the filter capacitor FC2, and supplies a signal indicating
10 the measured voltage value to the switching controller 16 and the determiner 17.
[0018] An operation command is supplied from a non-illustrated cab to the
switching controller 16. The operation command includes a powering command
indicating target acceleration of the electric railway vehicle, a brake command indicating
target deceleration of the electric railway vehicle, or the like. As described later, in
15 accordance with the operation command, the switching controller 16 sends switching
control signals S1 to the switching elements included in the power converters 11 and 12
to control the switching elements.
[0019] The determiner 17 determines whether the power converters 11 and 12 are
electrically disconnected from the current collector 4. Specifically, the determiner 17
20 acquires contactor control signals supplied to the contactors MC1 and MC2 by the
contactor controller, and determines, based on the contactor control signals, whether the
contactors MC1 and MC2 are opened. The determiner 17 notifies the disconnection
detector 18 as to whether the contactors MC1 and MC2 are opened. For example, the
determiner 17 outputs, to the disconnection detector 18, a determination signal S2 that
25 becomes a high level when the contactors MC1 and MC2 are opened and that becomes a
low level when at least one of the contactors MC1 and MC2 is closed.
[0020] The disconnection detector 18 acquires, from the voltage measurer 13, a
9
voltage EFC1 that is the value of inter-terminal voltage of the filter capacitor FC1,
acquires, from the voltage measurer 14, a voltage EFC2 that is the value of inter-terminal
voltage of the filter capacitor FC2, and determines, based on the voltages EFC1 and
EFC2, the presence or absence of disconnection in the circuit from one end of each of the
filter capacitors FC1 and FC2 to the shared discharge circuit 15. An open 5 circuit failure
of the diodes D1 and D2 is an example of this disconnection. For example, when the
open circuit failure of the diode D1 occurs, even when the switch SW1 of the shared
discharge circuit 15 is turned on, the filter capacitor FC1 is not discharged and only the
filter capacitor FC2 is discharged. As a result, although the voltage EFC1 can be
10 regarded as constant, the voltage EFC2 decreases. In other words, when only one of the
voltages EFC1 and EFC2 decreases during discharging of the filter capacitors FC1 and
FC2 by the shared discharge circuit 15, failure can be regarded to occur in the circuit
from either one of the filter capacitors FC1 and FC2 to the shared discharge circuit 15.
[0021] Accordingly, the disconnection detector 18 determines the presence or
15 absence of circuit disconnection based on the voltages EFC1 and EFC2 during
discharging of the filter capacitors FC1 and FC2 by the shared discharge circuit 15.
Specifically, when the high-level determination signal S2 is supplied from the determiner
17, the disconnection detector 18 determines whether one of the voltages EFC1 and
EFC2 is higher than a first reference voltage Th1 and the other one of the voltages EFC1
20 and EFC2 is lower than or equal to a second reference voltage Th2 lower than the first
reference voltage Th1, and outputs a determination result.
[0022] Specifically, when the voltage EFC1 is higher than the first reference
voltage Th1 and the voltage EFC2 is lower than or equal to the second reference voltage
Th2, the disconnection detector 18 outputs, as a determination result to a display device
25 provided in the cab, a disconnection detection signal S3 having an amplitude
corresponding to the filter capacitor FC1. Also, when the voltage EFC1 is lower than or
equal to the second reference voltage Th2 and the voltage EFC2 is higher than the first
10
reference voltage Th1, the disconnection detector 18 outputs, as a determination result to
the display device, a disconnection detection signal S3 having an amplitude
corresponding to the filter capacitor FC2. Also, when the disconnection detector 18
determines that the voltage EFC1 and the voltage EFC2 are higher than the first reference
voltage Th1 or the voltage EFC1 and the voltage EFC2 are lower than 5 or equal to the
second reference voltage Th2, the disconnection detector 18 outputs, as a determination
result to the display device, a disconnection detection signal S3 having an amplitude
lower than the amplitudes corresponding to the filter capacitors FC1 and FC2.
[0023] The display device can determine, based on the amplitudes of the
10 disconnection detection signals S3, which of the following states (i) to (iii) occurs: (i) no
disconnection occurs in the circuit from each of the filter capacitors FC1 and FC2 to the
shared discharge circuit 15; (ii) disconnection occurs in the circuit from the filter
capacitor FC1 to the shared discharge circuit 15; and (iii) disconnection occurs in the
circuit from the filter capacitor FC2 to the shared discharge circuit 15.
15 [0024] The determiner 17 beforehand holds the first reference voltage Th1 and the
second reference voltage Th2. The first reference voltage Th1 and the second reference
voltage Th2 are determined in accordance with the values of inter-terminal voltages of
the filter capacitors FC1 and FC2 in a state in which the filter capacitors FC1 and FC2 are
charged. For example, the first reference voltage Th1 is 2/3 of the inter-terminal voltage
20 values of the fully-charged filter capacitors FC1 and FC2, and the second reference
voltage Th2 is 1/3 of the inter-terminal voltage values of the fully-charged filter
capacitors FC1 and FC2.
[0025] Next, operation of the power conversion device 1 having the above
configuration is described.
25 When operation of a raising switch for raising a pantograph that is an example of
the current collector 4 is performed at the start of operation of the electric railway vehicle
and the current collector 4 comes into contact with the overhead line 3, the current
11
collector 4 is supplied with power from the substation. After the high-speed circuit
breaker 5 is closed, the contactors MC1 and MC2 are closed. As a result, power is
supplied to the power conversion device 1.
[0026] During operation of the electric railway vehicle, an operation command
from the non-illustrated cab is input to the switching controller 16. When 5 the operation
command includes a powering command, that is, when powering operation of the electric
railway vehicle is performed, the switching controller 16 controls the switching elements
of the power converters 11 and 12 so as to cause the power converters 11 and 12 to
convert DC power into three-phase AC power for driving the electric motors 51 and 52.
10 The switching controller 16 calculates a target torque for acquiring a target acceleration
indicated by the powering command. Also, the switching controller 16 measures values
of currents flowing in the electric motors 51 and 52 by using a non-illustrated current
measurer, and calculates actual torque of the electric motors 51 and 52 from the measured
current values. Specifically, the switching controller 16 acquires, from the current
15 measurer that measures values of the U-phase, V-phase, and W-phase currents flowing in
the electric motors 51 and 52, the values of the phase currents flowing in the electric
motors 51 and 52, and calculates the actual torque of the electric motors 51 and 52 from
the values of the phase currents. The switching controller 16 transmits the switching
control signals S1 to the switching elements of the power converters 11 and 12 to control
20 the switching elements so that the actual torque of the electric motors 51 and 52 is made
to approach the target torque. By charging the filter capacitors FC1 and FC2 connected
between the primary terminals of the power converters 11 and 12, noise generated by the
power converters 11 and 12 is reduced.
[0027] In a case in which maintenance work of the power conversion device 1 is
25 performed, the high-speed circuit breaker 5 and the contactors MC1 and MC2 are opened
after the power converters 11 and 12 are stopped. As a result, the power converters 11
and 12 are electrically disconnected from the current collector 4. Before performing the
12
maintenance work, a maintenance worker mechanically operates the switch SW1 that is a
knife switch for discharging, thereby turning on the switch SW1. When the switch
SW1 is turned on with the contactors MC1 and MC2 opened, the filter capacitors FC1
and FC2 are discharged.
[0028] When disconnection occurs in the circuit from each of the 5 filter capacitors
FC1 and FC2 to the shared discharge circuit 15, the filter capacitors FC1 and FC2 are not
discharged even when the switch SW1 is turned on, so that the maintenance work cannot
be performed safely. Accordingly, when the power conversion device 1 is supplied
with a contactor control signal indicating that the contactors MC1 and MC2 are opened,
10 the power conversion device 1 starts processing to determine the presence or absence of
the disconnection in the circuit from each of the filter capacitors FC1 and FC2 to the
shared discharge circuit 15. The processing of determining the presence or absence of
disconnection that is performed by the power conversion device 1 is described with
reference to FIG. 3.
15 [0029] The determiner 17 determines whether the contactors MC1 and MC2 are
opened (step S11). The determiner 17 outputs, to the disconnection detector 18, the
determination signal S2 indicating a determination result. When the determiner 17
determines that at least one of the contactors MC1 and MC2 is not opened (No in step
S11), the process of step S11 is repeated. At this time, since the determiner 17 supplies
20 the low-level determination signal S2 to the disconnection detector 18, the disconnection
detector 18 does not perform the processes of step S12 and the subsequent steps
described later.
[0030] When the determiner 17 determines that the contactors MC1 and MC2 are
opened (Yes in step S11), the determiner 17 outputs the high-level determination signal
25 S2 to the disconnection detector 18, and the disconnection detector 18 performs the
processes of step S12 and the subsequent steps described later. Since the determiner 17
performs the process of step S11, the processes of step S12 and the subsequent steps are
13
not performed even when, in a state in which the high-speed circuit breaker 5 and the
contactors MC1 and MC2 are closed, for example, fluctuations of the voltages EFC1 and
EFC2 occur due to fluctuation of the DC voltage of the overhead line 3, or fluctuations of
the voltages EFC1 and EFC2 occur during a regenerative operation or the like.
Accordingly, determination that the circuit is disconnected is prevented 5 from being
erroneously made due to fluctuations of the voltages EFC1 and EFC2.
[0031] When the high-level determination signal S2 is supplied, the disconnection
detector 18 respectively acquires the voltages EFC1 and EFC2 from the voltage
measurers 13 and 14 (step S12). The disconnection detector 18 compares the voltages
10 EFC1 and EFC2 with the first reference voltage Th1 (step S13).
[0032] When the disconnection detector 18 determines that the voltage EFC1 is
higher than the first reference voltage Th1 and the voltage EFC2 is higher than the first
reference voltage Th1 (Yes in step S13), the disconnection detector 18 determines
whether a given determination time is elapsed after the contactors MC1 and MC2 are
15 opened (step S14). Specifically, when the disconnection detector 18 is supplied with the
high-level determination signal S2, the disconnection detector 18 starts a timer and
determines whether measurement time of the timer reaches the determination time. The
determination time is the time required for the voltages EFC1 and EFC2 to drop to the
first reference voltage Th1 after the filter capacitors FC1 and FC2 started discharging
20 from the fully charged state of the filter capacitors FC1 and FC2 in a state in which no
disconnection occurs in the circuit from each of the filter capacitors FC1 and FC2 to the
shared discharge circuit 15.
[0033] When the disconnection detector 18 determines that the determination time
is elapsed (Yes in step S14), the disconnection detector 18 outputs, to the display device,
25 information to the effect that the filter capacitors FC1 and FC2 are not normally
discharged (step S15), and the disconnection detector 18 ends the processing of
determining the presence or absence of disconnection. When the disconnection detector
14
18 determines that the determination time is not elapsed (No in step S14), the
above-described processing is repeated from step S11.
[0034] When the disconnection detector 18 determines that at least one of the
voltages EFC1 and EFC2 is lower than or equal to the first reference voltage Th1 (No in
step S13), the disconnection detector 18 determines whether one of 5 the voltages EFC1
and EFC2 is higher than the first reference voltage Th1 and the other one of the voltages
EFC1 and EFC2 is lower than or equal to the second reference voltage Th2 (step S16).
[0035] When the disconnection detector 18 determines that the voltage EFC1 is
higher than the first reference voltage Th1 and the voltage EFC2 is lower than or equal to
10 the second reference voltage Th2 (Yes in step S16), the disconnection detector 18 outputs,
to the display device, the disconnection detection signal S3 having the amplitude
corresponding to the filter capacitor FC1 (step S17).
Also, when the disconnection detector 18 determines that the voltage EFC1 is
lower than or equal to the second reference voltage Th2 and the voltage EFC2 is higher
15 than the first reference voltage Th1 (Yes in step S16), the disconnection detector 18
outputs, to the display device, the disconnection detection signal S3 having the amplitude
corresponding to the filter capacitor FC2 (step S17). When the process of step S17 is
completed, the power conversion device 1 ends the processing of determining the
presence or absence of disconnection.
20 [0036] As described above, according to the power conversion device 1 according
to Embodiment 1, the presence or absence of disconnection in the circuit from each of the
filter capacitors FC1 and FC2 to the shared discharge circuit 15 can be determined based
on the voltages EFC1 and EFC2.
[0037] Embodiment 2
25 When disconnection occurs in the circuit from each of the filter capacitors FC1 and
FC2 to the shared discharge circuit 15, the filter capacitors FC1 and FC2 cannot be
discharged by the shared discharge circuit 15. Accordingly, in a case in which
15
disconnection occurs in the circuit from the filter capacitors FC1 and FC2 to the shared
discharge circuit 15, a power conversion device 2 according to Embodiment 2 operates
individual discharge circuits provided for preventing the voltages EFC1 and EFC2 from
becoming overvoltages, thereby discharging each of the filter capacitors FC1 and FC2.
[0038] The timing of operation of these individual discharge circuits 5 is described.
For example, in order to prevent the voltages EFC1 and EFC2 from becoming
overvoltages when outputs of the power converters 11 and 12 become abnormal and the
power converters 11 and 12 are stopped, the power conversion device 2 includes two
individual discharge circuits that are each connected to the corresponding one of the filter
10 capacitors FC1 and FC2. The power conversion device 2 discharges the filter capacitors
FC1 and FC2 by operating the individual discharge circuits when the outputs of the
power converters 11 and 12 become abnormal.
Also, during regenerative braking of the electric railroad vehicle, that is, while the
regenerative braking force is being applied to the electric railroad vehicle by making the
15 electric motors 51 and 52 operate as generators to supply to the overhead line 3 power
generated by the electric motors 51 and 52, the electric power conversion device 2
operates these individual discharge circuits in order to prevent the voltages EFC1 and
EFC2 from becoming too high in comparison to the voltage of the overhead line 3.
Additionally, by operating these individual discharge circuits even when
20 disconnection occurs in the circuit from the filter capacitors FC1 and FC2 to the shared
discharge circuit 15, maintenance work can be performed safely.
[0039] In addition to the configuration of the power conversion device 1 according
to Embodiment 1, the power conversion device 2 according to Embodiment 2 illustrated
in FIG. 4 further includes (i) an individual discharge circuit 19 connected in parallel to the
25 filter capacitor FC1, (ii) an individual discharge circuit 20 connected in parallel to the
filter capacitor FC2, and (iii) a discharge controller 21 that controls operation of the
individual discharge circuits 19 and 20.
16
[0040] Each component of the power conversion device 2 different from the power
conversion device 1 according to Embodiment 1 is described.
The individual discharge circuit 19 includes a resistor R2 and a switching element
SW2 that are connected in series. When the switching element SW2 is turned on by
control performed by the discharge controller 21, the individual discharge 5 circuit 19
discharges the filter capacitor FC1. The individual discharge circuit 20 includes a
resistor R3 and a switching element SW3 that are connected in series. When the
switching element SW3 is turned on by control performed by the discharge controller 21,
the individual discharge circuit 20 discharges the filter capacitor FC2. The switching
10 elements SW2 and SW3 are configured as, for example, insulated gate bipolar transistors
(IGBT).
[0041] When the outputs of the power converters 11 and 12 becomes abnormal and
the switching controller 16 stops the power converters 11 and 12, the discharge controller
21 turns on the switching elements SW2 and SW3. Specifically, when the power
15 converters 11 and 12 are stopped due to the abnormality in the output of the power
converters 11 and 12, the switching controller 16 supplies, to the discharge controller 21,
protection stop signals S4 that are stop signals for protection and indicate the stopped
power converters 11 and 12. When the protection stop signal S4 indicating the power
converter 11 is supplied to the discharge controller 21, the discharge controller 21 turns
20 on the switching element SW2 provided for the individual discharge circuit 19 connected
to the power converter 11. Also, when the protection stop signal S4 indicating the
power converter 12 is supplied to the discharge controller 21, the discharge controller 21
turns on the switching element SW3 provided for the individual discharge circuit 20
connected to the power converter 12.
25 [0042] Also, when the voltages of the filter capacitors FC1 and FC2 are higher than
or equal to a threshold voltage during the regenerative operation of the electric railway
vehicle, the discharge controller 21 turns on the switching elements SW2 and SW3.
17
Specifically, the discharge controller 21 acquires an operation command from the cab,
acquires the voltage EFC1 from the voltage measurer 13, and acquires the voltage EFC2
from the voltage measurer 14. When the operation command includes a brake
command and the voltage EFC1 is higher than or equal to the threshold voltage, the
discharge controller 21 turns on the switching element SW2. Also, 5 when the operation
command includes the brake command and the voltage EFC2 is higher than or equal to
the threshold voltage, the discharge controller 21 turns on the switching element SW3.
The threshold voltage is determined in accordance with the DC voltage of the overhead
line 3 and is a voltage in a range in which regenerative operation is possible and
10 overvoltage does not occur in the overhead line 3.
[0043] Additionally, when the disconnection detection signal S3 indicating the filter
capacitor FC1 is supplied to the discharge controller 21, the discharge controller 21 turns
on the switching element SW2. As a result, the filter capacitor FC1 is discharged.
Also, when the disconnection detection signal S3 indicating the filter capacitor FC2 is
15 supplied to the discharge controller 21, the discharge controller 21 turns on the switching
element SW3. As a result, the filter capacitor FC2 is discharged.
[0044] Next, operation of the power conversion device 2 having the
above-described configuration is described. The operations of power conversion device
2 at the time of starting the operation of the electric railway vehicle and at the time of
20 braking of the electric railway vehicle are the same as in Embodiment 1.
Like the power conversion device 1 according to Embodiment 1, when a contactor
control signal indicating that the contactors MC1 and MC2 are opened is supplied, the
power conversion device 2 starts the processing of determining the presence or absence
of disconnection in the circuit from each of the filter capacitors FC1 and FC2 to the
25 shared discharge circuit 15. The processing for determining the presence or absence of
the disconnection, which is performed by the power conversion device 2, is described
with reference to FIG. 5.
18
[0045] The processes of steps S11-S17 are the same as those of steps S11-S17 of
FIG 3. When the process of step S17 is completed, the discharge controller 21 switches
on and off the switching elements SW2 and SW3 in accordance with the disconnection
detection signals S3 output by the disconnection detector 18, and the individual discharge
circuits 19 and 20 discharge the filter capacitors FC1 and FC2 (step S18). 5 Specifically,
when the disconnection detection signal S3 having the amplitude corresponding to the
filter capacitor FC1 is supplied to the discharge controller 21, the discharge controller 21
turns on the switching element SW2 to operate the individual discharge circuit 19,
thereby discharging the filter capacitor FC1. Also, when the disconnection detection
10 signal S3 having the amplitude corresponding to the filter capacitor FC2 is supplied to the
discharge controller 21, the discharge controller 21 turns on the switching element SW3
to operate the individual discharge circuit 20 to discharge the filter capacitor FC2.
[0046] As described above, according to the power conversion device 2 according
to Embodiment 2, when the shared discharge circuit 15 cannot discharge the filter
15 capacitors FC1 and FC2 due to the disconnection, the filter capacitors FC1 and FC2 can
be discharged by the individual discharge circuits 19 and 20. This enables the providing
of the power conversion device 2 that is highly safe.
[0047] Embodiments of the present disclosure are not limited to the
above-described embodiments. For example, the determiner 17 can determine whether
20 each of the contactors MC1 and MC2 is opened based on a contact signal output from
each of the contactors MC1 and MC2. The contact signal is assumed to indicate
whether electricity is conducted at a point of contact of each of the contactors MC1 and
MC2.
Also, the determiner 17 may determine whether the high-speed circuit breaker 5 is
25 opened. Specifically, the determiner 17 can determine, based on a control signal
transmitted to the high-speed circuit breaker 5 by the circuit breaker controller or a
contact signal output by the high-speed circuit breaker 5, whether the high-speed circuit
19
breaker 5 is opened. The contact signal is assumed to indicate whether electricity is
conducted at a point of contact of the high-speed circuit breaker 5.
[0048] Also, in addition to the above-described determination processing, the
determiner 17 may further perform determination processing for preventing erroneous
detection in the disconnection detector 18. One example of 5 the determination
processing performed by the determiner 17 is described with reference to FIG. 6. The
processes of steps S11-S17 of FIG. 6 are the same as those of steps S11-S17 of FIG. 3.
When the determiner 17 determines that the contactors MC1 and MC2 are opened (Yes
in step S11), the determiner 17 determines whether all the switching elements provided
10 for each of the power converters 11 and 12 are turned off (step S19).
[0049] The determination as to whether all the switching elements provided for
each of the power converters 11 and 12 are turned off is made based on the switching
control signals S1 that the switching controller 16 supplies to the power converters 11 and
12. Specifically, the determiner 17 acquires the switching control signals S1 and
15 determines, based on the switching control signals S1, whether all the switching elements
provided for the power converters 11 and 12 are turned off.
[0050] When the determiner 17 determines that at least one switching element
provided for the power converters 11 and 12 is turned on (No in step S19), the process of
step S11 is repeated. In this case, since the determiner 17 supplies the low-level
20 determination signal S2 to the disconnection detector 18, the disconnection detector 18
does not perform the processes of step S12 and the subsequent steps.
[0051] When the determiner 17 determines that all the switching elements provided
for each of the power converters 11 and 12 are turned off (Yes in step S19), the
determiner 17 outputs the high-level determination signal S2 to the disconnection
25 detector 18, and the disconnection detector 18 performs the processes of step S12 and the
subsequent steps.
[0052] Also, for example, the determiner 17 may determine whether the power
20
converters 11 and 12 are electrically disconnected from the current collector 4 and the
electric railway vehicle equipped with the power conversion devices 1 and 2 is stopped.
The determination as to whether the contactors MC1 and MC2 are opened is as described
in the above-described embodiments. The determination as to whether the electric
railway vehicle is stopped can be made based on speed of the electric 5 railway vehicle.
Specifically, the determiner 17 acquires speed of the electric railway vehicle from speed
sensors attached to the electric motors 51 and 52, and determines whether the electric
railway vehicle is stopped. The determiner 17 outputs the determination signal S2 that
(i) becomes a high level when the determiner 17 determines that the contactors MC1 and
10 MC2 are opened and the electric railway vehicle is stopped and (ii) becomes a low level
when the determiner 17 determines that at least one of the contactors MC1 and MC2 is
closed or the electric railway vehicle is not stopped.
[0053] The number of filter capacitors is a freely-selected value of 2 or more. For
example, a case in which the power conversion devices 1 and 2 each include three filter
15 capacitors FC1, FC2 and FC3 is described as an example. In this case, the power
conversion devices 1 and 2 are assumed to each include contactors MC1, MC2, and MC3
that electrically connect or disconnect corresponding power converters to or from the
current collector 4. Also, values of the inter-terminal voltages of the filter capacitors
FC1, FC2 and FC3 measured by the voltage measurer are assumed to be respectively
20 EFC1, EFC2 and EFC3. The determiner 17 determines whether the contactors MC1,
MC2 and MC3 are opened. The disconnection detector 18 determines whether at least
one of the voltages EFC1, EFC2 and EFC3 is higher than the first reference voltage Th1
and at least another one of the voltages EFC1, EFC2 and EFC3 is lower than or equal to
the second reference voltage Th2, and outputs determination results. For example,
25 when the voltage EFC1 is higher than the first reference voltage Th1 and the voltage
EFC3 is lower than or equal to the second reference voltage Th2, the disconnection
detector 18 outputs the disconnection detection signal S3 indicating the filter capacitor
21
FC3.
[0054] The disconnection detector 18 may determine whether a difference between
the voltages EFC1 and EFC2 is greater than or equal to a reference voltage difference and
may output a determination result. Specifically, when the disconnection detector 18
determines that a voltage difference between the voltages EFC1 and 5 EFC2 is or greater
than or equal to the reference voltage difference, the disconnection detector 18 outputs, as
a determination result to the display device, the disconnection detection signal S3 having
the amplitude corresponding to the filter capacitor FC1 or FC2 that has a higher
inter-terminal voltage among the filter capacitors FC1 and FC2. Specifically, when the
10 voltage difference between the voltages EFC1 and EFC2 is greater than or equal to the
reference voltage difference and the voltage EFC1 is higher than the voltage EFC2, the
disconnection detector 18 outputs the disconnection detection signal S3 having the
amplitude corresponding to the filter capacitor FC1. Also, when the voltage difference
between the voltages EFC1 and EFC2 is greater than or equal to the reference voltage
15 difference and the voltage EFC2 is higher than the voltage EFC1, the disconnection
detector 18 outputs the disconnection detection signal S3 having the amplitude
corresponding to the filter capacitor FC2. The reference voltage difference is a voltage
difference such that, in a state in which one of the filter capacitors FC1 and FC2 can be
considered to be charged, the other one of the filter capacitors FC1 and FC2 can be
20 considered to be discharged. For example, the reference voltage difference is 1/3 of the
inter-terminal voltage of the fully-charged filter capacitors FC1 and FC2.
[0055] The processing by the disconnection detector 18 is described by taking as an
example a case in which the power conversion devices 1 and 2 each include the three
filter capacitors FC1, FC2 and FC3. The disconnection detector 18 calculates the
25 voltage difference between the voltages EFC1 and EFC2, a voltage difference between
the voltages EFC1 and EFC3, and a voltage difference between the voltages EFC2 and
EFC3. Each of the calculated voltage differences is compared with the reference
22
voltage difference, determination as to whether at least one of the calculated voltage
differences is greater than or equal to the reference voltage difference is made, and a
determination result is output. For example, when the voltage difference between the
voltages EFC1 and EFC3 is greater than or equal to the reference voltage difference and
the voltage EFC3 is higher than the voltage EFC1, the disconnection detector 5 18 outputs
the disconnection detection signal S3 having the amplitude corresponding to the filter
capacitor FC3.
[0056] The power conversion devices 1 and 2 may determine whether at least one
of the voltages EFC1 and EFC2 is higher than the second threshold voltage Th2 after
10 elapse of the time required for discharging after the contactors MC1 and MC2 are closed,
and may output a determination result to the display device. As a result, when the filter
capacitors FC1 and FC2 are not discharged, an operation in which maintenance work is
not performed is possible.
[0057] The power conversion devices 1 and 2 can be mounted on a freely-selected
15 vehicle or a freely-selected device that can supply DC power to the power conversion
devices 1 and 2.
As an example, the power conversion devices 1 and 2 can be mounted on an electric
railway vehicle of an AC power feeding system. FIG. 7 illustrates a power conversion
device 10 mounted on an electric railway vehicle of the AC power feeding system. AC
20 power is supplied, via the high-speed circuit breaker 5, from the current collector 4 that
acquires the AC power from the substation via the overhead line 3 to primary terminals
of a transformer 6. The transformer 6 steps down the voltage of the AC power supplied
to the primary terminals, and supplies the stepped-down AC power from the secondary
terminals to the power conversion device 10.
25 [0058] The power conversion device 10 includes (i) a contactor MC4 as a substitute
for the contactors MC1 and MC2 that is connected to a secondary terminal of the
transformer 6, and (ii) a converter 22 that converts, into DC power, AC power supplied to
23
primary terminals and outputs the DC power from secondary terminals. The contactor
MC3 electrically connects or disconnects the power converters 11 and 12 to or from the
current collector 4. The determiner 17 provided for the power conversion device 10
illustrated in FIG. 7 determines whether the contactor MC4 is closed.
Also, the power conversion devices 1 and 2 can be mounted 5 not only on the
electric railway vehicle but also on a diesel railcar.
[0059] The shared discharge circuit 15 has a freely-selected configuration as long as
the shared discharge circuit 15 is a circuit that discharges the filter capacitors FC1 and
FC2. Elements provided in the circuit from the filter capacitors FC1 and FC2 to the
10 shared discharge circuit 15 are not limited to the diodes D1 and D2, and a circuit having a
freely-selected configuration can be provided as long as the circuit enables the shared
discharge circuit 15 to discharge the filter capacitors FC1 and FC2.
[0060] The power converters 11 and 12 are not limited to the VVVF inverter, and
can be freely selected as long as the power converters 11 and 12 are devices that convert
15 DC power supplied to the primary terminals into DC or AC power and supply the
converted power to a load connected to the secondary terminals. For example, the
power converters 11 and 12 are configured as a DC-DC converter or a static inverter that
supplies power to a lighting apparatus, an air conditioner or the like. Also, for example,
the power converter 11 is configured as a VVVF inverter, and the power converter 12 is
20 configured as a static inverter. Also, a load connected to the secondary terminals of the
power converter 11 may be different in type from a load connected to the secondary
terminals of the power converter 12.
[0061] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
25 persons skilled in the art will recognize that changes may be made in form and detail
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
24
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.
Reference Signs List
[0062] 1, 2, 10 Power 5 conversion device
1a Positive electrode input terminal
1b Negative electrode input terminal
3 Overhead line
4 Current collector
10 5 High-speed circuit breaker
6 Transformer
11, 12 Power converter
13, 14 Voltage measurer
15 Shared discharge circuit
15 16 Switching controller
17 Determiner
18 Disconnection detector
19, 20 Individual discharge circuit
21 Discharge controller
20 22 Converter
51, 52 Electric motor
D1, D2 Diode
FC1, FC2, FC3 Filter capacitor
FL1, FL2 Filter reactor
25 MC1, MC2, MC3, MC4 Contactor
R1, R2, R3 Resistor
S1 Switching control signal
25
S2 Determination signal
S3 Disconnection detection signal
S4 Protection stop signal
SW1 Switch
SW2, SW3 5 Switching element
26
We Claim :
1. A power conversion device comprising:
power converters each to convert, into direct-current power or alternating-current
power, direct-current power supplied from a power source via primary terminals and
supply the converted power to a load connected to secondary 5 terminals;
filter capacitors each connected between the primary terminals of the
corresponding one of the power converters;
at least one contactor to electrically connect or disconnect at least one of the power
converters to or from the power source;
10 a shared discharge circuit that is shared by the filter capacitors and is connected to
the filter capacitors, the shared discharge circuit being configured to discharge the filter
capacitors;
a determiner to determine whether the power converters are electrically
disconnected from the power source; and
15 a disconnection detector to determine, based on voltages of the filter capacitors,
presence or absence of disconnection in a circuit from each of the filter capacitors to the
shared discharge circuit when the determiner determines that the power converters are
electrically disconnected from the power source.
20 2. The power conversion device according to claim 1, wherein
the disconnection detector
determines whether an inter-terminal voltage of at least one of the filter
capacitors is higher than a first reference voltage and an inter-terminal voltage of at least
another one of the filter capacitors is lower than or equal to a second reference voltage
25 that is lower than the first reference voltage, and
outputs a determination result.
27
3. The power conversion device according to claim 2, wherein
when the inter-terminal voltage of the at least one of the filter capacitors is higher
than the first reference voltage and the inter-terminal voltage of the at least another one of
the filter capacitors is lower than or equal to the second reference voltage, the
disconnection detector outputs, as the determination result, a disconnection 5 detection
signal indicating the at least one of the filter capacitors.
4. The power conversion device according to claim 1, wherein
the disconnection detector
10 determines whether a difference between an inter-terminal voltage of one
filter capacitor among the filter capacitors and an inter-terminal voltage of another filter
capacitor among the filter capacitors is higher than or equal to a reference voltage, and
outputs a determination result.
15 5. The power conversion device according to claim 4, wherein
when the difference between the inter-terminal voltage of the one filter capacitor
and the inter-terminal voltage of the another filter capacitor is higher than or equal to the
reference voltage, the disconnection detector outputs, as the determination result, a
disconnection detection signal indicating a filter capacitor that has a higher inter-terminal
20 voltage among the one filter capacitor and the another filter capacitor.
6. The power conversion device according to any one of claims 1 to 5, further
comprising:
individual discharge circuits each connected to the corresponding one of the filter
25 capacitors, the individual discharge circuits being configured to each discharge the
connected one of the filter capacitors; and
a discharge controller to, when the disconnection detector detects presence of the
28
disconnection, operate an individual discharge circuit of the individual discharge circuits
that is connected to a filter capacitor of the filter capacitors that is connected to a circuit in
which the presence of the disconnection is detected.
7. The power conversion device according to any one of claims 5 1 to 6, wherein
the determiner determines whether the power converters are electrically
disconnected from the power source and are stopped, and
when the determiner determines that the power converters are electrically
disconnected from the power source and are stopped, the disconnection detector
10 determines, based on the voltages of the filter capacitors, the presence or absence of
disconnection in the circuit from each of the filter capacitors to the shared discharge
circuit.
8. The power conversion device according to any one of claims 1 to 7, wherein
15 the at least one contactor is a plurality of contactors, and
each of the contactors electrically connects or disconnects the corresponding power
converter of the power converters to or from the power source.
9. A disconnection detection method comprising:
20 determining whether power converters are electrically disconnected from the
power source, each of the power converters being configured to convert, into
direct-current power or alternating-current power, direct-current power supplied from a
power source via primary terminals and supply the converted power to a load connected
to secondary terminals; and
25 determining, based on voltages of filter capacitors each connected to the primary
terminals of the corresponding one of the power converters, presence or absence of
disconnection in a circuit from each of the filter capacitors to a shared discharge circuit
that is shared by the filter capacitors, upon determination that the power converters are
electrically disconnected from the power source.