2. The power convertor according to claim 1, wherein the abnormality determiner includes a storage unit that stores a detection value of a reference value of the DC voltage detector during charging of the smoothing capacitor, and wherein the abnormality determiner determines an abnormality of the DC voltage detector based on the reference value stored in the storage unit and the detection value.

3. The power convertor according to claim 2, wherein the abnormality determiner stores the detection value of the DC voltage detector in the storage unit as the reference value during charging of the smoothing capacitor at a predetermined time point.

4. The power convertor according to claim 2 or 3, wherein the abnormality determiner stores the reference value of the detection values of the DC voltage detector in the storage unit at a plurality of time points during the charging.

5. The power convertor according to any one of claims 2 to 4, wherein the abnormality determiner acquires voltage information indicating a charging voltage during the charging, calculates a correction reference value that is obtained by correcting the reference value based on the voltage information, and determines an abnormality of the DC voltage detector based on the correction reference value.

6. The power convertor according to any one of claims 1 to 5, wherein the smoothing capacitor includes a convertor-side smoothing capacitor that is connected between two potentials of a plurality of potentials on the convertor side and an inverter-side smoothing capacitor that is connected between two potentials of a plurality of potentials on the inverter side, wherein the DC voltage detector includes a convertor-side DC voltage detector that detects a potential difference between potentials to which the convertor-side smoothing capacitor is connected and an inverter-side DC voltage detector that detects a potential difference between potentials to which the inverter-side smoothing capacitor is connected, and wherein the abnormality determiner determines an abnormality of the convertor-side DC voltage detector and the inverter-side DC voltage detector based on a detection value obtained by the convertor-side DC voltage detector and a detection value obtained by the inverter-side DC voltage detector when the convertor-side smoothing capacitor and the inverter-side smoothing capacitor are charged.

7. The power convertor according to any one of claims 1 to 5, wherein the convertor converts the AC power into a first potential, a second potential that is lower than the first potential, and a third potential that is lower than the second potential, wherein the inverter converts the first potential, the second potential, and the third potential of DC power into an AC power, and includes a first smoothing capacitor that is connected between the first potential and the second potential, a second smoothing capacitor that is connected between the second potential and the third potential, a first DC voltage detector that detects a potential difference between potentials to which the first smoothing capacitor is connected, and a second DC voltage detector that detects a potential difference between potentials to which the second smoothing capacitor is connected, and wherein the abnormality determiner determines an abnormality of the first DC voltage detector and the second DC voltage detector based on detection values by the first DC voltage detector and the second DC voltage detector when the first smoothing capacitor and the second smoothing capacitor are charged.

8. The power convertor according to claim 7, wherein in a case where a voltage value obtained by the first DC voltage detector and the second DC voltage detector is zero or a value close to zero at a plurality of the time points during the charging, the abnormality determiner determines that a charging circuit is abnormal.

9. The power convertor according to claim 7, wherein in a case where a voltage value obtained by one of the first DC voltage detector and the second DC voltage detector is zero or a value close to zero at a plurality of the time points during the charging, the abnormality determiner determines that wiring connected to the DC voltage detector is abnormal.

10. The power convertor according to any one of claims 7 to 9, further comprising: a resistor that is connected between a second potential on the inverter side and a second potential on the convertor side, wherein the first smoothing capacitor includes a first convertor-side smoothing capacitor that is connected between the first potential and the second potential on the convertor side, and a first inverter-side smoothing capacitor that is connected between the first potential and the second potential on the inverter side, wherein the second smoothing capacitor includes a second convertor-side smoothing capacitor that is connected between the second potential and the third potential on the convertor side, and a second inverter-side smoothing capacitor that is connected between the second potential and the third potential on the inverter side, wherein the first DC voltage detector includes a first convertor-side DC voltage detector that detects a potential difference between potentials to which the first convertor-side smoothing capacitor is connected and a first inverter-side DC voltage detector that detects a potential difference between potentials to which the first inverter-side smoothing capacitor is connected, wherein the second DC voltage detector includes a second convertor-side DC voltage detector that detects a potential difference between potentials to which the second convertor-side smoothing capacitor is connected and a second inverter-side DC voltage detector that detects a potential difference between potentials to which the second inverter-side smoothing capacitor is connected, and wherein the abnormality determiner determines abnormality of the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector based on detection values obtained by the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector when the first convertor-side smoothing capacitor, the second convertor-side smoothing capacitor, the first inverter-side smoothing capacitor, and the second inverter-side smoothing capacitor are charged.

11. The power convertor according to claim 10, wherein the abnormality determiner compares the detection values obtained by the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector with each other to specify a DC voltage detector having an abnormality in the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, or the second inverter-side DC voltage detector.

12. The power convertor according to claim 10 or 11, further comprising: an output estimation unit that estimates a detection value of a detection target of the DC voltage detector in which the abnormality is generated based on the detection values obtained by the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector.

13. The power convertor according to any one of claims 1 to 12, wherein in a case where it is determined that the abnormality is generated, the abnormality determiner displays information related to the abnormality on a display device.

14. The power convertor according to claim 13, wherein the abnormality determiner stores an history of the detection value obtained by the DC voltage detector during a plurality of times of charging, predicts a period until the abnormality of the DC voltage detector is generated based on the history of the detection value, and displays a prediction result on the display device.

15. A abnormality detection method in a power convertor including a convertor that converts an AC power into a plurality of potentials of DC power, an inverter that converts a plurality of potentials into an AC power, a smoothing capacitor that is connected between two potentials of a plurality of potentials and suppresses a potential fluctuation between the potentials, and a DC voltage detector that detects a potential difference between potentials to which the smoothing capacitor is connected, the method comprising: acquiring a detection value obtained by the DC voltage detector during charging of the smoothing capacitor; and determining an abnormality of the DC voltage detector based on the acquired detection value.

The present invention relates to a power convertor including a convertor and an inverter, and an abnormality detection method for detecting an abnormality in a power convertor, and more particularly to a technique for detecting an abnormality of a DC voltage detector in a power convertor. BACKGROUND ART
A power convertor that converts power of an AC power supply to power of a variable voltage variable frequency is known. The power convertor includes a smoothing capacitor and a DC voltage detector that measures a both-end voltage of the smoothing capacitor in a DC circuit, and controls an output DC voltage to be constant.
For example, as a technique for confirming normality of the smoothing capacitor, a technique that determines an abnormality from a behavior of a charging voltage during initial charging is known (for example, see JP-A-2005-354789) . In addition, in a power convertor that converts power of an AC power supply into power of a variable voltage variable frequency, one that includes a plurality of DC voltage detectors is known (for example, see JP-A-2008-011606).
In JP-A-2005-354789, in order to confirm the normality

of the smoothing capacitor, a technique for determining the abnormality from the behavior of the DC voltage during initial charging is disclosed. However, a technique for determining an abnormality of the DC voltage detector in the power convertor is not disclosed. The DC voltage detector is essential for controlling the DC voltage of the power convertor and the abnormality of the DC voltage detector causes instability of an operation of a system and in the worst case brings about an unplanned stop of the system resulting in serious damage.
SUMMARY OF THE INVENTION
The present invention is made in view of the above circumstances and an object of the invention is to provide a technique capable of appropriately detecting an abnormality of a DC voltage detector in a power convertor.
According to an aspect of the present invention, there is provided the power convertor that includes a convertor that converts an AC power into a plurality of potentials of DC power, and an inverter that converts a plurality of potentials into an AC power, the power convertor including: a smoothing capacitor that is connected between two potentials of a plurality of potentials and suppresses a potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between potentials to which the smoothing capacitor is connected; and an abnormality determiner that

determines an abnormality of the DC voltage detector based on a detection value obtained by the DC voltage detector during charging of the smoothing capacitor.
According to the invention, an abnormality of the DC voltage detector in the power convertor can be appropriately detected.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram of an entire configuration of a power convertor according to a first embodiment.
Fig. 2 is a graph for explaining a DC voltage value detected by a DC voltage detector during charging in the first embodiment.
Fig. 3 is a flowchart of an abnormality determining process by an abnormality determiner according to the first embodiment.
Fig. 4 is a diagram of an entire configuration of a power convertor according to a second embodiment.
Fig. 5 is a diagram of an entire configuration of a power convertor according to a third embodiment.
Fig. 6 is a diagram of an entire configuration of a power convertor according to a fourth embodiment.
Fig. 7 is a diagram of an entire configuration of a power convertor according to a fifth embodiment.
Fig. 8 is a diagram of a part of a configuration including

an output estimator of the power convertor according to the fifth embodiment.
Fig. 9 is a diagram of an entire configuration of a power convertor according to a sixth embodiment.
DETAILED DESCRIPTION OF THE INVENTION
Several embodiments will be described with reference to the drawings. The embodiments described below do not limit the invention according to the claims and all the elements and combinations thereof described in the embodiment are not essential to the solving means of the invention.
First, a power convertor according to a first embodiment will be described.
Fig. 1 is a diagram of an entire configuration of the power convertor according to the first embodiment.
A power convertor 100 includes an AC power supply 1, a convertor unit (also referred to as a convertor) 2 that converts an AC power from the AC power supply 1 into DC power, an inverter unit (also referred to as an inverter) 3 that converts the DC power output by the convertor unit 2 into a desired AC power, an electric motor 4 that is driven by the AC power output by the inverter unit 3, a convertor control device 5 that controls the convertor unit 2, and an inverter control device 6 that controls the inverter unit 3.
The convertor unit 2 is a so-called three-level convertor

and converts the AC power into the DC power of 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 the DC power of a positive potential (first potential) level, a neutral point (zero) potential (second potential) level, and a negative potential
(third potential) level into the AC power for the electric motor 4. The positive potential levels of the convertor unit 2 and the inverter unit 3 are connected by a P wiring 40, the neutral point potential levels are connected by a C wiring 41, and the negative potential levels are connected by an N wiring 42. The convertor unit 2 includes a convertor power conversion unit 21, a convertor P-side smoothing capacitor 22
(first convertor-side smoothing capacitor, first smoothing convertor, and convertor-side smoothing capacitor: may be referred to as a smoothing capacitor 22) for suppressing fluctuation of the DC voltage, a convertor N-side smoothing capacitor 23 (second convertor-side smoothing capacitor, second smoothing convertor, and convertor-side smoothing capacitor: may be referred to as a smoothing capacitor 23), a convertor P-side DC voltage detector 25 (first convertor-side DC voltage detector: may be referred to as a DC voltage detector 25) for measuring an inter-terminal voltage of the convertor P-side smoothing capacitor 22, a

convertor N-side DC voltage detector 26 (second convertor-side DC voltage detector: may be referred to as a DC voltage detector 26) for measuring an inter-terminal voltage of the convertor N-side smoothing capacitor 23, and a convertor neutral point resistor 24 that is connected to the C wiring 41 and suppresses DC resonance.
The inverter unit 3 includes a inverter power conversion unit 31, an inverter P-side smoothing capacitor 32 (first inverter-side smoothing capacitor, first smoothing convertor, and inverter-side smoothing capacitor: may be referred to as a smoothing capacitor 32), an inverter N-side smoothing capacitor 33 (second inverter-side smoothing capacitor, second smoothing convertor, and inverter-side smoothing capacitor: may be referred to as a smoothing capacitor 33), an inverter P-side DC voltage detector 35 (first inverter-side DC voltage detector: may be referred to as a DC voltage detector 35) for measuring an inter-terminal voltage of the inverter P-side smoothing capacitor 32, an inverter N-side DC voltage detector 36 (second inverter-side DC voltage detector: may be referred to as a DC voltage detector 36) for measuring an inter-terminal voltage of the inverter N-side smoothing capacitor 33, and an inverter neutral point resistor 34 that is connected to the C wiring 41 and suppresses DC resonance.
The convertor control device 5 controls the convertor power conversion unit 21 so that the converted DC power has

a desired value. The inverter control device 6 controls the inverter power conversion unit 31 so that an output torque and a speed of the electric motor 4 satisfy desired characteristics.
The power convertor 100 further includes a current detector 7 that detects an output current of the convertor unit
2 and outputs the output current, a speed detector 8 that is directly connected to the electric motor 4, detects a speed of the electric motor 4, and outputs the speed, and a current detector 9 that detects an output current of the inverter unit
3 and outputs the output current.
Signals (output signals) of the detection values detected by the current detector 7 and the DC voltage detectors 25 and 2 6 are input into the convertor control device 5. The convertor control device 5 performs various calculating processes based on the input detection value and outputs a signal for controlling the convertor power conversion unit 21.
Signals (output signals) of the detection values detected by the speed detector 8, the current detector 9, and the DC voltage detectors 35 and 36 are input into the inverter control device 6. The inverter control device 6 performs various calculating processes based on the input detection value and outputs a signal for controlling the inverter power conversion unit 31.
The convertor control device 5 includes a DC voltage

command generator 51, a DC voltage controller 52, a current controller 53, a pulse generator 54, a neutral point voltage controller 55, and a charging controller 56.
The DC voltage command generator 51 outputs a DC voltage command value indicating a voltage value of the DC voltage output from the convertor unit 2 to the DC voltage controller 52.
The DC voltage controller 52 calculates a convertor output current command value based on the DC voltage command value input from the DC voltage command generator 51 and the detection values of the DC voltage input from the DC voltage detectors 25 and 26, and outputs the convertor output current command value to the current controller 53. Specifically, the DC voltage controller 52 calculates the convertor output current command value so that a total value of the detection value of the DC voltage input from each of the DC voltage detectors 25 and 2 6 coincides with the DC voltage command value .
The neutral point voltage controller 55 calculates a voltage command so that the neutral point voltage becomes zero based on a difference between the detection values of the DC voltage input from each of the DC voltage detectors 25 and 26, and outputs the voltage command to the current controller 53.
The current controller 53 calculates a convertor voltage command value so that the convertor output current detection value output from the current detector 7 coincides with the

convertor output current command value, which is input from the DC voltage controller 52, and outputs the convertor voltage command value to the pulse generator 54. In this case, the current controller 53 calculates the convertor voltage command value in consideration of the voltage command input from the neutral point voltage controller 55.
The pulse generator 54 calculates a pulse signal for ON and OFF control of each switching element of the convertor power conversion unit 21 so that the output voltage by the convertor power conversion unit 21 coincides with the convertor output voltage command value input from the current controller 53, and outputs the pulse signal to the convertor power conversion unit 21.
The charging controller 56 performs control for charging (initial charging) the convertor P-side smoothing capacitor 22, the convertor N-side smoothing capacitor 23, the inverter P-side smoothing capacitor 32, and the inverter N-side smoothing capacitor 33 before starting operations of the convertor unit 2 and the inverter unit 3. Specifically, when initial charging is performed, the charging controller 56 notifies a charging circuit 71 and an abnormality determiner 72, which are described later, of the initial charging.
The inverter control device 6 includes a speed command generator 61, a speed controller 62, a current controller 63, a pulse generator 64, and a neutral point voltage controller

65.
The speed command generator 61 outputs a speed command value indicating a speed for operating the electric motor 4 to the speed controller 62.
The speed controller 62 calculates an inverter output current command value so that a speed detection value which is input from the speed detector 8 coincides with the speed command value which is input from the speed command generator 61, and outputs the inverter output current command value to the current controller 63.
The neutral point voltage controller 65 calculates a voltage command so that the neutral point voltage becomes zero based on a difference between the detection values of the DC voltage input from each of the DC voltage detectors 35 and 36, and outputs the voltage command to the current controller 63.
The current controller 63 calculates an inverter voltage command value so that an inverter output current detection value which is input from the current detector 9 coincides with the inverter output current command value which is input from the speed controller 62, and outputs the inverter voltage command value to the pulse generator 64. In this case, the current controller 63 calculates the inverter voltage command value in consideration of the voltage command which is input from the neutral point voltage controller 65.
The pulse generator 64 calculates a pulse signal for ON
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and OFF control of each switching element of the inverter power conversion unit 31 so that the output voltage by the inverter power conversion unit 31 coincides with an inverter output voltage command value which is input from the current controller 63, and outputs the pulse signal to the inverter power conversion unit 31.
Next, a configuration related to abnormality determination in the power convertor 100 will be described.
The power convertor 100 includes a charging power supply 70, the charging circuit 71, the abnormality determiner 72, and a displayer 73.
The charging power supply 70 is a power supply that charges the smoothing capacitors 22, 23, 32, and 33. The charging power supply 70 is, for example, an AC power supply.
The charging circuit 71 is a circuit for charging the smoothing capacitors 22, 23, 32, and 33 by power which is input from the charging power supply 70. The charging circuit 71 includes, for example, a configuration of a contactor for opening and closing a wiring to the charging power supply 70, a diode for rectifying the alternating current, a fuse for circuit protection, or the like. In the embodiment, in a case where the charging circuit 71 receives a start instruction of the initial charging from the charging controller 56, the wiring between the charging circuit 71 and the charging power supply 70 is in a closed state.
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The displayer 73 is, for example, a display device capable of displaying information of a liquid crystal display or the like, and displays various pieces of information.
The abnormality determiner 72 compares the DC voltage value (detection value) which is input from the DC voltage detectors 25, 26, 35, and 36, with data (DC voltage data: reference data) related to a temporal change (behavior) of the DC voltage value during the initial charging, which is stored in a memory 72a (storage unit), and determines whether or not there is an abnormality in the DC voltage detectors 25, 26, 35, and 36. In a case where a difference between the detection value and a value (reference value) of the reference data at the time point corresponding to at the time of detection of the detection value exceeds a predetermined threshold, the abnormality determiner 72 determines that, for example, the DC voltage detector, which detects the detection value, is abnormal. Here, the reference data related to the behavior of the DC voltage detected during the initial charging can be calculated based on charging power, a capacity of the smoothing capacitor, a constant which is determined by the configuration of the charging circuit 71. Therefore, the reference data may be calculated in advance by calculation and the calculated reference data may be stored in the memory 72a.
In a case where the abnormal DC voltage detector is detected, the abnormality determiner 72 displays information
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(for example, information (for example, the number of a device) capable of specifying the abnormal DC voltage detector) related to the abnormality, and a message for recommending inspection, exchange, or the like in displayer 73. Moreover, the abnormality determiner 72 may be configured by a processor (not illustrated) executing a program stored in the memory.
Next, the abnormality determination by the abnormality determiner 72 according to the first embodiment will be described specifically.
Fig. 2 is a graph for explaining the DC voltage value detected by the DC voltage detector during charging in the first embodiment.
The DC voltage value (detection value) detected from each of the DC voltage detectors 25, 26, 35, and 36, and the reference data for determining the abnormality of the DC voltage detector are illustrated in Fig. 2. Moreover, an example of a case where the DC voltage detector 26 is abnormal is illustrated in Fig. 2.
The reference data is a DC voltage value from a charging start time T0, which is obtained by calculation in advance by using the charging power supply 70, the charging circuit 71, and the capacity of the smoothing capacitors 22, 23, 32, and 33. The reference data is stored in advance in the memory 72a. In the embodiment, a sequential DC voltage value from the charging start time may be used as the reference data, or a
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DC voltage value of a plurality of points (8 points from T1 to T8 in Fig. 2) every predetermined time from the charging start time may be used as the reference data.
In a case where there is no abnormality in the DC voltage detector, the detection value of the DC voltage detector is equal to or close to the reference data, but in a case where there is an abnormality, as illustrated in an output of the DC voltage detector 26 of Fig. 2, a large deviation from the reference data occurs.
Therefore, the abnormality determiner 72 compares the detection value of the four DC voltage detectors 25, 26, 35, and 36 from the initial charging start with the DC voltage value (reference value) of the reference data at the time point, and determines whether or not the difference is within a predetermined threshold. In a case where the difference between the detection value and the reference value exceeds the predetermined threshold, it is determined that the DC voltage detector which detects the detection value is abnormal and messages for the abnormality of the DC voltage detector and for recommending inspection and exchange of the DC voltage detector are displayed in the displayer 73.
Here, even in a case where the detection value of the DC voltage detector is out of the reference value, it may not necessarily be the abnormality of the DC voltage detector. Therefore, in order to reduce a risk of erroneous determination
15

that the DC voltage detector is abnormal due to a factor except the abnormality of the DC voltage detector, the abnormality determiner 72 according to the embodiment performs an abnormality determining process indicated as follows.
Fig. 3 is a flowchart of the abnormality determining process by the abnormality determiner according to the first embodiment.
The abnormality determiner 72 determines whether or not all the detection values of the four DC voltage detectors 25, 26, 35, and 36 are zero (or a value close to zero) (step S11). Moreover, in the embodiment, the abnormality determiner 72 determines whether or not all the detection values of the four DC voltage detectors 25, 26, 35, and 36 are zero at all a plurality of the time points (for example, eight time points T1 to T8 illustrated in Fig. 2).
As a result, in a case where all the detection values of the DC voltage detectors 25, 26, 35, and 36 are zero (step S11: Yes), for example, there is a possibility that an abnormality such as disconnection occurs in the charging circuit 71. Therefore, the abnormality determiner 72 determines that the charging circuit 71 is abnormal and displays information (“charging circuit abnormality”) indicating that the abnormality occurs in the charging circuit on the displayer 73 (step S12), and the process proceeds to step S19.
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On the other hand, in a case where all the detection values of the DC voltage detectors 25, 26, 35, and 36 are not zero (step S11: No), the abnormality determiner 72 determines whether or not the detection value of any one of the DC voltage detectors 25, 26, 35, and 36 is zero (step S13).
As a result, in a case where the detection value of any one of the DC voltage detectors 25, 26, 35, and 36 is zero (step S13: Yes), an abnormality is considered due to disconnection, looseness, or the like of a loop (DC voltage detection loop: wiring) for performing the DC voltage detection used by the DC voltage detector of which the detection value is zero. Therefore, the abnormality determiner 72 determines that the abnormality occurs in the DC voltage detection loop and displays information (“DC voltage detection loop abnormality”) indicating that the abnormality occurs in the DC voltage detection loop on the displayer 73 (step S14), and the process proceeds to step S19.
On the other hand, in a case where the detection value of any one of the DC voltage detectors 25, 26, 35, and 36 is not zero (step S13: No), the abnormality determiner 72 determines whether or not the charging power supply 70 is abnormal from a fluctuation amount of a voltage of the charging power supply 70 and the detection values of the DC voltage detectors 25, 26, 35, and 36 (step S15). Moreover, the fluctuation amount of the voltage of the charging power supply
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70 may be acquired from, for example, a higher-level device that supplies the charging power supply 70, or may be acquired from a sensor which is provided in the power convertor 100 to measure the fluctuation amount of the voltage of the charging power supply 70.
As a result, in a case where the charging power supply 70 is abnormal (step S15: Yes), the abnormality determiner 72 determines that the charging power supply is abnormal and displays information (“charging power supply abnormality”) indicating that the charging power supply is abnormal on the displayer 73 (step S16), and the process proceeds to step S19.
On the other hand, in a case where the charging power supply 70 is not abnormal (step S15: No), the abnormality determiner 72 compares the reference value with the detection value of each of the DC voltage detectors 25, 26, 35, and 36, and determines whether or not there is a deviation larger than a predetermined threshold between the reference value and the detection value (step S17). Moreover, in the embodiment, the abnormality determiner 72 determines a deviation between the detection values of the four DC voltage detectors 25, 26, 35, and 36, and the reference value at all the plurality of the time points (for example, eight time points T1 to T8 illustrated in Fig. 2).
As a result, in a case where a deviation larger than the predetermined threshold between the reference value and the
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detection value is present (step S17: Yes), the abnormality determiner 72 determines that the DC voltage detector which outputs the detection value in which the deviation larger than the predetermined threshold is present is abnormal and displays information (“DC voltage detector abnormality”) indicating that the DC voltage detector is abnormal on the displayer 73 (step S18), and the process proceeds to step S19.
In step S19, the abnormality determiner 72 displays a sentence “please inspect and exchange abnormal portion” on the displayer 73 and the process is completed.
On the other hand, in a case where there is a deviation less than or equal to the predetermined threshold between the reference value and the detection value (step S17: No), it means that there is no abnormality in each of the DC voltage detectors 25, 26, 35, and 36 and thereby the abnormality determiner 72 completes the abnormality determining process.
As described above, in the power convertor 100 according to the first embodiment, the abnormality of the DC voltage detector is determined from the behavior of the output (detection value) of the DC voltage detector during the initial charging which is normally performed, and the display for recommending inspection and exchange of the abnormal DC voltage detector is performed. Therefore, it is possible to direct inspection and exchange of the DC voltage detector before the operation, and it is possible to prevent in advance
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unplanned stop of the system due to the abnormality of the DC voltage detector.
In the first embodiment described above, for example, in a case of using data calculated in advance as the reference data, conditions assumed at the time of calculation in advance and conditions at the actual place in which the power convertor 100 is disposed may be different. In this case, if the reference data calculated in advance is used, there is a risk that an abnormality determination of the DC voltage detector is incorrect due to an error of the reference data.
On the other hand, for example, at a time point when the DC voltage detection value of the power convertor 100 is normal (for example, at the time of installation of the power convertor 100), data of the behavior (temporal change (for example, values of a plurality of the time points)) of the detection value obtained by the DC voltage detector during the initial charging is acquired and is stored in the memory 72a, and the data may be used as the reference data. Therefore, the reference data can be data that is adapted to the actual state of the power convertor 100 and a risk of erroneous determination can be reduced.
In addition, in the first embodiment described above, for example, the outputs of the DC voltage detectors 25, 26, 35, and 36 are influenced by the fluctuation of the voltage of the charging power supply 70. Therefore, there is a risk
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that the abnormality of the DC voltage detector is erroneously determined by the fluctuation of the voltage of the charging power supply 70.
On the other hand, for example, the fluctuation amount of the voltage of the charging power supply 70 during charging is input into the abnormality determiner 72, the abnormality determiner 72 corrects the value of the reference data with a coefficient corresponding to the input fluctuation amount (for example, the coefficient is multiplied by the coefficient), the corrected value (corrected reference value) is used, and the abnormality of the DC voltage detector may be determined. Therefore, the risk of erroneous determination due to the fluctuation amount of the voltage of the charging power supply 70 during charging can be reduced.
In addition, in the first embodiment described above, the abnormality of the DC voltage detectors 25, 26, 35, and 36 is determined by comparing the reference data with the detection values of the DC voltage detectors 25, 26, 35, and 36. However, for example, the abnormality of the four DC voltage detectors 25, 26, 35, and 36 may be detected by comparing the detection values of the DC voltage detectors 25, 26, 35, and 36 with each other.
This is used that the behaviors of the detection values of the DC voltage detectors 25, 26, 35, and 36 are normal and basically coincides with each other even if there is the
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fluctuation of the voltage of the charging power supply 70. In a case where a behavior of a detection value of a certain DC voltage detector is different from behaviors of detection values of many other DC voltage detectors, it is possible to determine that the DC voltage detector which outputs the detection value with a different behavior is abnormal.
Specifically, the abnormality determiner 72 calculates a difference (or ratio) of the detection values by two DC voltage detectors for all combinations (six types in a case where the DC voltage detectors are four) of the two DC voltage detectors in all the DC voltage detectors 25, 26, 35, and 36. In a case where there are a plurality of combinations in which the difference (or ratio) of the detection values exceeds a predetermined range, it is determined that the DC voltage detector common to the plurality of the combinations is abnormal. Therefore, it is possible to specify an abnormal DC voltage detector without storing the reference data and even if there is a fluctuation of the voltage of the charging power supply 70 during charging, the fluctuation is not affected.
Next, a power convertor according to a second embodiment will be described.
Fig. 4 is a diagram of an entire configuration of the power convertor according to the second embodiment. The same reference numerals are given to the same configurations as those of the power convertor according to the first embodiment
22

illustrated in Fig. 1.
In a power convertor 101 according to the second embodiment, the convertor neutral point resistor 24 and the inverter neutral point resistor 34 are removed in the power convertor 100 according to the first embodiment, a potential between electrodes of a convertor-side smoothing capacitor 22 and an inverter-side smoothing capacitor 32 is detected by a common DC voltage detector 43, and a potential between electrodes of a convertor-side smoothing capacitor 23 and an inverter-side smoothing capacitor 33 is detected by a common DC voltage detector 44.
Also in the power convertor 101, an abnormality determiner 72 performs the same process (for example, comparison with the reference data) as that of the first embodiment based on the detection values by the DC voltage detector 43 and the DC voltage detector 44 during charging. Therefore, it is possible to appropriately determine the abnormality of the DC voltage detectors 43 and 44.
Next, a power convertor according to a third embodiment will be described.
Fig. 5 is a diagram of an entire configuration of the power convertor according to the third embodiment. The same reference numerals are given to the same configurations as those of the power convertor according to the first embodiment illustrated in Fig. 1.
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In a power convertor 102 according to the third embodiment, an inverter unit 3 is a two-level inverter and a converter unit 2 is a two-level convertor in the power convertor 100 according to the first embodiment, a potential between electrodes of convertor-side smoothing capacitors 22 and 23 is detected by a DC voltage detector 27, and a potential between electrodes of inverter-side smoothing capacitors 32 and 33 is detected by a DC voltage detector 37.
Also in the power convertor 102, an abnormality determiner 72 performs the same process (for example, comparison with the reference data) as that of the first embodiment based on the detection values by the DC voltage detector 27 and the DC voltage detector 37 during charging. Therefore, it is possible to appropriately determine the abnormality of the DC voltage detectors 27 and 37.
Next, a power convertor according to a fourth embodiment will be described.
Fig. 6 is a diagram of an entire configuration of the power convertor according to the fourth embodiment. The same reference numerals are given to the same configurations as those of the power convertor according to the third embodiment illustrated in Fig. 5.
In a power convertor 103 according to the fourth embodiment, a potential between electrodes of convertor-side smoothing capacitors 22 and 23, and a potential between
24

electrodes of inverter-side smoothing capacitors 32 and 33 are detected by a common DC voltage detector 27 in the power convertor 102 according to the third embodiment.
Also in the power convertor 103, an abnormality determiner 72 performs the same process (for example, comparison with the reference data) as that of the first embodiment based on the detection values by the DC voltage detector 27 during charging. Therefore, it is possible to appropriately determine the abnormality of the DC voltage detector 27.
Next, a power convertor according to a fifth embodiment will be described.
Fig. 7 is a diagram of an entire configuration of the power convertor according to the fifth embodiment. The same reference numerals are given to the same configurations as those of the power convertor according to the first embodiment illustrated in Fig. 1.
A power convertor 104 according to the fifth embodiment includes a new output estimator 74 in the power convertor 100 according to the first embodiment.
The output estimator 74 estimates an accurate detection value (detection value to be originally detected) for a detection target of an abnormal DC voltage detector based on detection values of a plurality of DC voltage detectors 25, 26, 35, and 36. Moreover, the output estimator 74 may be
25

configured such that a processor (not illustrated) executes a program stored in a memory.
Here, if each DC voltage detector is in a normal state in the power convertor 104, a method for estimating the accurate detection value for the detection target of the abnormal DC voltage detector is performed by using a relationship in which a combined DC voltage value obtained by adding detection values of convertor-side DC voltage detectors 25 and 26 coincides with a combined DC voltage value obtained by adding detection values of inverter-side DC voltage detectors 35 and 36. In a case where any one of the DC voltage detectors is abnormal by such a relationship, it is possible to estimate the accurate detection value of the detection target of the abnormal DC voltage detector by subtracting a detection value of one good DC voltage detector on one side from a combined DC voltage value obtained by adding detection values of two DC voltage detectors on a good side (convertor side or inverter side).
Next, a specific configuration and operation of the output estimator 74 will be described.
Fig. 8 is a diagram of a part of a configuration including the output estimator of the power convertor according to the fifth embodiment. In Fig. 8, the detection value of the DC voltage detector 25 is EPFB_c, the detection value of the DC voltage detector 26 is ENFB_c, the detection value of the DC voltage detector 35 is EPFB_i, and the detection value of the
26

DC voltage detector 36 is ENFB_i. In addition, Fig. 8 illustrates an example of a case where the DC voltage detector 26 is abnormal.
The detection value (EPFB_c) of the DC voltage detector
25, the detection value (ENFB_c) of the DC voltage detector
26, the detection value (EPFB_i) of the DC voltage detector 35, and the detection value (ENFB_i) of the DC voltage detector 36 are input into the abnormality determiner 72, and when it is determined that any one of the DC voltage detectors is abnormal, abnormality determination information indicating the abnormal DC voltage detector is output to the output estimator 74. In Fig. 8, the abnormality determiner 72 determines that the DC voltage detector 26 is abnormal and outputs information (ENFB_c abnormality determination information) that the DC voltage detector 26 is abnormal to the output estimator 74.
The output estimator 74 calculates a combined DC voltage value (VDC_c) on the convertor side by adding the detection value (EPFB_c) of the DC voltage detector 25 and the detection value (ENFB_c) of the DC voltage detector 26. In addition, the output estimator 74 calculates a combined DC voltage value (VDC_i) on the inverter side by adding the detection value (EPFB_i) of the DC voltage detector 35 and the detection value (ENFB_i) of the DC voltage detector 36.
The output estimator 74 calculates an estimated value
27

(EPFBH_c), which is estimated to be detected by the DC voltage detector 26 if it is normal, by subtracting the detection value (EPFB_c) of the DC voltage detector 25 from the combined DC voltage value (VDC_i) on the inverter side.
A selection unit 74a inputs the detection value (ENFB_c) of the DC voltage detector 26 and the estimated value (ENFBH_c) of the DC voltage detector 26 as input. In a case where information (ENFB_c abnormality determination information) that the DC voltage detector 26 is abnormal is input from the abnormality determiner 72, a selection unit 74a of the output estimator 74 selects the estimated value (ENFBH_c) of the DC voltage detector 26 and outputs the estimated value (ENFBH_c) to a predetermined transmission destination (in the example, a convertor control device 5). In a case where information (ENFB_c abnormality determination information) that the DC voltage detector 26 is abnormal is not input from the abnormality determiner 72, the selection unit 74a selects the detection value (ENFB_c) of the DC voltage detector 26 and outputs the detection value (ENFB_c) to the predetermined transmission destination.
In a case where the DC voltage detector 26 is abnormal, it is possible to output an appropriate estimated value obtained by changing the detection value of the DC voltage detector 26 by such a configuration. In Fig. 8, in a case where the DC voltage detector 26 is abnormal, related configurations
28

are illustrated. However, in a case where there is an abnormality, it is possible to output an appropriate estimated value obtained by the same configuration even in another DC voltage detector.
For example, with regard to the DC voltage detector 25, the DC voltage detector 26 may be replaced with the DC voltage detector 25. In addition, in a case of the DC voltage detector 35 or the DC voltage detector 36, the estimated value of the DC voltage detector is calculated by subtracting the detection value of the DC voltage detector from the combined DC voltage value (VDC_c) on the convertor side, and the estimated value is input into the selection unit 74a, a value selected by the selection unit 74a may be output to the inverter control device 6.
As described above, in the power convertor 104 according to the fifth embodiment, in a case where it is determined that the DC voltage detector is abnormal, a normal detection value of the detection target in the abnormal DC voltage detector is estimated based on the detection value of the good DC voltage detector other than the abnormal DC voltage detector. Therefore, it is possible to use the power convertor 104 without exchanging the abnormal DC voltage detector and, for example, it is possible to perform a temporal operation in which the power convertor is continuously operated until the next regular inspection. Therefore, there is no need to unplanned
29

stop the power convertor 104.
Next, a power convertor according to a sixth embodiment will be described.
Fig. 9 is a diagram of an entire configuration of a power convertor according to a sixth embodiment. The same reference numerals are given to the same configurations as those of the power convertor according to the fifth embodiment illustrated in Fig. 7.
A power convertor 105 according to the sixth embodiment
includes a plurality of inverter units 3 (3a, 3b, 3c, •••) in the power convertor 104 according to the fifth embodiment.
In the embodiment, an output estimator 74 estimates an accurate detection value for a detection target of an abnormal DC voltage detector based on detection values from a plurality of DC voltage detectors 25, 26, 35 (35a, 35b, 35c, •••), and 36 (36a, 36b, 36c, •••). In the sixth embodiment, a plurality of methods for estimating the accurate detection value for the detection target of one abnormal DC voltage detector are present as follows.
In the power convertor 105, if each DC voltage detector is in a normal state, a relationship, in which a combined DC voltage value obtained by adding the detection values of the convertor-side DC voltage detectors 25 and 26 coincides with the combined DC voltage value obtained by adding the detection value of each of the inverter-side DC voltage detectors 35
30

(35a, 35b, 35c, •••), and 36 (36a, 36b, 36c, •••), is present. This indicates that there are a plurality of candidates for obtaining the combined DC voltage value necessary for estimating the detection value. As described above, since the candidates for obtaining the combined DC voltage value are increased, it is possible to improve a possibility capable of estimating the detection value of the detection target of the abnormal DC voltage detector.
According to the output estimator 74 in the embodiment, in a case where any one of the DC voltage detectors is abnormal, it is possible to estimate the accurate detection value of the detection target of the abnormal DC voltage detector by subtracting the detection value of one good DC voltage detector disposed on the same side as the abnormal DC voltage detector from the combined DC voltage value obtained by adding detection values of any two good DC voltage detectors on the convertor side or the inverter side.
Therefore, for example, even in a case where any one of the DC voltage detectors on the inverter side is abnormal and in a case where one DC voltage detector on the convertor side is abnormal, if any two DC voltage detectors on the inverter side are good, it is possible to estimate the accurate detection value for the detection target of one abnormal DC voltage detector on the inverter side by using the combined DC voltage value obtained by adding the detection values of the two DC
31

voltage detectors.
Also in the power convertor 105, it is possible to appropriately determine the abnormality of the DC voltage detector by the same process as that of the power convertor 100 according to the first embodiment. In addition, also in the power convertor 105, similar to the power convertor 104 according to the fifth embodiment, it is possible to appropriately estimate the detection value of the detection target of the abnormal DC voltage detector from detection values of a plurality of good DC voltage detectors.
In the sixth embodiment, the power convertor 105 includes the plurality of the inverter units 3 but, for example, may include a plurality of the convertor units 2. Even in the case, similar to the above description, it is possible to appropriately determine the abnormality of the DC voltage detector and to appropriately estimate the detection value of the detection target of the abnormal DC voltage detector from the detection values of the plurality of the good DC voltage detectors. In addition, candidates for obtaining the combined DC voltage value necessary for estimating the detection value of the detection target of the abnormal DC voltage detector can be extended to any two DC voltage detectors on the convertor side and it is possible to improve the possibility capable of estimating the detection value of the detection target of the abnormal DC voltage detector.
32

The invention is not limited to the above-described embodiments, but can be appropriately modified and implemented without departing from the spirit of the invention.
For example, in the embodiments, a part or all of the processes performed by the abnormality determiner 72 and the output estimator 74 may be performed by a hardware circuit.
In addition, in any of the above-described embodiments, the abnormality determiner 72 stores a history (for example, the execution date and time, and the detection value) of the detection value obtained by the DC voltage detector during the plurality of charging operations, grasps the change of the detection value obtained by the DC voltage detector, predicts a period until the detection value obtained by the DC voltage detector exceeds a predetermined threshold for determining abnormality, that is, a period until the abnormality occurs, and may display the prediction result on the displayer 73 based on the history of the detection values. Therefore, it is possible to grasp beforehand the timing of abnormality occurrence, and to prepare for prevention of the occurrence of the abnormality and for measures at the time of occurrence of the abnormality in advance.

WE CLAIM:

1.A power convertor that includes a convertor that
converts an AC power into a plurality of potentials of DC power,
and an inverter that converts a plurality of potentials of DC
power into an AC power, the power convertor comprising:
a smoothing capacitor that is connected between two potentials of a plurality of potentials and suppresses a potential fluctuation between the potentials;
a DC voltage detector that detects a potential difference between potentials to which the smoothing capacitor is connected; and
an abnormality determiner that determines an abnormality of the DC voltage detector based on a detection value obtained by the DC voltage detector during charging of the smoothing capacitor.
2. The power convertor according to claim 1,
wherein the abnormality determiner includes a storage
unit that stores a detection value of a reference value of the DC voltage detector during charging of the smoothing capacitor, and
wherein the abnormality determiner determines an abnormality of the DC voltage detector based on the reference value stored in the storage unit and the detection value.
3. The power convertor according to claim 2,

wherein the abnormality determiner stores the detection value of the DC voltage detector in the storage unit as the reference value during charging of the smoothing capacitor at a predetermined time point.
4. The power convertor according to claim 2 or 3,
wherein the abnormality determiner stores the reference
value of the detection values of the DC voltage detector in the storage unit at a plurality of time points during the charging.
5. The power convertor according to any one of claims
2 to 4,
wherein the abnormality determiner acquires voltage information indicating a charging voltage during the charging, calculates a correction reference value that is obtained by correcting the reference value based on the voltage information, and determines an abnormality of the DC voltage detector based on the correction reference value.
6. The power convertor according to any one of claims
1 to 5,
wherein the smoothing capacitor includes a convertor-side smoothing capacitor that is connected between two potentials of a plurality of potentials on the convertor side and an inverter-side smoothing capacitor that is connected between two potentials of a plurality of potentials on the inverter side,

wherein the DC voltage detector includes a convertor-side DC voltage detector that detects a potential difference between potentials to which the convertor-side smoothing capacitor is connected and an inverter-side DC voltage detector that detects a potential difference between potentials to which the inverter-side smoothing capacitor is connected, and
wherein the abnormality determiner determines an abnormality of the convertor-side DC voltage detector and the inverter-side DC voltage detector based on a detection value obtained by the convertor-side DC voltage detector and a detection value obtained by the inverter-side DC voltage detector when the convertor-side smoothing capacitor and the inverter-side smoothing capacitor are charged.
7. The power convertor according to any one of claims 1 to 5,
wherein the convertor converts the AC power into a first potential, a second potential that is lower than the first potential, and a third potential that is lower than the second potential,
wherein the inverter converts the first potential, the second potential, and the third potential of DC power into an AC power, and includes
a first smoothing capacitor that is connected between the first potential and the second potential,

a second smoothing capacitor that is connected between the second potential and the third potential,
a first DC voltage detector that detects a potential difference between potentials to which the first smoothing capacitor is connected, and
a second DC voltage detector that detects a potential difference between potentials to which the second smoothing capacitor is connected, and
wherein the abnormality determiner determines an abnormality of the first DC voltage detector and the second DC voltage detector based on detection values by the first DC voltage detector and the second DC voltage detector when the first smoothing capacitor and the second smoothing capacitor are charged.
8. The power convertor according to claim 7,
wherein in a case where a voltage value obtained by the
first DC voltage detector and the second DC voltage detector is zero or a value close to zero at a plurality of the time points during the charging, the abnormality determiner determines that a charging circuit is abnormal.
9. The power convertor according to claim 7,
wherein in a case where a voltage value obtained by one
of the first DC voltage detector and the second DC voltage detector is zero or a value close to zero at a plurality of the time points during the charging, the abnormality

determiner determines that wiring connected to the DC voltage detector is abnormal.
10. The power convertor according to any one of claims 7 to 9, further comprising:
a resistor that is connected between a second potential on the inverter side and a second potential on the convertor side,
wherein the first smoothing capacitor includes a first convertor-side smoothing capacitor that is connected between the first potential and the second potential on the convertor side, and a first inverter-side smoothing capacitor that is connected between the first potential and the second potential on the inverter side,
wherein the second smoothing capacitor includes a second convertor-side smoothing capacitor that is connected between the second potential and the third potential on the convertor side, and a second inverter-side smoothing capacitor that is connected between the second potential and the third potential on the inverter side,
wherein the first DC voltage detector includes a first convertor-side DC voltage detector that detects a potential difference between potentials to which the first convertor-side smoothing capacitor is connected and a first inverter-side DC voltage detector that detects a potential difference between potentials to which the first inverter-side

smoothing capacitor is connected,
wherein the second DC voltage detector includes a second convertor-side DC voltage detector that detects a potential difference between potentials to which the second convertor-side smoothing capacitor is connected and a second inverter-side DC voltage detector that detects a potential difference between potentials to which the second inverter-side smoothing capacitor is connected, and
wherein the abnormality determiner determines abnormality of the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector based on detection values obtained by the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector when the first convertor-side smoothing capacitor, the second convertor-side smoothing capacitor, the first inverter-side smoothing capacitor, and the second inverter-side smoothing capacitor are charged.
11. The power convertor according to claim 10,
wherein the abnormality determiner compares the detection values obtained by the first convertor-side DC voltage detector, the second convertor-side DC voltage

detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector with each other to specify a DC voltage detector having an abnormality in the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, or the second inverter-side DC voltage detector.
12. The power convertor according to claim 10 or 11,
further comprising:
an output estimation unit that estimates a detection value of a detection target of the DC voltage detector in which the abnormality is generated based on the detection values obtained by the first convertor-side DC voltage detector, the second convertor-side DC voltage detector, the first inverter-side DC voltage detector, and the second inverter-side DC voltage detector.
13. The power convertor according to any one of claims
1 to 12,
wherein in a case where it is determined that the abnormality is generated, the abnormality determiner displays information related to the abnormality on a display device.
14. The power convertor according to claim 13,
wherein the abnormality determiner stores an history of
the detection value obtained by the DC voltage detector during a plurality of times of charging, predicts a period until the abnormality of the DC voltage detector is generated based on

the history of the detection value, and displays a prediction result on the display device.
15. A abnormality detection method in a power convertor including a convertor that converts an AC power into a plurality of potentials of DC power, an inverter that converts a plurality of potentials into an AC power, a smoothing capacitor that is connected between two potentials of a plurality of potentials and suppresses a potential fluctuation between the potentials, and a DC voltage detector that detects a potential difference between potentials to which the smoothing capacitor is connected, the method comprising:
acquiring a detection value obtained by the DC voltage detector during charging of the smoothing capacitor; and
determining an abnormality of the DC voltage detector based on the acquired detection value.