FORM 2 THE PATENTS ACT, 1970 (39 of& 1970) THE PATENTS RULES, 2003
[SCeOeM PsLeEcTtEi oSnP E1C0I,F IRCuAlTeI O1N3 ]
POWER CONVERSION DEVICE AND ABNORMALITY 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 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
Field
[0001] The present invention relates to a power
conversion device that converts an 5 input power into a
desired power and outputs the power, and to an abnormality
detection method.
Background
10 [0002] Conventionally, there is known a power conversion
device that converts an input power into a desired power
and outputs the converted power to a load. For example, a
power conversion device described in Patent Literature 1 is
mounted on a railway vehicle, converts a direct-current
15 power input from an overhead wire into an alternatingcurrent
power after boosting the direct-current power to a
desired voltage, insulates the alternating-current power by
using a transformer, converts the alternating-current power
into a direct-current power, and then outputs the direct20
current power to a load. The power conversion device
described in Patent Literature 1 detects an overcurrent
caused by a load short-circuit or the like, by a measuring
instrument that measures a current value of a directcurrent
power output to a load; however, the power
25 conversion device cannot detect the overcurrent when the
measuring instrument malfunctions. Therefore, when
detecting a malfunction of the measuring instrument, the
power conversion device described in Patent Literature 1
stops its power conversion operation to protect internal
30 circuits of the power conversion device from an overcurrent
that cannot be detected when it is generated.
Citation List
3
Patent Literature
[0003] Japanese Patent Application Laid-open No. 2015-
139264
5 Summary
Technical Problem
[0004] However, in the conventional technique described
above, the power conversion device cannot detect an
abnormality of the measuring instrument that measures a
10 current value of a power input to the power conversion
device. The power conversion device has a problem of, in a
case where the measuring instrument that measures an input
current value is in an abnormal state, not being able to
detect an overcurrent of the input power and to protect the
15 internal circuits of the power conversion device.
[0005] The present invention has been achieved in view
of the above problems, and an object of the present
invention is to provide a power conversion device that can
detect an abnormality of a measuring instrument that
20 measures an input current value.
Solution to Problem
[0006] In order to solve the above-described problem and
achieve the object, a power conversion device of the
25 present invention includes a power converter to convert a
first power into a second power, a first current
measurement unit to measure a first current value that is a
current value of the first power, a second current
measurement unit to measure a second current value that is
30 a current value of the second power, and a control unit to
detect an abnormality of the first current measurement unit
based on the first current value and the second current
value.
4
Advantageous Effects of Invention
[0007] According to the present invention, the power
conversion device has an effect where it is possible to
detect an abnormality of a measuring 5 instrument that
measures an input current value.
Brief Description of Drawings
[0008] FIG. 1 is a diagram illustrating a configuration
10 example of a power conversion device.
FIG. 2 is a diagram illustrating a configuration
example of a control unit.
FIG. 3 is a flowchart illustrating an operation where
the control unit detects an abnormality of an input-current
15 sensor.
FIG. 4 is a diagram illustrating an example of a case
where a processing circuit included in the power conversion
device is constituted by a processor and a memory.
FIG. 5 is a diagram illustrating an example of a case
20 where a processing circuit included in the power conversion
device is constituted by dedicated hardware.
FIG. 6 is a diagram illustrating a configuration
example of a power conversion device to which a directcurrent
power is supplied.
25
Description of Embodiments
[0009] A power conversion device and an abnormality
detection method according to embodiments of the present
invention will be described in detail below with reference
30 to the accompanying drawings. The present invention is not
limited to the embodiments.
[0010] Embodiment.
FIG. 1 is a diagram illustrating a configuration
5
example of a power conversion device 4 according to an
embodiment of the present invention. While an example
where the power conversion device 4 is mounted on a railway
vehicle (not illustrated) is described below, it is merely
an example, and the power conversion 5 device 4 may be
mounted on a vehicle other than a railway vehicle. The
power conversion device 4 is connected to an overhead-wire
voltage sensor 2, a main transformer 3, a load 5, and a
display device 6. The overhead-wire voltage sensor 2, the
10 main transformer 3, the load 5, and the display device 6
are also mounted on the railway vehicle. An alternatingcurrent
overhead wire 1 supplies an alternating-current
power supplied from a substation (not illustrated) to the
main transformer 3. The overhead-wire voltage sensor 2 is
15 a measuring instrument that measures an alternating-current
voltage value of the alternating-current power supplied
from the alternating-current overhead wire 1 to the main
transformer 3, that is, an overhead-wire voltage value.
The main transformer 3 converts an overhead-wire voltage of
20 the alternating-current power supplied from the
alternating-current overhead wire 1 into a voltage at a
level at which the voltage can be used by the power
conversion device 4. A first alternating-current power
that is an alternating-current power having been voltage25
converted in the main transformer 3 is input to the power
conversion device 4 as an input power.
[0011] The power conversion device 4 outputs a second
alternating-current power that is a three-phase
alternating-current power having been converted from a
30 direct-current power in an inverter 16 described later to
the load 5 as an output power. That is, the power
conversion device 4 converts the first alternating-current
power input thereto into the second alternating-current
6
power and outputs the second alternating-current power.
The load 5 is an electrical device mounted on the railway
vehicle. The load 5 is, for example, a motor, an air
conditioner, or a compressor. When a control unit 18 of
the power conversion device 4 described 5 later has detected
an abnormality of an input-current sensor 12, the display
device 6 displays that, under control of the control unit
18, the input-current sensor 12 is abnormal. The display
device 6 is a monitor installed in a cab of the railway
10 vehicle, for example.
[0012] The configuration of the power conversion device
4 is described. The power conversion device 4 includes a
filter reactor 11, the input-current sensor 12, a converter
13, a direct-current voltage sensor 14, a filter capacitor
15 15, the inverter 16, an output-current sensor 17, and the
control unit 18.
[0013] The filter reactor 11 constitutes a filter
circuit along with the filter capacitor 15, and reduces a
rapid current change in the first alternating-current power.
20 The input-current sensor 12 is a measuring instrument that
measures a first current value that is a current value of
the first alternating-current power input from the main
transformer 3 to the power conversion device 4. The inputcurrent
sensor 12 is a first current measurement unit. The
25 converter 13 converts the first alternating-current power
input from the main transformer 3 to the power conversion
device 4 into a direct-current power. The configuration of
the converter 13 may be a general one and it is not limited
to any specific configuration. The direct-current voltage
30 sensor 14 is a measuring instrument that measures a directcurrent
voltage value of the direct-current power output
from the converter 13. The filter capacitor 15 removes
harmonic components generated in power conversion
7
processing performed by the converter 13 and the inverter
16 from the direct-current power. Further, the filter
capacitor 15 is charged by the direct-current power output
from the converter 13.
[0014] The inverter 16 converts a direct-5 current power
that is output from the converter 13 and with which the
filter capacitor 15 is charged into the second alternatingcurrent
power. The configuration of the inverter 16 may be
a general one and it is not limited to any specific
10 configuration. Here, the second alternating-current power
output from the inverter 16 is assumed to be a three-phase
alternating-current power. The output-current sensor 17 is
a measuring instrument that measures a second current value
that is a current value of the second alternating-current
15 power of each phase output from the inverter 16. The
output-current sensor 17 is a second current measurement
unit. It is assumed that the converter 13 and the inverter
16 collectively constitute a power converter. The control
unit 18 controls operations of the converter 13 and the
20 inverter 16 that constitute the power converter. The
control unit 18 also detects an abnormality of the inputcurrent
sensor 12 based on the first current value that is
a measurement result of the input-current sensor 12 and the
second current value that is a measurement result of the
25 output-current sensor 17. In the power conversion device 4,
configurations other than the configuration of the control
unit 18 are identical to configurations used in a general
power conversion device.
[0015] The configuration of the control unit 18 is
30 described. FIG. 2 is a diagram illustrating a
configuration example of the control unit 18 according to
the present embodiment. The control unit 18 includes an
A/D (Analog/Digital) conversion unit 21 and a control
8
calculation unit 22.
[0016] The A/D conversion unit 21 converts a measured
value obtained by measurement of each sensor from an analog
value into a digital value. Specifically, the A/D
conversion unit 21 converts each of the 5 measured values,
which are an overhead-wire voltage value measured by the
overhead-wire voltage sensor 2, an input current value
measured by the input-current sensor 12, a direct-current
voltage value measured by the direct-current voltage sensor
10 14, and an output current value measured by the outputcurrent
sensor 17 from an analog value, into a digital
value. While the output current value is represented with
a single line in FIG. 2, in practice, output current values
for three phases are input to the A/D conversion unit 21 as
15 illustrated in FIG. 1. Similarly, as for the output
current value output from the A/D conversion unit 21 to the
control calculation unit 22, in practice, output current
values for three phases are output from the A/D conversion
unit 21.
20 [0017] The control calculation unit 22 acquires each
measured value having been converted into a digital value
from the A/D conversion unit 21, and controls operations of
the power conversion device 4 based on each measured value.
The control calculation unit 22 includes a power-conversion
25 control unit 23, an abnormality detection unit 24, and a
transmission control unit 25.
[0018] The power-conversion control unit 23 controls
operations of the converter 13 and the inverter 16 by using
the overhead-wire voltage value, the input current value,
30 the direct-current voltage value, and the output current
value acquired from the A/D conversion unit 21. The powerconversion
control unit 23 monitors the state of an
alternating-current power supplied from the alternating9
current overhead wire 1, more specifically, the phase and
amplitude of an alternating-current voltage by using the
overhead-wire voltage value, and uses the monitored state
for control of the converter 13 and the inverter 16. The
power-conversion control unit 23 calculates 5 a target
current value of the input current value based on the
output current value in such a manner that an appropriate
amount of a direct-current power is input from the
converter 13 to the inverter 16 with respect to the amount
10 of an alternating-current power output from the inverter 16.
The power-conversion control unit 23 may calculate the
target current value of the input current value based on
the direct-current voltage value and the output current
value. The power-conversion control unit 23 controls the
15 operation of the converter 13 in such a manner that the
input current value becomes the target current value. The
method of controlling the converter 13 and the inverter 16
by the power-conversion control unit 23 may be a general
one and it is not limited to any specific method. In a
20 case where the converter 13 and the inverter 16 each
include a switching element, for example, the powerconversion
control unit 23 controls the operation of the
switching element included in each of the converter 13 and
the inverter 16.
25 [0019] The abnormality detection unit 24 detects an
abnormality of the input-current sensor 12 based on the
input current value and the output current value acquired
from the A/D conversion unit 21. Detailed operations of
the abnormality detection unit 24 are described later.
30 [0020] When an abnormality of the input-current sensor
12 is detected in the abnormality detection unit 24, the
transmission control unit 25 notifies the display device 6
that the input-current sensor 12 is abnormal. The
10
transmission control unit 25 causes the display device 6 to
display that the input-current sensor 12 is abnormal.
[0021] Next, there is described an operation of the
power conversion device 4, in which the control unit 18
detects an abnormality of the input-current 5 sensor 12. FIG.
3 is a flowchart illustrating an operation where the
control unit 18 according to the present embodiment detects
an abnormality of the input-current sensor 12. As for a
first threshold used in a determination process in the
10 operation illustrated in FIG. 3, it is permissible that the
abnormality detection unit 24 receives a parameter from a
user in advance, or calculates the parameter during the
operation. As for a second threshold, the abnormality
detection unit 24 receives a parameter from a user in
15 advance. Details of the first and second thresholds are
described later in detail.
[0022] First, in the control unit 18, the abnormality
detection unit 24 determines whether the converter 13 and
the inverter 16 are in operation (Step S1). In general,
20 when the converter 13 and the inverter 16 are in operation,
a control signal is input from the power-conversion control
unit 23 to the converter 13 and the inverter 16. The
abnormality detection unit 24 can determine whether the
converter 13 and the inverter 16 are in operation based on
25 the presence of the control signal from the powerconversion
control unit 23 to the converter 13 and the
inverter 16. Further, the abnormality detection unit 24
may determine whether the converter 13 and the inverter 16
are in operation based on the contents of an operation
30 instruction output from a cab (not illustrated) in a
railway vehicle to the control unit 18. When the converter
13 and the inverter 16 are not in operation (NO at Step S1),
the abnormality detection unit 24 returns to the process at
11
Step S1. When the converter 13 and the inverter 16 are in
operation (YES at Step S1), the abnormality detection unit
24 checks an output current value acquired from the A/D
conversion unit 21 (Step S2).
[0023] The abnormality detection 5 unit 24 determines
whether the acquired output current value exceeds the set
second threshold (Step S3). The second threshold is a
value for determining whether the second alternatingcurrent
power is output from the inverter 16 to the load 5.
10 The second threshold is a fixed value larger than "0" set
by a user or the like in advance. For example, the user
sets the second threshold based on the measurement accuracy
of the output-current sensor 17, while taking measurement
errors or the like into consideration. The abnormality
15 detection unit 24 compares each of the acquired output
current values for three phases and the second threshold
with each other. When there is no output current value
exceeding the second threshold (NO at Step S3), the
abnormality detection unit 24 returns to the process at
20 Step S2. When it is NO at Step S3, it means that the
second alternating-current power is not output to the load
5. Therefore, the load 5 is not in operation. When there
is one or more output current values exceeding the second
threshold (YES at Step S3), the abnormality detection unit
25 24 checks an input current value acquired from the A/D
conversion unit 21 (Step S4).
[0024] The abnormality detection unit 24 determines
whether the acquired input current value is smaller than
the set first threshold (Step S5). The first threshold is
30 a value for determining whether the first alternatingcurrent
power is input from the main transformer 3 to the
converter 13. The first threshold may be a fixed value set
in advance by a user or the like, or may be a calculated
12
value set by the abnormality detection unit 24 based on
calculation. The abnormality detection unit 24 calculates
a value that is in proportion to the magnitude of the
output current value or a target current value calculated
in the power-conversion control unit 5 23, based on the
output current value or the target current value and sets
the calculated value as the first threshold. Accordingly,
the abnormality detection unit 24 can set the first
threshold in accordance with the magnitude of the output
10 current value, so that it is possible to improve the
determination accuracy at Step S5 as compared with a case
where the first threshold is a fixed value. When
calculating the first threshold, the abnormality detection
unit 24 may use the latest output current value or the
15 target current value based on the latest output current
value. Further, because the control unit 18 repeats the
operation in the flowchart illustrated in FIG. 3, when
calculating the first threshold, the abnormality detection
unit 24 may use the output current value or the target
20 current value acquired in the previous operation. In a
case where the input current value becomes a certain
constant value when the input-current sensor 12 is abnormal,
setting the first threshold to a fixed value can reduce the
processing load of the abnormality detection unit 24 as
25 compared with a case where the first threshold is a
calculated value.
[0025] When the input current value is equal to or
larger than the first threshold (NO at Step S5), the
abnormality detection unit 24 returns to the process at
30 Step S1. When it is NO at Step S5, the input-current
sensor 12 is in a normal state. When the input current
value is smaller than the first threshold (YES at Step S5),
the abnormality detection unit 24 determines that the
13
input-current sensor 12 is abnormal (Step S6). Upon
detection of an abnormality of the input-current sensor 12,
the abnormality detection unit 24 notifies the powerconversion
control unit 23 and the transmission control
unit 25 that the input-current sensor 5 12 is abnormal.
[0026] When the abnormality detection unit 24 detects an
abnormality of the input-current sensor 12, the powerconversion
control unit 23 receives a notification from the
abnormality detection unit 24 and stops operations of the
10 converter 13 and the inverter 16 (Step S7). When the
abnormality detection unit 24 detects an abnormality of the
input-current sensor 12, the transmission control unit 25
receives the notification from the abnormality detection
unit 24 and notifies the display device 6 connected to the
15 power conversion device 4 that the input-current sensor 12
is abnormal. The transmission control unit 25 causes the
display device 6 to display that the input-current sensor
12 is abnormal (Step S8). The contents displayed on the
display device 6 may be a message indicating that the
20 input-current sensor 12 is abnormal or an error code.
[0027] A user can recognize that, by confirming the
displayed contents on the display device 6, the cause of
stopping the operations of the converter 13 and the
inverter 16 is an abnormality of the input-current sensor
25 12. The control unit 18 repeats the operation in the
flowchart illustrated in FIG. 3.
[0028] A hardware configuration of the power conversion
device 4 is described next. As described above, in the
power conversion device 4, configurations other than the
30 configuration of the control unit 18 are identical to
configurations used in a general power conversion device.
The control unit 18 is realized by a processing circuit.
That is, the power conversion device 4 includes a
14
processing circuit that can detect an abnormality of the
input-current sensor 12. The processing circuit may be a
processor that executes a program stored in a memory and
the memory, or may be dedicated hardware.
[0029] FIG. 4 is a diagram illustrating 5 an example of a
case where a processing circuit included in the power
conversion device 4 according to the present embodiment is
constituted by a processor and a memory. In a case where
the processing circuit is constituted by a processor 91 and
10 a memory 92, functions of the processing circuit of the
power conversion device 4 are realized by software,
firmware, or a combination of software and firmware. The
software or the firmware is described as a program and is
stored in the memory 92. The processing circuit realizes
15 the functions thereof by reading and executing the program
stored in the memory 92 by the processor 91. That is, the
processing circuit includes the memory 92 that stores
therein a program that causes detection of an abnormality
of the input-current sensor 12 to be consequently performed.
20 Further, such programs can be considered as elements that
cause a computer to perform the procedures and method of
the power conversion device 4.
[0030] The processor 91 may be a device such as a CPU
(Central Processing Unit), a processing device, an
25 arithmetic device, a microprocessor, a microcomputer, or a
DSP (Digital Signal Processor). The memory 92 corresponds
to, for example, a nonvolatile or volatile semiconductor
memory such as a RAM (Random Access Memory), a ROM (Read
Only Memory), a flash memory, an EPROM (Erasable
30 Programmable ROM), and an EEPROM® (Electrically EPROM), or
a device such as a magnetic disk, a flexible disk, an
optical disk, a compact disk, a MiniDisk, and a DVD
(Digital Versatile Disk).
15
[0031] FIG. 5 is a diagram illustrating an example of a
case where a processing circuit included in the power
conversion device 4 according to the present embodiment is
constituted by dedicated hardware. When the processing
circuit is constituted by dedicated hardware, 5 a processing
circuit 93 illustrated in FIG. 5 corresponds to, for
example, a single circuit, a composite circuit, a
programmed processor, a parallel-programmed processor, an
ASIC (Application Specific Integrated Circuit), an FPGA
10 (Field Programmable Gate Array), or a combination of these
elements. Each of the functions of the power conversion
device 4 may be realized by the processing circuit 93 for
each function, or these functions may be collectively
realized by the processing circuit 93.
15 [0032] As for the respective functions of the power
conversion device 4, it is possible to configure that some
parts of the functions are realized by dedicated hardware
and other parts thereof are realized by software or
firmware. In this manner, the processing circuit can
20 realize each function described above by dedicated hardware,
software, firmware, or a combinations of these elements.
[0033] Normally, the control unit 18 executes control in
such a manner that an input current value becomes a target
current value. Therefore, in a case where an abnormality
25 occurs in the input-current sensor 12 and the input current
value is smaller than the target current value, the control
unit 18 increases the target current value to increase the
input current value, so that there is a possibility that an
input overcurrent is generated. According to the present
30 embodiment, as described above, in the power conversion
device 4, when an output current value of an alternatingcurrent
power output from the inverter 16 is larger than
the second threshold and an input current value of an
16
alternating-current power input to the converter 13 is
smaller than the first threshold, the control unit 18
determines that the input-current sensor 12 having measured
the input current value is abnormal. Upon detection of an
abnormality of the input-current sensor 5 12, the control
unit 18 stops operations of the converter 13 and the
inverter 16 because the control unit 18 cannot accurately
control the converter 13 and the inverter 16. Accordingly,
in the power conversion device 4 according to the present
10 embodiment, it is possible to prevent an input overcurrent
from being input to the converter 13, thereby protecting
internal parts of the power conversion device 4. Further,
the control unit 18 causes the display device 6 to display
that the input-current sensor 12 is abnormal. A user who
15 has confirmed the contents of the display device 6 can
recognize the cause of stopping the operations of the
converter 13 and the inverter 16.
[0034] While a case in which an alternating-current
power is supplied to a railway vehicle from the
20 alternating-current overhead wire 1 has been described in
the present embodiment, this case is merely an example and
the application of the present invention is not limited
thereto. For example, the present invention can be also
applied to a case where a direct-current power is supplied
25 from a direct-current overhead wire to a railway vehicle.
FIG. 6 is a diagram illustrating a configuration example of
a power conversion device 4a according to the present
embodiment to which a direct-current power is supplied.
The power conversion device 4a is the power conversion
30 device 4 illustrated in FIG. 1 in which the input-current
sensor 12, the converter 13, the direct-current voltage
sensor 14, and the control unit 18 are omitted therefrom
and an input-current sensor 12a and a control unit 18a are
17
added thereto. In the power conversion device 4a, the
input-current sensor 12a measures a current value of a
direct-current power supplied from a direct-current
overhead wire 1a, that is, a direct current value as an
input current value. The control unit 5 18a detects an
abnormality of the input-current sensor 12a based on the
first current value that is a measurement result of the
input-current sensor 12a and the second current value that
is a measurement result of the output-current sensor 17.
10 The contents of the processing performed by the control
unit 18a are similar to the contents of the processing
performed by the control unit 18, and thus descriptions of
detailed configurations and operations of the control unit
18a are omitted. The direct-current power input to the
15 power conversion device 4a may be a direct-current power
after the voltage of the direct-current power supplied from
the direct-current overhead wire 1a is converted. The
power conversion device 4a converts the direct-current
power input thereto into an alternating-current power and
20 outputs the alternating-current power. That is, the
present invention can be applied to a power conversion
device that converts a first power input thereto into a
second power and outputs the second power. The first power
may be the first alternating-current power described above
25 or a direct-current power. The second power is the second
alternating-current power described above. The power
conversion device can detect an abnormality of an inputcurrent
sensor that measures an input current value, that
is, a direct current value by using an output current value
30 and the input current value.
[0035] The configurations described in the above
embodiment are only examples of the content of the present
invention. The configurations can be combined with other
18
well-known techniques, and part of each of the
configurations can be omitted or modified without departing
from the scope of the present invention.
Reference 5 Signs List
[0036] 1 alternating-current overhead wire, 1a directcurrent
overhead wire, 2 overhead-wire voltage sensor, 3
main transformer, 4, 4a power conversion device, 5 load,
6 display device, 11 filter reactor, 12, 12a input10
current sensor, 13 converter, 14 direct-current voltage
sensor, 15 filter capacitor, 16 inverter, 17 outputcurrent
sensor, 18, 18a control unit, 21 A/D conversion
unit, 22 control calculation unit, 23 power-conversion
control unit, 24 abnormality detection unit, 25
15 transmission control unit.
19
We Claim:
1. A power conversion device comprising:
a power converter to convert a first power into a
5 second power;
a first current measurement unit to measure a first
current value that is a current value of the first power;
a second current measurement unit to measure a second
current value that is a current value of the second power;
10 and
a control unit to detect an abnormality of the first
current measurement unit based on the first current value
and the second current value.
15 2. The power conversion device according to claim 1,
wherein
the first power is a first alternating-current power
and the second power is a second alternating-current power,
the power converter includes
20 a converter to convert the first alternating-current
power into a direct-current power, and
an inverter to convert the direct-current power into
the second alternating-current power, and
the control unit stops operations of the converter and
25 the inverter when an abnormality of the first current
measurement unit is detected.
3. The power conversion device according to claim 1 or 2,
wherein the control unit determines that the first current
30 measurement unit is abnormal when the first current value
is smaller than a first threshold and the second current
value is larger than a second threshold.
20
4. The power conversion device according to claim 3,
wherein the control unit calculates the first threshold
based on the second current value.
5. The power conversion device according 5 to claim 3,
wherein the first threshold is a fixed value.
6. The power conversion device according to any one of
claims 1 to 5, wherein the control unit causes a display
10 device connected to the power conversion device to display
that the first current measurement unit is abnormal when an
abnormality of the first current measurement unit is
detected.
15 7. An abnormality detection method comprising:
a power conversion step of converting a first power
into a second power by a power converter;
a first current measurement step of measuring a first
current value that is a current value of the first power by
20 a first current measurement unit;
a second current measurement step of measuring a
second current value that is a current value of the second
power by a second current measurement unit; and
an abnormality detection step of detecting an
25 abnormality of the first current measurement unit based on
the first current value and the second current value by a
control unit.
8. The abnormality detection method according to claim 7,
30 wherein
in a case where the first power is a first
alternating-current power and the second power is a second
alternating-current power, and the power converter includes
21
a converter and an inverter,
at the power conversion step,
the converter converts the first alternating-current
power into a direct-current power and the inverter converts
the direct-current power into the 5 second alternatingcurrent
power, and
the abnormality detection method further comprises a
control step of stopping operations of the converter and
the inverter when the control unit has detected an
10 abnormality of the first current measurement unit at the
abnormality detection step.
9. The abnormality detection method according to claim 7
or 8, wherein at the abnormality detection step, the
15 control unit determines that the first current measurement
unit is abnormal when the first current value is smaller
than a first threshold and the second current value is
larger than a second threshold.
20 10. The abnormality detection method according to claim 9,
wherein at the abnormality detection step, the control unit
calculates the first threshold based on the second current
value.
25 11. The abnormality detection method according to claim 9,
wherein the first threshold is a fixed value.
12. The abnormality detection method according to any one
of claims 7 to 11, comprising a display step at which the
30 control unit causes a display device to display that the
22
first current measurement unit is abnormal when the first
current measurement unit is determined to be abnormal.