1. A power conversion apparatus having at least one power conversion unit of a converter power conversion unit for converting AC power into voltage at plural potentials or an inverter power conversion unit for converting voltage at plural potentials into AC power, the apparatus comprising: current detectors for detecting a current flowing between the power conversion unit and a power supply or a loading device; and an abnormality determination device for determining abnormality of the current detector based on a value of ripple current contained in a detection value of the current detectors.

2. The power conversion apparatus according to claim 1, further comprising a memory unit for storing a reference value of ripple current assumed to be contained in the detection value of the current detector, wherein the abnormality determination device determines the abnormality of the current detector based on the reference value of the ripple current stored in the memory unit and the value of the ripple current contained in the detection value of the current detector. - 50 -

3. The power conversion apparatus according to claim 2, wherein the memory unit stores, as a reference value, a non-loaded reference value that is a reference value of the ripple current assumed to be contained in the detection value of the current detector upon operation of the power conversion unit under non-loaded conditions, and the abnormality determination device determines the abnormality of the current detector based on the value of the ripple current contained in the detection value of the current detector and the non-loaded reference value upon operation of the power conversion unit under non-loading conditions.

4. The power conversion apparatus according to any one of claims 1 to 3, comprising a plurality of the current detectors for detecting respective currents of plural phases flowing between the power conversion unit and the power supply or the loading device.

5. The power conversion apparatus according to claim 4, wherein the abnormality determination device determines that the power conversion unit is abnormal in a case where all of the detection values of the plural current detectors are zero or close to zero.

6. The power conversion apparatus according to claim - 51 - 4 or 5, wherein the abnormality determination device determines that a wiring connected to any one of current detectors is abnormal in a case where any one of the detection values of the plural current detectors is zero or close to zero.

7. The power conversion apparatus according to claim 2, wherein the abnormality determination device determines that the current detector is abnormal when the value of the ripple current contained in the detection value of the current detector deviates by more than a predetermined value from the reference value of the ripple current stored in the memory unit.

8. The power conversion apparatus according to claim 2, wherein the reference value of the ripple current stored in the memory unit is a reference value calculated based on the detection values of the current detector upon installation and operation of the power conversion apparatus, and the abnormality determination device determines that the current detector is abnormal in a case where the value of the ripple current contained in the detection value of the current detector deviates by more than a predetermined value from the reference value of the ripple current stored - 52 - in the memory unit.

9. The power conversion apparatus according to claim 2, wherein the abnormality determination device determines the abnormality in a case where an amended current value obtained by multiplying the value of the ripple current contained in the detection value by a coefficient in consideration of a fluctuation of a DC voltage by the power conversion unit deviates by more than a predetermined value from the reference value stored in the memory unit.

10. The power conversion apparatus according to claim 4, having a plurality of the current detectors for detecting respective currents of three phases flowing between the power conversion unit and the power supply or the loading device, further comprising an output estimation device for estimating a value of a current as a detection target of the current detector determined as abnormal based on the detection values of the current detectors of two phases other than the phase as the detection target of the current detector determined as abnormal.

11. The power conversion apparatus according to claim 1, having a plurality of the current detectors for detecting respective currents of three phases flowing between the power conversion unit and the power supply or the loading device, - 53 - wherein the abnormality determination device determines an abnormal current detector among the plurality of current detectors based on the differential value between a value of the ripple current contained in the current value of a certain phase calculated from the value of the ripple current contained in the current value of other two phases and a value of the ripple current contained in the detection value of the certain phase, and the value of the ripple current contained in the detection value of each of phases.

12. The power conversion apparatus according to claim 11 further comprising an output estimation device for estimating a value of a current as a detection target of the current detector which has been determined as abnormal based on the detection values of the current detectors of two phases other than the phase as the detection target of the current detector determined as abnormal.

13. The power conversion apparatus according to any one of claims 1 to 12, wherein the abnormality determination device displays information for abnormality on a display device upon determination of the occurrence of abnormality.

14. The power conversion apparatus according to claim 13, wherein the abnormality determination device stores a history of the detection value by the current detector, - 54 - predicts the period till generation of the abnormality in the current detector based on the history of the detection value, and displays the result of the prediction on the display device.

15. An abnormality detection method by a power conversion apparatus having at least one power conversion unit of a converter power conversion unit for converting AC power to DC power at plural potentials and an inverter power conversion unit for converting voltage at plural potentials into AC power, the method comprising: detecting a current flowing between the power conversion unit and a power supply or a loading device by a current detector; and determining the abnormality of the current detector based on the value of the ripple current contained in the detection value of the current detector.

BACKGROUND
[0001]
The present invention relates to a power conversion
apparatus having at least one power conversion unit of a
converter conversion unit and an inverter conversion unit,
and an abnormality detection method for detecting
abnormality of the power conversion apparatus and, more
in particular, to a technique of detecting abnormality of
a current detector in the power conversion apparatus.
[0002]
Power conversion apparatus of converting the power
from AC power supply into variable voltages and variable
frequency power has been known. The power conversion
apparatus has a current detector that detects a current
flowing between a power converter and a power supply, and
it controls current such that the current is at a
predetermined value. And the power conversion apparatus
has a current detector that detects a current flowing
between a power converter and an electric motor, and it
controls current such that the current is at a predetermined
value.
- 3 -
[0003]
For example, as a technique for confirming the
normality of a current detector that detects a current
flowing between a power converter and an electric motor,
a technique of performing single phase DC excitation and
judging the abnormality due to behavior of a current flowing
upon single phase excitation has been known (for example,
refer to Japanese Unexamined Patent Application
Publication No. 2014-090611).
SUMMARY
[0005]
A current detector for detecting a current flowing
between a power converter and an electric motor and a
current detector for detecting a current flowing between
the power converter and a power supply are essential for
controlling the current of the power conversion apparatus.
Abnormality of the current detector may possibly make
system operation unstable and, in the worst case, bring
about unexpected system breakdown, to cause heavy damages.
[0006]
Japanese Unexamined Patent Application Publication
No. 2014-090611 shows a technique of performing single
phase DC excitation for confirming the normality of a
- 4 -
current detector that measures a current flowing between
a power conversion apparatus and an electric motor and
determines abnormality due to behavior of the current
flowing thereupon but does not disclose a technique of
determining the abnormality of a current detector for
measuring the current flowing between the power supply and
the power conversion apparatus.
[0007]
Further, there is also a need for other techniques
of confirming the normality of the current detector that
measures a current flowing between the power conversion
apparatus and a load device.
[0008]
The present invention has been accomplished in view
of the foregoing situations and it intends to provide a
technique capable of appropriately detecting abnormality
of a current detector in a power conversion apparatus.
[0009]
For attaining the foregoing purpose, a power
conversion apparatus in one aspect according the present
invention provides a power conversion apparatus including
current detectors for detecting a current flowing between
the power conversion unit and a power supply or a loading
device, and an abnormality determination device for
- 5 -
determining abnormality of the current detectors based on
a value of ripple current contained in detection values
of the current detectors.
[0010]
According to the present invention, abnormality of
the current detector in the power conversion apparatus can
be detected appropriately.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
Fig. 1 is an entire configurational view of a power
conversion apparatus according to a first embodiment;
Fig. 2A is a diagram explaining data of values of
ripple current (reference data) assumed to be contained
in a current value detected by a current detector in the
first embodiment;
Fig. 2B is a diagram explaining data of current values
of ripple current contained in current values detected by
the current detectors in the first embodiment;
Fig. 3 is a flow chart of an abnormality determination
processing in the first embodiment;
Fig. 4A is a diagram showing values of ripple current
contained in current values detected by respective current
detectors for detecting three-phase AC current in the first
- 6 -
embodiment;
Fig. 4B is a diagram showing data of differential
values between values of ripple current corresponding to
each of phases estimated based on current values detected
by current detectors of other plural phases and the
detection values of each phase, for each of phases in a
case where each of the current detectors is normal in the
first embodiment;
Fig. 4C is a diagram showing data of differential
values between values of ripple current corresponding to
each of phases estimated based on current values detected
by current detectors of other plural phases and the
detection values of each phase, for each of phases in a
case where the current detectors of the R phase are abnormal
in the first embodiment;
Fig. 4D is a diagram showing data of differential
values between values of ripple current corresponding to
each of phases estimated based on current values detected
by current detectors of other plural phases and the
detection values of each phase, for each of phases in a
case where the current detectors of the S phase are abnormal
in the first embodiment;
Fig. 4E is a diagram showing data of differential
values between values of ripple current corresponding to
- 7 -
each of phases estimated based on current values detected
by current detectors of other plural phases and the
detection values of each phase, for each of phases in a
case where the current detectors of the T phase are abnormal
in the first embodiment;
Fig. 5 is an entire configurational view of the power
conversion apparatus according to a second embodiment;
Fig. 6 is an entire configurational view of the power
conversion apparatus according to a third embodiment; and
Fig. 7 is a partial configurational view of the power
conversion apparatus including an output estimation device
according to the third embodiment.
DETAILED DESCRIPTION
[0012]
Several preferred embodiments are to be described
with reference to the drawings. Preferred embodiments to
be described below are not restrictive for the inventions
according to claims, and various elements and combinations
thereof explained in the preferred embodiments are not
always essential to the solution of the problems of the
present inventions.
[0013]
First, a power conversion apparatus according to the
- 8 -
first embodiment is to be described.
[0014]
Fig. 1 is an entire configurational view of a power
conversion apparatus according to a first embodiment.
[0015]
A power conversion apparatus 100 has an AC power
supply 1 as an example of a power supply, a converter unit
(also referred to simply as a converter) 2 for converting
an AC power from the AC power supply 1 into a DC power,
an inverter unit (also referred to simply as an inverter)
3 for converting the DC power outputted from the converter
unit 2 into a desired AC power, an electric motor 4 as an
example of a loading device driven by the AC power outputted
from the inverter unit 3, a converter control device 5 for
controlling the converter unit 2, and an inverter control
device 6 for controlling the inverter unit 3.
[0016]
The converter unit 2 is a so-called three-level
converter and converts an AC power into a DC power at a
positive potential (first potential) level, a neutral point
(zero) potential (second potential) level and a negative
potential (third potential) level. The inverter unit 3 is
a so-called three-level inverter and converts a DC power
at a positive potential (1st potential) level, a neutral
- 9 -
point (zero) potential (2nd potential) level and a negative
potential (3rd potential) level into an AC power for the
electric motor 4. The positive potential levels of the
converter unit 2 and the inverter unit 3 are connected by
way of a P wiring 40, the neutral potential levels are
connected by way of a C wiring 41, and the negative potential
levels are connected by way of a N wiring 42.
[0017]
The converter unit 2 has, for each of three phases,
a converter power conversion unit 21 as an example of the
power conversion unit, a converter P side smoothing
capacitor 22 and a converter N side smoothing capacitor
23 for suppressing fluctuation of a DC voltage, a converter
P side DC voltage detector 24 for measuring an
inter-terminal voltage of the converter P side smoothing
capacitor 22 and a converter N side DC voltage detector
25 for measuring inter-terminal voltage of the converter
N side smoothing capacitor 23. Fig. 1 shows a
configuration of the converter unit 2 for one phase.
[0018]
The inverter unit 3 has, for each of three phases,
an inverter power conversion unit 31 as an example of a
power conversion unit, an inverter P side smoothing
capacitor 32, and an inverter N side smoothing capacitor
- 10 -
33. Fig. 1 shows a configuration of the inverter unit 3
for one phase.
[0019]
The converter control device 5 controls the converter
power conversion unit 21 such that the converted DC power
is at a desired value. The inverter control device 6
controls the inverter power conversion unit 31 such that
the output torque and the speed of the electric motor 4
satisfy desired characteristics.
[0020]
The converter unit 2 further has an R phase current
detector 26 that detects and outputs an R phase output
current in three phases of the converter unit 2 (between
the converter unit 2 and the AC power supply 1) (hereinafter
referred to simply as a current detector 26), an S phase
current detector 27 that detects and outputs an S phase
output current in three phases of the converter unit 2
(hereinafter referred to simply as a current detector 27),
and a T phase output current detector 28 that detects and
outputs a T phase current in three phases of the converter
unit 2 (hereinafter referred to simply as a current detector
28). The inverter unit 3 further has a U phase current
detector 34 that detects and outputs a U phase output
current in three phases of the inverter unit 3 (between
- 11 -
the inverter unit 3 and electric motor 4) (hereinafter
referred to simply as a current detector 34), a V phase
current detector 35 that detects and outputs a V phase
output current in the three phases of the inverter unit
3 (hereinafter referred to simply as a current detector
35), and a W phase current detector 36 that detects and
outputs a W phase output current in three phases of the
inverter unit 3 (hereinafter referred to simply as a current
detector 36). The power conversion apparatus 100 further
has a speed detector 7 directly coupled to the electric
motor 4 for detecting and outputting the speed of the
electric motor 4.
[0021]
Signals of detection values detected by the current
detectors 26, 27, and 28, and the DC voltage detectors 24
and 25 (output signals) are inputted to the converter
control device 5. The converter control device 5 performs
various operation processing based on the inputted
detection values and outputs signals for controlling the
converter power conversion unit 21.
[0022]
Signals of detection values detected by the current
detectors 34, 35, and 36, and the speed detector 7 (output
signals) are inputted to the inverter control device 6.
- 12 -
The inverter control device 6 performs various operation
processing based on the inputted detection values and
outputs signals for controlling the inverter power
conversion unit 31.
[0023]
The converter control device 5 has a DC voltage
instruction generator 51, a DC voltage controller 52, a
current controller 53, and a pulse generator 54.
[0024]
The DC voltage instruction generator 51 outputs a DC
voltage instruction value showing a voltage value of the
DC voltage to be outputted from the converter unit 2 to
the DC voltage controller 52.
[0025]
The DC voltage controller 52 calculates a converter
output current instruction value based on the DC voltage
instruction value inputted from the DC voltage instruction
generator 51 and the detection values of the DC voltage
inputted from the DC voltage detectors 24 and 25 and outputs
the calculated value to the current controller 53.
Specifically, the DC voltage controller 52 calculates the
converter output current instruction value such that the
total value of the DC voltage detection values inputted
respectively from the DC voltage detectors 24 and 25 is
- 13 -
aligned with the DC voltage instruction value.
[0026]
The current controller 53 calculates the converter
voltage instruction value such that the converter output
current detection values outputted from the current
detectors 26, 27, and 28 are aligned with the converter
output current instruction values inputted from the DC
voltage controller 52 and outputs them to the pulse
generator 54.
[0027]
The pulse generator 54 calculates a pulse signal for
on-off control of each of switching elements of the
converter power conversion unit 21 such that the output
voltage by the converter power conversion unit 21 is aligned
with the converter output voltage instruction value
inputted from the current controller 53 and outputs the
pulse signal to the converter power conversion unit 21.
[0028]
The inverter control device 6 has a speed instruction
generator 61, a speed controller 62, a current controller
63, and a pulse generator 64.
[0029]
The speed instruction generator 61 outputs a speed
instruction value showing the speed of operating the
- 14 -
electric motor 4 to the speed controller 62.
[0030]
The speed controller 62 calculates an inverter output
current instruction value such that the speed detection
value inputted from the speed detector 7 is aligned with
the speed instruction value inputted from the speed
instruction generator 61 and outputs an inverter output
current instruction value to the current controller 63.
[0031]
The current controller 63 calculates the inverter
voltage instruction value such that the inverter output
current detection values inputted from the current
detectors 34, 35 and 36 are aligned with the inverter output
current instruction value inputted from the speed
controller 62 and outputs them to the pulse generator 64.
[0032]
The pulse generator 64 calculates pulse signals for
on-off control of each of the switching elements in the
inverter power conversion unit 31 such that the output
voltage by the inverter power conversion unit 31 is aligned
with the inverter output voltage instruction value inputted
from the current controller 63 and outputs the pulse signal
to the inverter power conversion unit 31.
[0033]
- 15 -
Then, the configuration relevant to the abnormality
determination in the power conversion apparatus 100 is to
be described.
[0034]
The power conversion apparatus 100 has a converter
side abnormality determination device 71, an inverter side
abnormality determination device 72 and a display device
73.
[0035]
The display device 73 is, for example, a liquid
crystal display capable of displaying information and it
displays various information.
[0036]
The converter side abnormality determination device
71 has a memory 71a (storage unit). The memory 71a stores
data (ripple current data: reference data) relating to
values of a ripple current (standard value: reference
value) assumed to be formed in the current values upon
switching by the converter power conversion unit 21. The
reference data can be calculated based on pulse conditions
in the converter unit 2 and the impedance value on the side
of the AC power supply 1. Calculated reference data may
also be stored in the memory 71a.
[0037]
- 16 -
The converter side abnormality determination device
71 compares the current values(detection values) inputted
from the current detectors 26, 27, and 28 and the reference
data stored in the memory 71a (storage unit) and determines
whether the abnormality is present or not in the current
detectors 26,27, and 28. For example, the converter side
abnormality determination device 71 extracts the values
of the ripple current from the detection values of the
current detectors 26, 27, and 28 and, if an average value
thereof deviates from the reference value by more than a
predetermined threshold value, determines that the current
detector detecting the abnormal detection value is abnormal.
For example, as a method of extracting values of the ripple
current from the detection values of the current detectors
26, 27, and 28, a filtration method of extracting only the
ripple current relative to the detection values can be
utilized.
[0038]
Upon detection of an abnormal current detector, the
converter side abnormality determination device 71
displays abnormal information (for example, information
capable of specifying the abnormal current detector (for
example, device number)) and a message that recommends
inspection, replacement, etc. on the display 73. The
- 17 -
converter side abnormality determination device 71 may also
be configured by executing a program accommodated in the
memory by an unillustrated processor.
[0039]
The inverter side abnormality determination device
72 has a memory 72a (storage unit). The memory 72a stores
data (ripple current data: reference data) relating to
values of ripple current (standard value: reference data)
assumed to be formed in the current values upon switching
by the inverter power conversion unit 31. The reference
data can be calculated based on the pulse conditions in
the inverter unit 3 and the impedance values on the side
of the electric motor 4. Calculated reference data may
also be stored in the memory 72a.
[0040]
The inverter side abnormality determination device
72 compares the current values(detection values) inputted
from the current detectors 34, 35, and 36 and the reference
data stored in the memory 72a (storage unit) and determines
whether the abnormality is present or not in the current
detectors 34, 35, and 36. For example, the inverter side
determination device 72 extracts values of the ripple
current from the detection values of the current detector
34, 35, and 36 and, if an average value thereof deviates
- 18 -
from the reference value by more than a predetermined
threshold value, determines that the current detector
detecting the abnormal detection value is abnormal. For
example, as a method of extracting the values of the ripple
current from the detection values of the current detectors
34, 35, and 36, a filtration method of extracting only the
ripple current relative to the detection value can be
utilized.
[0041]
Upon detection of an abnormal current detector, the
inverter side abnormality determination device 72 displays
abnormal information (for example, information capable of
specifying the abnormal current detector (for example,
device number) and a message recommending inspection,
replacement, etc. on the display device 73. The inverter
side abnormality determination device 72 may also be
configured by executing a program accommodated in the
memory by an unillustrated processor.
[0042]
Then, abnormality determination by the converter
side abnormality determination device 71 according to the
first embodiment is to be described specifically. This is
also applicable to the abnormality determination by the
inverter side abnormality determination device 72.
- 19 -
[0043]
Fig. 2A is a diagram for explaining data (reference
data) of values of ripple current assumed to be contained
in the current values detected by the current detectors
in the first embodiment and Fig. 2B is a diagram for
explaining data of values of ripple current contained in
the current value detected by the current detectors in the
first embodiment. Fig. 2B shows an example in which the
current detector 28 for detecting the T-phase current is
abnormal.
[0044]
As shown in Fig. 2A, in a case where current detectors
26, 27, 28 are normal, the data (reference data) of the
values of ripple current assumed to be obtained from current
values detected from the current detectors are as shown
in (a-1), (a-2), and (a-3) respectively. As described
above, the reference data are stored in the memory 71a.
[0045]
In a case where the abnormality is not present in the
current detector, the value of the ripple current contained
in the detection value of the current detector at each time
point is aligned or approximately aligned with the value
of the reference data at each time point. On the other hand,
in a case where the abnormality is present in the current
- 20 -
detector, the value of the ripple current contained in the
current value detected by the abnormal current detector
is as shown in (b-3) of Fig. 2B to cause deviation relative
to the corresponding reference data ((a-3) of Fig. 2A, in
this example).
[0046]
Then, the converter side abnormality determination
device 71 determines whether the value of the ripple current
contained in the detection value of the three current
detectors 26, 27, and 28 (detection values) deviate or not
by more than a predetermined threshold value from the value
of the ripple current of the reference data (reference
value). In a case where a detection value deviates by more
than a predetermined threshold value from a reference value,
it is determined that the current detector detecting such
an abnormal detection value is abnormal and displays
information that the current detector is abnormal and a
message of recommending checking and replacement of the
current detector on the display 73.
[0047]
As a method of specifying the value of the ripple
current contained in the detection value of the current
detector, a method of extracting only the value of the
ripple current from the detection value by using filtration
- 21 -
is employed. There is also the following method. For
example, in a case where the converter unit 2 is in a
non-loaded state, only the ripple current flows between
the converter unit 2 and the AC power supply 1 and the
detection value detected from each of the current detectors
26, 27, and 28 shows the value of the ripple current.
Therefore, it is adapted, for example, to determine the
abnormality of the current detector described above in a
standby state(non-loaded state) after initial charging of
the capacitors (22, 23, 32, 33) necessary for operation,
and there is no requirement of extracting the values of
the ripple current from the detection value of the current
detector and the abnormality of the current detector can
be determined easily by use the detection value of the
current detector, to enables early abnormality response
before starting actual operation. In the same manner, in
a case where the inverter unit 3 is in a non-loaded state
(upon starting excitation (DC excitation under non-load)),
a current comprising a ripple current superposing on a DC
current flows between the inverter unit 3 and the electric
motor 4 and the detection value detected from each of the
current detectors 34, 35, and 36 shows the current value
of the ripple current by subtracting a DC component.
Therefore, it is adapted, for example, to determine the
- 22 -
abnormality of the current detector described above in this
state, and the abnormality of the current detector can be
determined by easy extraction of the value of the ripple
current from the detection value of the current detector,
to enable early abnormality response before starting the
actual operation. In a case of processing in the
non-loaded state, it is necessary to store reference data
containing reference values (reference value upon
non-loaded state) of the ripple current corresponding to
the non-load state in the memory 71a (memory 72a).
[0048]
In Fig. 2A, the values of time series ripple current
(current waveform) are used as the reference data of the
values of the ripple current and compared with the values
of the ripple current contained in the time series detection
values of the current detection values (ripple current
waveform). However, the present invention is not
restricted only to such an embodiment, but the abnormality
of the current detector may also be determined by using
the value of the ripple current under predetermined pulse
conditions as the reference values and comparing them with
a value obtained by predetermined processing to the value
of the ripple current contained in the detection value of
the current detector (for example, filtration by absolute
- 23 -
value expression or averaging).
[0049]
Even if the value of the ripple current contained in
the detection value of the current detector deviates from
the reference value by more than a predetermined threshold
value, this may not always mean that the current detector
is abnormal. Then, the converter side abnormality
determination device 71 according to this embodiment
performs abnormality determination processing shown below
in order to reduce the risk of erroneous determination that
the current detector is abnormal by other factors than those
of current detector abnormality.
[0050]
Fig. 3 is a flow chart of an abnormality determination
processing according to the first embodiment. The
abnormality determination processing is executed during
driving of the power conversion apparatus 100 by the
converter side abnormality determination device 71 and the
inverter side abnormality determination device 72
respectively. The following explanation is to be
described below mainly for the abnormality determination
processing of the converter side abnormality determination
device 71. The processing by the inverter side abnormality
determination device 72 is to be described only for the
- 24 -
points different from those of the converter side device
71 in corresponding brackets.
[0051]
The converter side abnormality determination device
71 [inverter side abnormality determination device 72]
determines whether all of the detection values of the three
current detectors 26, 27, and 28 [current detectors 34,
35, and 36] are zero (or close to zero) or not (step S11).
In this embodiment, the converter side abnormality
determination device 71 [inverter side abnormality
determination device 72] determines whether all of
detection values of the three current detectors 26, 27,
and 28 [current detectors 34, 35, and 36] are zero or not,
that is, whether the ripple current components are present
or not.
[0052]
Since the abnormality determination processing is
performed during driving of the power conversion apparatus
100, if the current detectors 26, 27, and 28 [current
detectors 34, 35, and 36] are normal, the detection values
of the current detectors 26, 27, and 27 [current detectors
34, 35, and 36] contain ripple current. Accordingly, in
a case where all of the detection values of the three current
detectors 26, 27, and 28 [current detectors 34, 35, and
- 25 -
36] are zero (Yes, in step S11), since this may possibly
indicate abnormality, for example, that the converter power
conversion unit 21 [inverter power conversion unit 31] is
abnormal, the converter side abnormality determination
device 71 [inverter side abnormality determination device
72] determines that the converter power conversion unit
21 [inverter power conversion unit 31] is abnormal,
displays information that the power conversion unit is
abnormal (“power conversion unit abnormality”) on the
display 73 (step: S12), and proceeds the processing step
to S19. While this embodiment determines the abnormality
of the converter power conversion unit 21 depending on the
presence or absence of the ripple current component, the
abnormality of the power conversion unit may also be
determined, for example, in a case where current flowing
upon driving the converter power conversion unit 21 after
initial charging in the converter unit 2 is not detected
in the three current detectors 26, 27 and 28 and all of
current values are zero.
[0053]
In the processing described above, while the
abnormality of the inverter power inversion unit 31 is
determined depending on the presence or absence of the
ripple current component, the abnormality of the power
- 26 -
conversion unit may be determined also in a case where
currents flowing upon driving the inverter power conversion
unit 31 for starting excitation on the inverter unit 3 side
(in a state of flowing an excitation current upon driving
the electric motor 4) are not detected in the three current
detectors 34, 35, and 36 and all of them are zero.
[0054]
On the other hand, in a case where not all of the
detection values of the three current detectors 26, 27,
and 28 [current detectors 34, 35, and 36] are not zero (or
close to zero) (No, in step S11), the converter side
abnormality determination device 71 [inverter side
abnormality determination device 72] determines whether
any of three current detectors 26, 27, and 28 [current
detectors 34, 35, and 36] contains zero or not (step S13).
[0055]
As a result, for example, in a case where the
detection values zero is present in any one of the three
current detectors 26. 27, and 28 [current detectors 34,
35, and 36] (Yes, in step S13), since there may be possibly
abnormality caused by disconnection and slack of loops
(current detection loop: wiring) for current detection
utilized in the current detector, the converter side
abnormality determination device 71 [inverter side
- 27 -
abnormality detection device 72] determines that the
current detection loop is abnormal, displays information
showing abnormality in the current detection loop (“current
detection loop abnormality”) on the display 73 (step S14),
and proceeds the processing step to S19. In the same manner
as in the step S11, abnormality may also be determined
depending on the presence or absence of the ripple current
component, in a state of driving the converter power
conversion unit 21 depending on the presence or absence
of the current, after initial charging on the side of the
converter unit 2, or in a state of driving the inverter
power conversion unit 31 for the state of excitation on
the side of the inverter unit 3.
[0056]
On the other hand, in a case where none of the three
current detectors 26, 27, and 28 [current detectors 34,
35, and 36] indicates zero (No, in step S13), the converter
side abnormality determination device 71 [inverter side
abnormality determination device 72] compares the value
of the ripple current contained in the detection value of
the three current detectors 26, 27, and 28 [current
detectors 34, 35, and 36] with the value of the ripple
current of the reference data (reference value), and
determines whether a deviation larger than a predetermined
- 28 -
threshold value is present or not (step S15).
[0057]
As a result, in a case where a deviation larger than
the predetermined threshold value is present between the
reference value and the detection value (Yes, in step S15),
the converter side abnormality determination device 71
[inverter side abnormality determination device 72]
determines that a current detector corresponding to a
detection value containing a deviation larger than a
predetermined threshold value is abnormal and displays the
information showing that the current detector is abnormal
(“current detector abnormality”) on the display device 73
(step S16) and proceeds the processing to the step S19.
[0058]
In the step S19, the converter side abnormality
determination device 71 [inverter side abnormality
determination device 72] displays a description that “check
and replace abnormal part” on the display 73.
[0059]
On the other hand, in a case where only the deviation
smaller than a predetermined threshold value is present
between the reference value and the detection value (No,
in step S15), since this means that each of the current
detectors 26, 27, and 28 [current detectors 34, 35, and
- 29 -
36] is not abnormal, the converter side abnormality
determination device 71 [inverter side abnormality
determination device 72] ends the abnormality
determination processing.
[0060]
As has been described above, since the power
conversion apparatus 100 according to the first embodiment
is adapted to determine the abnormality of the current
detector based on the values of the ripple current contained
in the output of the current detectors (detection value)
and display the recommendation of checking and replacement
of the abnormal current detector, this enables the current
detector to be checked and replaced before starting actual
operation.
[0061]
In the first embodiment described above, for example,
in a case where previously calculated data are used as the
reference data, conditions assumed upon previous
calculation and conditions in an actual place of locating
the power conversion apparatus 100 may possibly be
different. In such a case, if previously calculated
reference data are used, there may be a risk of committing
an error in the abnormality determination of the current
detector due to the error of the reference data.
- 30 -
[0062]
As a countermeasure, for example, the data for the
values of the ripple current formed in the detection value
from each of the current detectors also may be acquired
by driving the power conversion apparatus 100 at a point
of time capable of ensuring that the detection value of
the power conversion apparatus 100 is normal (for example,
upon initial setting (installation), etc. of the power
conversion apparatus 100) and the data may be stored as
the reference data in the memory unit 71a (72a). In this
way, the reference data can be adaptable to the actual state
of using the power conversion apparatus 100, thereby
capable of reducing the risk of erroneous determination
the current detector abnormality.
[0063]
Further, since the value of the ripple current
contained in the detection value detected from the current
detector fluctuates under the effect of the DC voltage of
the power conversion apparatus 100, the data of the current
value (amended current value) amended by multiplying a
coefficient in consideration of the fluctuation of the DC
voltage (amended ripple current values) to the value of
the ripple current contained in the detection value may
also be compared with the reference data. This can reduce
- 31 -
the risk of erroneous determination under the effect of
the fluctuation of the DC voltage.
[0064]
Further, while the abnormality of the current
detector is determined by comparison between the reference
data and the values of the ripple current contained in the
detection values of the respective current detectors 26,
27 and 28 (current detectors 34, 35, and 36) in the first
embodiment described above, the present invention is not
restricted only to such an embodiment but the abnormality
may also be determined, for example, by using and comparing
values obtained from the detection values of the three
current detectors 26, 27, and 28 (current detectors 34,
35, and 36] and comparing them with each other as shown
below.
[0065]
The method of determining the abnormality by mutual
comparison is to be described below. The method of
determining the abnormality by mutual comparison utilizes
that the sum of the current values for three phases is zero,
and the converter side abnormality determination device
71 (inverter side abnormality determination device 72)
determines the abnormality by mutually comparing data
between a value of ripple current contained in the current
- 32 -
value of a certain phase estimated from the value of the
ripple current contained in the current value of other two
phases (calculated value) and a value of the ripple current
contained in the detection value of the certain phase
(detection value) and the value of the ripple current
contained in the detection value of each of the phases.
[0066]
The method is to be described more specifically in
an example in which the converter unit 2 is in a non-loaded
state. In a case where the converter unit 2 is in the
non-loaded state, the detection value from each of the
current detectors 26, 27, 28 corresponds to the value of
the ripple current.
[0067]
Assuming the true values of the three-phase current
of the converter unit 2 as Ir, Is, and It, and the detection
values by the respective current detectors 26, 27, and 28
as Ird, Isd, and Itd. Further, it is assumed, for example,
that the abnormality is present in the detection value of
the T phase current detector 28 and Itd = It + Itd is
detected as an addition sum of the true value It and the
error Itd.
As has been described above, since the sum of the
three phase currents is zero, the converter side
- 33 -
abnormality determination device 71 prepares reference
data of each phase by subtracting the sum of the detection
values of other two phases from zero, and detects an
abnormal error by comparison between the reference data
of each phase and the detection value of the corresponding
phase (for example, by taking a difference). Then, the
converter side abnormality determination device 71
determines the presence or absence of the abnormality in
the current detector based on the abnormal error.
[0068]
Specifically, the reference data of the R phase: Irdh
is as shown in the formula (1), the reference data of the
S phase: Isdh is as shown in the formula (2) and the
reference data of the T phase: Itdh is as shown in the
formula (3).
Irdh=0-(Isd+Itd)=0-(Is+It+Itd)=Ir-Itd ----- (1)
Isdh=0-(Ird+Itd)=0-(Ir+It+Itd)=Is-Itd ----- (2)
Itdh=0-(Ird+Isd)=0-(Ir+Is)=It ----- (3)
[0069]
Referring to the differential value between the
detection value of each phase and the reference data, it
is Ird-Irdh = Ir-(Ir-Itd) = Itd for the R phase, Isd-Isdh
= Is-(Is-Itd) = Itd for the S phase, and Itd-Itdh =
It+Itd-It = Itd for the T phase, and an abnormality
- 34 -
component(Itd) is calculated for all of the phases.
[0070]
In a case where all of the current detectors are
normal, since Itd is zero, the differential value for each
of the phases is zero or close to zero. Accordingly,
presence or absence of the abnormality of the current
detector can be determined by judging whether the
differential value for all of the phases is within a range
of the predetermined threshold value or not.
[0071]
Then, specific examples of the value of the ripple
current, state of the current detector, and the
differential value of each of the phases are to be
described.
[0072]
Fig. 4A is a diagram showing values of ripple current
contained in current values detected by respective current
detectors for detecting AC current of three phases in the
first embodiment. Fig. 4B is a diagram showing, for each
of the phases in a case where each of the current detectors
is normal in the first embodiment, data of differential
values between the value of the ripple current
corresponding to each of the phases estimated based on the
current values detected by the current detectors of other
- 35 -
plural phases and the detection value for each of the phases.
Fig. 4C is a diagram showing, for each of phases in a case
where the R phase current detector is abnormal in the first
embodiment, data of differential values between the values
of the ripple current corresponding to each of the phases
estimated based on the current values detected by the
current detectors of other plural phases and detection
values of each for phases. Fig. 4D is a diagram showing,
for each of phases in a case where the S phase current
detector is abnormal in the first embodiment, data of
differential values between the values of the ripple
current corresponding to each of the phases estimated based
on the current values detected by the current detectors
of other plural phases and detection values for each of
phases. Fig. 4E is a diagram showing, for each of phases
in a case where the T phase current detector is abnormal
in the first embodiment, data of differential values
between the values of the ripple current corresponding to
each of the phases estimated based on the current values
detected by the current detectors of other plural phases
and detection values for each of phases.
[0073]
For example, as shown in Fig. 4A, in a case where all
of the current detectors 26, 27, and 28 are normal, the
- 36 -
value of the ripple current in the R phase is as shown in
(a-1), the value of the ripple current in the S phase is
as shown in (a-2) and the value of the ripple current in
the T phase is as shown in (a-3).
[0074]
In a case where all of the current detectors 26, 27,
and 28 are normal, the differential values for all of the
phases are always zero (or close to zero) as shown in (b-1),
(b-2), and (b-3) of Fig. 4B.
[0075]
On the other hand, in a case where the R phase current
detector 26 is abnormal (for example, gain failure is
assumed in the current detector 26), the differential
values for all of the phases contain values deviated from
zero as shown in (c-1), (c-2), and (c-3) of Fig. 4C and
it can be seen that any one of the current detectors is
abnormal. Further, the differential value data for each
of the phases provide identical waveforms as shown in (c-1),
(c-2), and (c-3) (similar waveforms in which temporal
variation direction is identical). It can be seen that the
waveform is identical with the waveform (a-1) detected by
the abnormal current detector 26 detected under normal
condition. In a case of the gain failure, since the
waveform detected by the abnormal current detector 26 is
- 37 -
a waveform similar to that of the waveform (a-1), it can
be said that the waveform of the differential value is a
waveform also identical with the waveform detected by the
abnormal current detector 26. By utilizing the feature,
the converter side abnormality determination device 71
determines that the current detector 26 detecting similar
waveform is abnormal by comparing the waveform of the
differential value data with the waveform detected by each
of the current detectors.
[0076]
Further, in a case where the S phase current detector
27 is abnormal (for example, gain failure is assumed in
the current detector 27), the differential values for all
of the phases contain values deviated from zero as shown
in (d-1), (d-2), and (d-3) of Fig. 4D to reveal that any
one of the current detectors is abnormal. The differential
value data for each of the phases provide similar waveforms
as shown in (d-1), (d-2), and (d-3). In the same manner
as described above, it can be said that the waveform of
the differential value is also similar to the waveform
detected by the abnormal current detector 27. By utilizing
the feature, the converter side abnormality determination
device 71 compares the waveform of the differential value
data with the waveform detected by each of the current
- 38 -
detectors to specify that the current detector 27 detecting
a similar waveform is abnormal.
[0077]
Further, in a case where the T phase current detector
28 is abnormal (for example, gain failure is assumed in
the current detector 28), the differential values for all
of the phases contain values deviated from zero as shown
in (e-1), (e-2), and (e-3) of Fig. 4E to reveal that any
one of the current detectors is abnormal. The differential
value data for each of the phases provide similar waveforms
as shown in (e-1), (e-2), and (e-3). In the same manner
as described above, it can be said that the waveform of
the differential value is also similar to the waveform
detected by the abnormal current detector 28. By utilizing
the feature, the converter side abnormality determination
device 71 compares the waveform of the differential value
data with the waveform detected by each of the current
detectors to specify that the current detector 28 detecting
a similar waveform is abnormal.
[0078]
Abnormality can be determined for any one of abnormal
current detector 34, 35, or 36 by performing the same
processing as described above also on the side of the
inverter unit 3.
- 39 -
[0079]
As has been described above, abnormal current
detector can be determined without storing the reference
data by using and comparing values obtained mutually from
the detection values of the three current detectors 26,
27, and 28 (current detectors 34, 35, and 36) (mutual
comparison).
[0080]
Then, a power conversion apparatus according to a
second embodiment is to be described.
[0081]
Fig. 5 is an entire configurational view of a power
conversion apparatus according to the second embodiment.
Configurations identical with those of the power conversion
apparatus according to the first embodiment shown in Fig.
1 carry same reference numerals.
[0082]
The power conversion apparatus 101 according to the
second embodiment is configured in the power conversion
apparatus 100 according to the first embodiment except by
using a two-level converter for the converter unit 2, using
a two-level inverter for the inverter unit 3, and detecting
the potential between the electrodes of the converter side
smoothing capacitors 22 and 23 by a DC voltage detector
- 40 -
29.
[0083]
While the generated ripple current is different
depending on the difference of the conversion system (pulse
waveform) between three-level and two-level, the converter
side abnormality determination device 71 can determine the
abnormality of the current detectors 26, 27, and 28
appropriately by performing the processing identical with
that of the first embodiment (for example, comparison with
the reference data) based on the detection values of the
current detectors 26, 27, and 28 also in the power
conversion apparatus 101. Further, the inverter side
abnormality determination device 72 can determine the
abnormality of the current detectors 34, 35, and 36
appropriately by performing the processing identical with
that of the first embodiment (for example, comparison with
the reference data) based on the detection values of the
current detectors 34, 35, and 36.
[0084]
Then, a power conversion apparatus according to a
third embodiment is to be described.
[0085]
Fig. 6 is an entire configurational view of a power
conversion apparatus according to the third embodiment.
- 41 -
Configurations identical with those of the power conversion
apparatus according to the first embodiment shown in Fig.
1 carry same reference numerals.
[0086]
A power conversion apparatus 102 according to the
third embodiment additionally has a converter side output
estimation device 74 and an inverter side output estimation
device 75 in the power conversion apparatus 100 according
to the first embodiment.
[0087]
The converter side output estimation device 74
estimates an accurate detection value (detection value to
be detected originally) for the detection target of the
abnormal current detector. The converter side output
estimation device 74 may be configured also by executing
a program stored in a memory unit by an unillustrated
processor.
[0088]
For the method of estimating an accurate detection
value for the detection target of the abnormal current
detector utilizes a relation that in a case where each of
the current detectors is normal, the total current value
obtained by adding detection values of the converter side
current detectors 26, 27, and 28 is zero in the power
- 42 -
conversion apparatus 102. Based on such a relationship,
in a case where any one of the current detectors is abnormal,
an accurate detection value for the measurement target of
the abnormal current detector can be estimated by
subtracting, from zero, a value obtained by addition of
detection values from two normal current detectors.
[0089]
Then, specific configuration and operation of the
converter side output estimation device 74 are to be
described.
[0090]
Fig. 7 is a partial configurational view including
an output estimation device of a power conversion apparatus
according to a third embodiment. In Fig. 7, IRFB_c denotes
a detection value from an R phase current detector 26,
ISFB_c denotes a detection value from an S phase current
detector 27, and ITFB_c denotes a detection value from a
T phase current detector 28. Further, Fig. 7 shows an
example where the T phase current detector 28 is abnormal.
[0091]
The converter side abnormality determination device
71 is inputted with a detection value (IRFB_c) from the
R phase current detector 26, a detection value (ISFB_c)
from an S phase current detector 27, and a T phase detection
- 43 -
value (ITFB_c) from a T phase current detector 28, and when
it is determined that one of the current detectors is
abnormal, the abnormal determination information showing
an abnormal current detector is outputted to the converter
side output estimation device 74. In the example shown in
Fig. 7, the converter side abnormality determination device
71 determines that the current detector 28 is abnormal and
outputs information that the current detector 28 is
abnormal (ITFB_c abnormality determination information)
to the converter side output estimation device 74.
[0092]
The converter side output estimation device 74 adds
a detection value from the current detector 26 (IRFB_c),
and a detection value from the current detector 27 (ISFB_c)
to calculate the total current value of the two phases
(IRS_c).
[0093]
The converter side output estimation device 74
subtracts the total current value of two phases (IRS_c)
from zero and calculate an estimated value (ITFBH_c) that
is estimated to be detected from the current detector 28,
if it is normal.
[0094]
A selection unit 74a of the converter side output
- 44 -
estimation device 74 is inputted with a detection value
from the current detector 28 (ITFB_c) and an estimated value
of the current detector 28 (ITFBH_c). In a case where the
information that the current detector 28 is abnormal
(ITFB_c abnormal determination information) is inputted
from the converter side abnormality determination device
71, the selection unit 74a selects the estimated value of
the current detector 28 (ITFBH_c), and outputs to a
predetermined transmission destination (converter control
device 5 in this example), and if the information that the
current detector 28 is abnormal (ITFB_c abnormality
determination information) is not inputted from the
converter side abnormality determination device 71, the
selection unit 74a selects the detection value from the
current detector 28 (ITFB_c) and outputs to a
predetermined transmission designation.
[0095]
With such a configuration, if the current detector
28 is abnormal, an appropriate estimation value can be
outputted instead of the detection value from the current
detector 28. Fig. 7 shows a relevant configuration in a
case where the current detector 28 is abnormal, but an
appropriate estimation value can be outputted upon
abnormality in the same configuration also in other current
- 45 -
detectors.
[0096]
For example, the current detector 26 may include a
configuration of replacing the current detector 28 with
the current detector 26 and the current detector 27 may
include a configuration of replacing the current detector
28 with the current detector 27.
[0097]
While the converter side configuration and operation
have been described, an appropriate estimation value can
be outputted in a case if any one of the current detectors
34, 35, and 36 is abnormal by the same configuration and
the operation also on the inverter side (inverter side
output estimation device 75). In the explanation
described above, the inverter side operation is attainable
by replacing the R phase into the U phase, the S phase into
the V phase and the T phase into the W phase, and by replacing
the current detectors 26, 27, and 28 with the current
detectors 34, 35, and 36. Fig. 7 shows an example of a
configuration in a case where the W phase current detector
36 is abnormal.
[0098]
As has been described above, in the power conversion
apparatus 102 according to the third embodiment, since a
- 46 -
normal detection value of the detection target is estimated
in the abnormal current detector based on the detection
value of the normal current detector other than the abnormal
current detector, the power conversion apparatus 102 can
be used without replacing the abnormal current detector.
For example, the power conversion apparatus 102 can be
operated continuously, that is, subjected to tide over
operation. Thus, there is no requirement for the unplanned
outage of the power conversion apparatus 102.
[0099]
The tide over operation due to the configuration
shown in Fig. 7 is applicable also to the power conversion
apparatus 101 according to the second embodiment shown in
Fig. 5.
[0100]
The present invention is not restricted to the
embodiments described above but can be practiced with
appropriate modifications without departing the gist of
the present invention.
[0101]
For example, in the embodiments described above, the
processing performed by the converter side abnormality
determination device 71, the converter side output
estimation device 74, the inverter side abnormality
- 47 -
determination device 72, and the inverter side output
estimation device 75 can also be performed partially or
entirely by an exclusive hardware circuit.
[0102]
Further, in any one of the embodiments described
above, the converter side abnormality determination device
71 or the inverter side abnormality determination device
72 may also be adapted to store the history of preliminary
abnormal values of the detection value from the current
detector (preliminary abnormal value is an abnormal value
not leading to abnormality determination) (for example,
execution date and preliminary abnormal value), recognize
the change of the preliminary abnormal value by the current
detector based on the history of the abnormal value, predict
a period till exceeding a predetermined threshold value
for determining the output abnormality of the current
detector, that is, the period till occurrence of the
abnormality and display the result of predict to the display
device 73. In such a configuration, the time upon
abnormality occurrence can be recognized previously,
thereby enabling to prevent occurrence of abnormality and
preparation for response upon abnormality occurrence.
[0103]
In the embodiments described above, the power
- 48 -
conversion apparatus includes the converter unit 2 and the
inverter unit 3, but the present invention is also
applicable to the power conversion apparatus having only
one of the converter unit 2 or the inverter unit 3.

We claim:
1. A power conversion apparatus having at least one
power conversion unit of a converter power conversion unit
for converting AC power into voltage at plural potentials
or an inverter power conversion unit for converting voltage
at plural potentials into AC power, the apparatus
comprising:
current detectors for detecting a current flowing
between the power conversion unit and a power supply or
a loading device; and
an abnormality determination device for determining
abnormality of the current detector based on a value of
ripple current contained in a detection value of the current
detectors.
2. The power conversion apparatus according to claim
1, further comprising a memory unit for storing a reference
value of ripple current assumed to be contained in the
detection value of the current detector,
wherein the abnormality determination device
determines the abnormality of the current detector based
on the reference value of the ripple current stored in the
memory unit and the value of the ripple current contained
in the detection value of the current detector.
- 50 -
3. The power conversion apparatus according to claim
2,
wherein the memory unit stores, as a reference value,
a non-loaded reference value that is a reference value of
the ripple current assumed to be contained in the detection
value of the current detector upon operation of the power
conversion unit under non-loaded conditions, and
the abnormality determination device determines the
abnormality of the current detector based on the value of
the ripple current contained in the detection value of the
current detector and the non-loaded reference value upon
operation of the power conversion unit under non-loading
conditions.
4. The power conversion apparatus according to any
one of claims 1 to 3, comprising a plurality of the current
detectors for detecting respective currents of plural
phases flowing between the power conversion unit and the
power supply or the loading device.
5. The power conversion apparatus according to claim
4, wherein the abnormality determination device determines
that the power conversion unit is abnormal in a case where
all of the detection values of the plural current detectors
are zero or close to zero.
6. The power conversion apparatus according to claim
- 51 -
4 or 5, wherein the abnormality determination device
determines that a wiring connected to any one of current
detectors is abnormal in a case where any one of the
detection values of the plural current detectors is zero
or close to zero.
7. The power conversion apparatus according to claim
2, wherein the abnormality determination device determines
that the current detector is abnormal when the value of
the ripple current contained in the detection value of the
current detector deviates by more than a predetermined
value from the reference value of the ripple current stored
in the memory unit.
8. The power conversion apparatus according to claim
2,
wherein the reference value of the ripple current
stored in the memory unit is a reference value calculated
based on the detection values of the current detector upon
installation and operation of the power conversion
apparatus, and
the abnormality determination device determines that
the current detector is abnormal in a case where the value
of the ripple current contained in the detection value of
the current detector deviates by more than a predetermined
value from the reference value of the ripple current stored
- 52 -
in the memory unit.
9. The power conversion apparatus according to claim
2, wherein the abnormality determination device determines
the abnormality in a case where an amended current value
obtained by multiplying the value of the ripple current
contained in the detection value by a coefficient in
consideration of a fluctuation of a DC voltage by the power
conversion unit deviates by more than a predetermined value
from the reference value stored in the memory unit.
10. The power conversion apparatus according to claim
4, having a plurality of the current detectors for detecting
respective currents of three phases flowing between the
power conversion unit and the power supply or the loading
device, further comprising an output estimation device for
estimating a value of a current as a detection target of
the current detector determined as abnormal based on the
detection values of the current detectors of two phases
other than the phase as the detection target of the current
detector determined as abnormal.
11. The power conversion apparatus according to claim
1, having a plurality of the current detectors for detecting
respective currents of three phases flowing between the
power conversion unit and the power supply or the loading
device,
- 53 -
wherein the abnormality determination device
determines an abnormal current detector among the plurality
of current detectors based on the differential value
between a value of the ripple current contained in the
current value of a certain phase calculated from the value
of the ripple current contained in the current value of
other two phases and a value of the ripple current contained
in the detection value of the certain phase, and the value
of the ripple current contained in the detection value of
each of phases.
12. The power conversion apparatus according to claim
11 further comprising an output estimation device for
estimating a value of a current as a detection target of
the current detector which has been determined as abnormal
based on the detection values of the current detectors of
two phases other than the phase as the detection target
of the current detector determined as abnormal.
13. The power conversion apparatus according to any
one of claims 1 to 12, wherein the abnormality determination
device displays information for abnormality on a display
device upon determination of the occurrence of abnormality.
14. The power conversion apparatus according to claim
13, wherein the abnormality determination device stores
a history of the detection value by the current detector,
- 54 -
predicts the period till generation of the abnormality in
the current detector based on the history of the detection
value, and displays the result of the prediction on the
display device.
15. An abnormality detection method by a power
conversion apparatus having at least one power conversion
unit of a converter power conversion unit for converting
AC power to DC power at plural potentials and an inverter
power conversion unit for converting voltage at plural
potentials into AC power, the method comprising:
detecting a current flowing between the power
conversion unit and a power supply or a loading device by
a current detector; and
determining the abnormality of the current detector
based on the value of the ripple current contained in the
detection value of the current detector.