[Title of Invention] POWER CONVERSION DEVICE AND ABNORMAL DETECTION METHOD [Technical Field] [0001]
The present invention relates to a power conversion device and an abnormal detection method. [Background Art] [0002]
A power conversion device that converts power of an alternating current (AC) power supply into power of a variable voltage variable frequency has been known. The power conversion device includes a smoothing capacitor in a direct current (DC) circuit and a DC voltage detector that measures a voltage across the smoothing capacitor, and exchanges power with an AC system connected thereto to control a DC voltage to be constant.
For example, as a technology for checking soundness of a DC voltage detector, a technology for determining an abnormality based on a plurality of signals during operation has been known (see Patent Document 1). [Prior Art Document] [Patent Document] [0003]
[Patent Document 1] JP 2019-195231 A [Summary of the Invention] [Problem to be Solved by the Invention]

[0004]
Patent Document 1 describes a technology for determining an abnormality by creating a plurality of diagnostic indicators from a DC voltage behavior during operation in order to check the soundness of the DC voltage detector and comparing the plurality of diagnostic indicators with a reference value, but does not disclose a technology for setting a reference value when a circuit constant of a motor or a transformer connected to an outside of a power conversion device of an application destination is unknown In addition, in the technology of Patent Document 1, even if the circuit constant of the motor or transformer connected to the outside of the power conversion device of the application destination is known, since the amount of change in the indicator for abnormalities in the DC voltage detector changes depending on the circuit constant, it is necessary to set reference values for each application destination. The DC voltage detector is indispensable for controlling the DC voltage of the power conversion device, and the abnormality in the DC voltage detector causes the operation of the system to become unstable, and in the worst case, the system may unexpectedly stop, and thus there is a risk of causing serious damage. [0005]
The present invention has been made in view of such circumstances, and provides a technology capable of appropriately detecting an abnormality in a DC voltage detector in a power conversion device even if a circuit constant of a

circuit connected to an outside of the power conversion device
is unknown.
[Means for solving the Problems]
[0006]
In order to solve the above problems, according to an aspect, there is provided a power conversion device including a converter that converts an alternating current into a first potential, a second potential lower than the first potential, and a third potential lower than the second potential, and an inverter that converts voltages of the first potential, the second potential, and the third potential into the alternating current, the power conversion device including: 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 the potentials to which the first smoothing capacitor is connected; a second DC voltage detector that detects a potential difference between the potentials to which the second smoothing capacitor is connected; a first type indicator calculator that calculates a first type indicator for diagnosing presence or absence of an abnormality of DC voltage detector by an indicator using a detection value of DC voltage detector based on a voltage relational expression that is established in a circuit including the potential difference between the potentials to which the first smoothing capacitor is connected and the potential difference between the

potentials to which the second smoothing capacitor is connected when a detection abnormality in which a detected value changes in a predetermined direction occurs in either the first DC voltage detector or the second DC voltage detector; a second type indicator calculator that appears as the change in the indicator when the detection abnormality in which the detected value changes in the predetermined direction occurs in either the first DC voltage detector or the second DC voltage detector; a comprehensive diagnosis indicator calculator that calculates a comprehensive diagnosis indicator by scalar synthesis or vector synthesis of one or two or more second type indicators; and an abnormal determination unit that assumes the number of DC voltage detectors, in which the abnormality occurs from the first DC voltage detector or the second DC voltage detector, to be one, performs an operation of switching the detected value of the DC voltage detector assumed to be abnormal to an output estimation value estimated based on a detected value of another DC voltage detector on one or two or more DC voltage detectors, and determines one of the first DC voltage detector or the second DC voltage detector in which the abnormality occurs based on the change in the comprehensive diagnosis indicator after the operation of switching to the output estimation value is performed.
[Effect of the Invention] [0007]
According to the present invention, even if the circuit constant of the circuit connected to the outside of the power

conversion device is unknown, the abnormality in the DC voltage
detector in the power conversion device can be appropriately
detected.
[Brief Description of the Drawings]
[0008]
FIG. 1 is an overall configuration diagram of a power conversion system according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of an abnormal determiner according to a first embodiment.
FIG. 3 is a configuration diagram of an indicator preparing unit according to a first embodiment.
FIG. 4 is a configuration diagram of a first indicator preparing unit according to the first embodiment.
FIG. 5 is a configuration diagram of a second indicator preparing unit according to the first embodiment.
FIG. 6 is a configuration diagram of a third indicator preparing unit according to the first embodiment.
FIG. 7A is a first diagram (part 1) for describing a second harmonic according to the first embodiment.
FIG. 7B is a first diagram (part 2) for describing the second harmonic according to the first embodiment.
FIG. 8A is a second diagram (part 1) for describing the second harmonic according to the first embodiment.
FIG. 8B is a second diagram (part 2) for describing the second harmonic according to the first embodiment.
FIG. 9 is a configuration diagram of a fourth indicator

preparing unit according to the first embodiment.
FIG. 10 is a configuration diagram of a fifth indicator preparing unit according to the first embodiment.
FIG. 11 is a configuration diagram of a sixth indicator preparing unit according to the first embodiment.
FIG. 12 is a configuration diagram of a seventh indicator preparing unit according to the first embodiment.
FIG. 13 is a diagram illustrating an extraction of a determination cross section according to the first embodiment.
FIG. 14A is a table illustrating an abnormal detector, a gain of the abnormal detector, and a change in an indicator
201 according to the first embodiment.
FIG. 14B is a table illustrating the abnormal detector, the gain of the abnormal detector, and a change in an indicator
202 according to the first embodiment.
FIG. 14C is a table illustrating the abnormal detector, the gain of the abnormal detector, and a change in indicators
203 and 204 according to the first embodiment.
FIG. 15A is a table illustrating the abnormal detector, the gain of the abnormal detector, and a change in an indicator
205 according to the first embodiment.
FIG. 15B is a table illustrating the abnormal detector, the gain of the abnormal detector, and a change in indicators
206 and 207 according to the first embodiment.
FIG. 16 is a diagram summarizing a relationship between the abnormal detector, an indicator, a converter-side indicator, and an inverter-side indicator according to the first

embodiment.
FIG. 17 is a configuration diagram of a DC voltage signal generation unit according to the first embodiment.
FIG. 18 is a flowchart of an abnormal location diagnosis process by an abnormal determiner according to the first embodiment.
FIG. 19 is a flowchart of the abnormal location diagnosis process by the abnormal determiner according to the first embodiment.
FIG. 20 is a diagram illustrating a state of the DC voltage detector when the DC voltage detector is abnormal in each time range by the abnormal determiner according to the first embodiment, the corresponding flowchart number, and an input of a correction unit.
FIG. 21A is a diagram illustrating an example of time change of the indicator 201 by the abnormal determiner according to the first embodiment.
FIG. 21B is a diagram illustrating an example of time change of the indicator 203 (converter-side indicator) by the abnormal determiner according to the first embodiment.
FIG. 21C is a diagram illustrating an example of time change of the indicator 206 (inverter-side indicator) by the abnormal determiner according to the first embodiment.
FIG. 21D is a diagram illustrating an example of time change of a comprehensive diagnosis indicator 250 by the abnormal determiner according to the first embodiment.
FIG. 22 is a diagram illustrating an operation example

when the DC voltage detector according to the first embodiment is abnormal.
FIG. 23A is a diagram illustrating an example of time change of the indicator 201 when the DC voltage detector according to the first embodiment is abnormal.
FIG. 23B is a diagram illustrating an example of time change of the indicator 203 (converter-side indicator) when the DC voltage detector according to the first embodiment is abnormal.
FIG. 23C is a diagram illustrating an example of time change of the indicator 206 (inverter-side indicator) when the DC voltage detector according to the first embodiment is abnormal.
FIG. 23D is a diagram illustrating an example of time change of the comprehensive diagnosis indicator when the DC voltage detector according to the first embodiment is abnormal.
FIG. 24A is a diagram illustrating a vector quantity of a comprehensive diagnosis indicator when the DC voltage detector according to a second embodiment of the present invention is normal (to to ti) .
FIG. 24B is a diagram illustrating a vector quantity of a comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when the estimated value is not used (t2 to t3) .
FIG. 24C is a diagram illustrating a vector quantity of a comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when

EFBH CP is used (t3 to t4) .
FIG. 24D is a diagram illustrating a vector quantity of a comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when EFBH_cN is used (t5 to t6) .
FIG. 24E is a diagram illustrating a vector quantity of a comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when EFBH IP is used (t7 to t8) .
FIG. 24F is a diagram illustrating a vector quantity of a comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when EFBH_IN is used (t9 to tio) .
FIG. 25A is a diagram illustrating the vector quantity of the comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment of the present invention is normal (to to ti) .
FIG. 25B is a diagram illustrating the vector quantity of the comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when the estimated value is not used (t2 to t3) .
FIG. 25C is a diagram illustrating the vector quantity of the comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when EFBH CP is used (t3 to t4) .
FIG. 25D is a diagram illustrating the vector quantity of the comprehensive diagnosis indicator when the DC voltage

detector according to the second embodiment is abnormal and when EFBH_cN is used (t5 to t6) .
FIG. 25E is a diagram illustrating the vector quantity of the comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when EFBH IP is used (t7 to t8) .
FIG. 25F is a diagram illustrating the vector quantity of the comprehensive diagnosis indicator when the DC voltage detector according to the second embodiment is abnormal and when EFBH_IN is used (t9 to tio) .
FIG. 26 is a flowchart of an abnormal location diagnosis process by an abnormal determiner of a power conversion device according to a third embodiment of the present invention.
FIG. 27 is a flowchart of an abnormal location diagnosis process by the abnormal determiner of the power conversion device according to the third embodiment.
FIG. 28 is a diagram illustrating an example of an operation example of the power conversion device according to the third embodiment.
FIG. 29A is a diagram illustrating an example of time change of the indicator 201 by the abnormal determiner of the power conversion device according to the third embodiment.
FIG. 29B is a diagram illustrating an example of time change of the indicator 203 (converter-side indicator) of the power conversion device according to the third embodiment.
FIG. 29C is a diagram illustrating an example of time change of the indicator 206 (inverter-side indicator) of the

power conversion device according to the third embodiment.
FIG. 29D is a diagram illustrating a time change example of a comprehensive diagnosis indicator of the power conversion device according to the third embodiment.
FIG. 30 is a flowchart of an abnormal location diagnosis process by an abnormal determiner of a power conversion device according to a fourth embodiment of the present invention.
FIG. 31 is a flowchart of the abnormal location diagnosis process by the abnormal determiner of the power conversion device according to the fourth embodiment.
FIG. 32A is a diagram illustrating an example of time change of the indicator 201 by the abnormal determiner of the power conversion device according to the fourth embodiment.
FIG. 32B is a diagram illustrating a time change example of the indicator 203 (converter-side indicator) of the power conversion device according to the fourth embodiment.
FIG. 32C is a diagram illustrating an example of time change of the indicator 206 (inverter-side indicator) of the power conversion device according to the fourth embodiment.
FIG. 32D is a diagram illustrating a time change example of a comprehensive diagnosis indicator of the power conversion device according to the fourth embodiment.
FIG. 33 is a diagram illustrating a first operation example of the power conversion device according to the fourth embodiment.
FIG. 34A is a diagram illustrating an example of time change of the indicator 201 by the abnormal determiner of the

power conversion device according to the fourth embodiment.
FIG. 34B is a diagram illustrating a time change example of the indicator 203 (converter-side indicator) of the power conversion device according to the fourth embodiment.
FIG. 34C is a diagram illustrating an example of time change of the indicator 206 (inverter-side indicator) of the power conversion device according to the fourth embodiment.
FIG. 34D is a diagram illustrating a time change example of a comprehensive diagnosis indicator of the power conversion device according to the fourth embodiment.
FIG. 35 is a diagram illustrating a second operation example of the power conversion device according to the fourth embodiment.
FIG. 36 is an overall configuration diagram of a power conversion system according to a fifth embodiment of the present invention.
FIG. 37 is an overall configuration diagram of a power conversion system according to a sixth embodiment of the present invention.
FIG. 38 is a configuration diagram of an abnormal determiner according to the sixth embodiment.
FIG. 39 is a configuration diagram of an indicator preparing unit according to the sixth embodiment.
FIG. 40 is a configuration diagram of an eighth indicator preparing unit according to the sixth embodiment.
FIG. 41A is a first diagram for describing the change due to the detector abnormality of the indicator according to the

sixth embodiment, in which when one of the DC voltage detectors fails, a DC voltage detector having abnormality, a direction of gain abnormality and a direction of change of the indicator
202 are illustrated.
FIG. 41B is a first diagram for describing the change due to the detector abnormality of the indicator according to the sixth embodiment, in which when one of the DC voltage detectors fails, a DC voltage detector having abnormality, a direction of gain abnormality and a direction of change of the indicators
203 and 204 are illustrated.
FIG. 41C is a first diagram for describing the change due to the detector abnormality of the indicator according to the sixth embodiment, in which when one of the DC voltage detectors fails, a DC voltage detector having abnormality, a direction of gain abnormality and a direction of change of the indicator 205 are illustrated.
FIG. 42A is a second diagram illustrating a change due to a detector abnormality of the indicator according to the sixth embodiment, in which when either the DC voltage detector 43 or 44 fails, a DC voltage detector having abnormality, a direction of gain abnormality and a direction of change of the indicators 206 and 207 are illustrated.
FIG. 42B is a second diagram illustrating a change due to a detector abnormality of the indicator according to the sixth embodiment, in which when either the DC voltage detector 43 or 44 fails, a DC voltage detector having abnormality, a direction of gain abnormality and a direction of change of the

indicator 208 are illustrated.
FIG. 43 is a configuration diagram of an estimation unit according to the sixth embodiment.
FIG. 44 is a flowchart of the abnormal location diagnosis process by the abnormal determiner according to the sixth embodiment.
FIG. 45 is a flowchart of the abnormal location diagnosis process by the abnormal determiner according to the sixth embodiment.
FIG. 46A is a diagram illustrating an estimated value use ratio KCIP when the DC voltage detector according to the sixth embodiment is abnormal.
FIG. 46B is a diagram illustrating an estimated value use ratio KCIN when the DC voltage detector according to the sixth embodiment is abnormal.
FIG. 46C is a diagram illustrating an indicator 209 when the DC voltage detector according to the sixth embodiment is abnormal.
FIG. 46D is a diagram illustrating the comprehensive diagnosis indicator when the DC voltage detector according to the sixth embodiment is abnormal.
FIG. 47A is a diagram illustrating an estimated value use ratio KCIP when the DC voltage detector according to the sixth embodiment is abnormal.
FIG. 47B is a diagram illustrating an estimated value use ratio KCIN when the DC voltage detector according to the sixth embodiment is abnormal.

FIG. 47C is a diagram illustrating an indicator 209 when the DC voltage detector according to the sixth embodiment is abnormal.
FIG. 47D is a diagram illustrating the comprehensive diagnosis indicator when the DC voltage detector according to the sixth embodiment is abnormal.
FIG. 48 is a configuration diagram of an indicator preparing unit of a power conversion device according to a modification of the first embodiment.
FIG. 49 is a diagram illustrating an example of a configuration of a ninth indicator preparing unit of the power conversion device according to the modification of the first embodiment.
FIG. 50A is a diagram illustrating an analysis result of a Q-axis current when a DC voltage detector is normal by a ninth indicator preparing unit of the power conversion device according to the modification of the first embodiment.
FIG. 50B is a diagram illustrating the analysis result of the Q-axis current at the time of an abnormality by the ninth indicator preparing unit of the power conversion device according to the modification of the first embodiment.
FIG. 51 is a diagram illustrating an example of a configuration of a tenth indicator preparing unit of the power conversion device according to the modification of the first embodiment.
FIG. 52A is a diagram illustrating an analysis result of a Q-axis current when a DC voltage detector is normal by the

tenth indicator preparing unit of the power conversion device according to the modification of the first embodiment.
FIG. 52B is a diagram illustrating the analysis result of the Q-axis current at the time of an abnormality by the tenth indicator preparing unit of the power conversion device according to the modification of the first embodiment.
FIG. 53A is a table showing the abnormal detector of the power conversion device, the gain of the abnormal detector, and the change of the indicator 209 according to the modification of the first embodiment.
FIG. 53B is a table showing the abnormal detector of the power conversion device, the gain of the abnormal detector, and the change of the indicator 210 according to the modification of the first embodiment.
[Best mode for carrying out the Invention] [0009]
Some embodiments will be described with reference to the drawings. It should be noted that the embodiments described below do not limit the invention according to the claims, and all of the elements and combinations thereof described in the embodiments are not essential for the means for solving the invention. (First Embodiment)
A power conversion system according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 25.
FIG. 1 is an overall configuration diagram of the power

conversion system according to the first embodiment.
A power conversion system 1000 includes an AC power supply 1 that supplies AC power, a power conversion device 100 that converts and outputs the AC power supplied from the AC power supply 1 into desired AC power, and an electric motor 4 that operates by the AC power output from the power conversion device 100. The power conversion device 100 and the electric motor 4 are connected via, for example, an AC cable.
[0010]
The power conversion device 100 includes a transformer 12 that transforms AC power, a converter unit (also called a converter) 2 that is connected to the AC power supply 1 via the transformer 12 and converts the AC power from the AC power supply 1 into DC power, an inverter unit (also called an inverter) 3 that converts the DC power output from the converter unit 2 into desiredAC power and outputs the desired AC power to the electric motor 4, a converter control device 5 that controls the converter unit 2, and an inverter control device 6 that controls the inverter unit 3.
[0011]
The converter unit 2 is a neutral point clamp type three-level converter, and converts an AC voltage to a DC voltage with 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 converter, and converts the DC voltage with the positive potential (first potential) level,

the neutral point (zero) potential (second potential) level, and the negative potential (third potential) level into the AC voltage for the electric motor 4 . The positive potential levels of the converter unit 2 and the inverter unit 3 are connected by a P wiring 40, the neutral point potential levels thereof are connected by a C wiring 41, and the negative potential levels thereof are connected by an N wiring 42.
[0012]
The converter unit 2 includes a converter power conversion unit 21, a P-side smoothing capacitor 22 (first smoothing capacitor, converter-side first smoothing capacitor) of the converter 2 for suppressing a fluctuation in DC voltage, an N-side smoothing capacitor 23 (second smoothing capacitor, converter-side second smoothing capacitor) of the converter 2, a DC voltage detector 25 (first DC voltage detector, converter-side first DC voltage detector) for measuring a voltage between terminals of the smoothing capacitor 22, a DC voltage detector 26 (second DC voltage detector, converter-side second DC voltage detector) for measuring a voltage between terminals of the smoothing capacitor 23, and a converter neutral point resistor 24 for suppressing DC resonance. The converter neutral point resistor 24 is connected to the C wiring 41 . Note that although FIG. 1 illustrates only a configuration
(excluding the converter neutral point resistor 24, the DC voltage detector 25, and the DC voltage detector 26) for one phase of the converter unit 2, the same configuration is provided for other phases.

[0013]
The inverter unit 3 includes an inverter power conversion unit 31, a P-side smoothing capacitor 32 (first smoothing capacitor, inverter-side first smoothing capacitor) of the inverter 3, an N-side smoothing capacitor 33 (second smoothing capacitor, inverter-side second smoothing capacitor) of the inverter 3, a DC voltage detector 35 (first DC voltage detector, inverter-side first DC voltage detector) for measuring a voltage between terminals of the smoothing capacitor 32, a DC voltage detector 36 (second DC voltage detector, inverter-side second DC voltage detector) for measuring a voltage between terminals of the N-side smoothing capacitor 33 of the inverter 3, and an inverter neutral point resistor 34 for suppressing DC resonance. The inverter neutral point resistor 34 is connected to the C wiring 41. Note that although FIG. 1 illustrates only a configuration (excluding the inverter neutral point resistor 34, the DC voltage detector 35, and the DC voltage detector 36) for one phase of the inverter unit 3, the same configuration is provided for other phases. [0014]
The converter control device 5 controls the converter power conversion unit 21 so that the converted DC power becomes a desired value. The inverter control device 6 controls the inverter power conversion unit 31 so that an output torque and speed of the electric motor 4 satisfy desired characteristics. [0015]
The power conversion device 100 further includes a

current detector 7 as an example of an AC current detector that detects and outputs a current flowing between the converter unit 2 and the AC power supply 1, a voltage detector 11 as an example of an AC voltage detector that detects and outputs an output voltage of AC power supply 1, a speed detector 8 that is directly connected to the electric motor 4 and detects and outputs the speed of the electric motor 4, a current detector 9 that detects and outputs an output current of the inverter unit 3, a voltage detector 10 that detects and outputs an output voltage of the inverter unit 3, an abnormal determiner 72 (abnormal determination unit) as an example of the abnormal determination unit, and a display 73. [0016]
The detected value signals (output signals) detected by the current detector 7 and the DC voltage detectors 25 and 26 are input to the converter control device 5. The converter control device 5 performs various operation processes based on the input detected value, and outputs a signal for controlling the converter power conversion unit 21. [0017]
The detected value signals (output signals) detected by the speed detector 8, the current detector 9, and the DC voltage detectors 35 and 36 are input to the inverter control device 6. The inverter control device 6 performs various operation processes based on the input detected value, and outputs a signal for controlling the inverter power conversion unit 31 to the inverter power conversion unit 31.

[0018]
The detected value signals (output signals) detected by the current detector 7, the speed detector 8, the current detector 9, the voltage detector 11, the DC voltage detectors 25 and 26, and the DC voltage detectors 35 and 36 are input to the abnormal determiner 72. [0019]
The converter control device 5 includes a DC voltage command generator 51, a DC voltage control device 52, a current control device 53, a pulse generator 54, and a neutral point voltage controller 55 as an example of the converter neutral point control device. [0020]
The DC voltage command generator 51 outputs a DC voltage command value indicating the voltage value of the DC voltage output from the converter unit 2 to the DC voltage control device
52. Specifically, the DC voltage command generator 51 outputs
a command value of a P-N voltage output from the converter 2
which is a fixed value.
[0021]
The DC voltage control device 52 operates a converter output effective current command value based on the DC voltage command value input from the DC voltage command generator 51 and the detected value of the DC voltage input from the DC voltage detectors 25 and 26, and outputs the calculated converter output effective current command value to the current control device
53. Specifically, the DC voltage control device 52 operates

the converter output effective current command value so that a total value of the detected values of the DC voltage input from each of the DC voltage detectors 25 and 26 matches the DC voltage command value. [0022]
The neutral point voltage controller 55 calculates an AC output voltage correction value AVZR0UT C SO that the neutral point voltage becomes zero based on the difference in the detected values of the DC voltage input from each of the DC voltage detectors 25 and 26, and outputs the calculated AC output voltage correction value AVZR0UT C to the current control device 53. [0023]
The current control device 53 operates the converter AC voltage command value so that the detected value (converter output current detection value) input from the current detector 7 matches the converter output effective current command value input from the DC voltage control device 52, and outputs the operated converter AC voltage command value to the pulse generator 54. In this time, the current control device 53 adds the AC output voltage correction value AVZR0UT C input from the neutral point voltage controller 55 to the AC output voltage command value which is the output of the predetermined current control operation, and calculates the converter AC voltage command value. [0024]
The pulse generator 54 calculates a pulse signal for

on/off control of each switching element of the converter power conversion unit 21 by pulse width modulation of a triangular wave, which is a carrier wave, and the converter AC voltage command value so that the AC output voltage from the converter power conversion unit 21 matches the converter AC voltage command value input from the current control device 53, and outputs the pulse signal to the converter power conversion unit 21. [0025]
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 as an example of the inverter neutral point control device. [0026]
The speed command generator 61 outputs a speed command value indicating a speed at which the electric motor 4 is operated to the speed controller 62 . In the present embodiment, the speed command value is a predetermined value set in advance. [0027]
The speed controller 62 operates the inverter output current command value so that the detected value (speed detected value) input from the speed detector 8 matches the speed command value input from the speed command generator 61, and outputs the inverter output current command value to the current controller 63. [0028]
The neutral point voltage controller 65 operates the AC

output voltage correction value AVZR0UT I SO that the neutral point voltage becomes zero based on the difference in the detected values of the DC voltage input from each of the DC voltage detectors 35 and 36, and outputs the operated AC output voltage correction value AVZR0UT I to the current controller 63.
[0029]
The current controller 63 operates the inverter AC voltage command value so that the inverter output current detection value input from the current detector 9 matches the inverter output current command value input from the speed controller 62, and outputs the operated inverter AC voltage command value to the pulse generator 64. In this case, the current controller 63 adds the AC output voltage correction value AVZROUT i input from the neutral point voltage controller 65 to the AC output voltage command value, which is the output of the predetermined current control operation, and calculates the inverter AC voltage command value.
[0030]
The pulse generator 64 calculates a pulse signal for on/off control of each switching element of the inverter power conversion unit 31 by performing the pulse width modulation of the triangular wave, which is a carrier wave, and the inverter AC voltage command value so that the output voltage from the inverter power conversion unit 31 matches the inverter AC output voltage command value input from the current controller 63, and outputs the pulse signal to the inverter power conversion unit 31.

WE CLAIM: [Claim 1]
A power conversion device including a converter that converts an alternating current into a first potential, a second potential lower than the first potential, and a third potential lower than the second potential, and an inverter that converts voltages of the first potential, the second potential, and the third potential into the alternating current, the power conversion device comprising:
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 the potentials to which the first smoothing capacitor is connected;
a second DC voltage detector that detects a potential difference between the potentials to which the second smoothing capacitor is connected;
a first type indicator calculator that calculates a first type indicator for diagnosing presence or absence of an abnormality of DC voltage detector by an indicator using a detection value of the DC voltage detector based on a voltage relational expression that is established in a circuit including the potential difference between the potentials to which the first smoothing capacitor is connected and the potential difference between the potentials to which the second

smoothing capacitor is connected when a detection abnormality in which a detected value changes in a predetermined direction occurs in either the first DC voltage detector or the second DC voltage detector;
a second type indicator calculator that calculates a second type indicator that appears as the change in the indicator when the detection abnormality in which the detected value changes in the predetermined direction occurs in either the first DC voltage detector or the second DC voltage detector;
a comprehensive diagnosis indicator calculator that calculates a comprehensive diagnosis indicator by scalar synthesis or vector synthesis of one or two or more second type indicators; and
an abnormal determination unit that assumes the number of DC voltage detectors, in which the abnormality occurs from the first DC voltage detector or the second DC voltage detector, to be one, performs an operation of switching the detected value of the DC voltage detector assumed to be abnormal to an output estimation value estimated based on a detected value of another DC voltage detector on one or two or more DC voltage detectors, and determines one of the first DC voltage detector or the second DC voltage detector in which the abnormality occurs based on the change in the comprehensive diagnosis indicator after the operation of switching to the output estimation value is performed. [Claim 2]
The power conversion device according to claim 1, further

comprising:
a neutral point resistor that is connected between the second potential on the inverter side and the second potential on the converter side, and suppresses DC resonance,
wherein the first smoothing capacitor includes a converter-side first smoothing capacitor connected to the converter side of the neutral point resistor and an inverter-side first smoothing capacitor connected to the inverter side of the neutral point resistor,
the second smoothing capacitor includes a converter-side second smoothing capacitor connected to the converter side of the neutral point resistor and an inverter-side second smoothing capacitor connected to the inverter side of the neutral point resistor,
the first DC voltage detector includes a converter-side first DC voltage detector that detects the potential difference between the potentials to which the converter-side first smoothing capacitor is connected and an inverter-side first DC voltage detector that detects the potential difference between the potentials to which the inverter-side first smoothing capacitor is connected,
the second DC voltage detector includes a converter-side second DC voltage detector that detects the potential difference between the potentials to which the converter-side second smoothing capacitor is connected and an inverter-side second DC voltage detector that detects the potential difference between the potentials to which the inverter-side

second smoothing capacitor is connected,
the first type indicator is an indicator using the detected value of the DC voltage detector based on the voltage relational expression which is established in the circuit including the potential difference between the potentials to which the converter-side first smoothing capacitor is connected, the potential difference between the potentials to which the converter-side second smoothing capacitor is connected, the potential difference between the potentials to which the inverter-side first smoothing capacitor is connected, and the potential difference between the potentials to which the inverter-side second smoothing capacitor is connected, and
the second type indicator includes at least one of a converter-side indicator that appears as the change in the indicator when the detection abnormality in which the detected value changes in the predetermined direction occurs in either the converter-side first DC voltage detector or the converter-side second DC voltage detector or an inverter-side indicator that appears as the change in the indicator when the detection abnormality in which the detected value changes in the predetermined direction occurs in either the inverter-side first DC voltage detector or the inverter-side second DC voltage detector. [Claim 3]
The power conversion device according to claim 1, wherein
a neutral point resistor for suppressing DC resonance is not connected between the second potential on the inverter side

and the second potential on the converter side,
the first smoothing capacitor includes a converter-side first smoothing capacitor connected to the converter side and an inverter-side first smoothing capacitor connected to the inverter side,
the second smoothing capacitor includes a converter-side second smoothing capacitor connected to the converter side and an inverter-side second smoothing capacitor connected to the inverter side,
the power conversion device further includes a third DC voltage detector that detects the potential difference between the potentials to which the first smoothing capacitor and the second smoothing capacitor are connected, and
the first type indicator calculator is an indicator using the detected value of the DC voltage detector based on the voltage relational expression that is established at a location including the potential difference between the potentials to which the first smoothing capacitor is connected, the potential difference between the potentials to which the second smoothing capacitor is connected, and the potential difference between the potentials to which the first smoothing capacitor and the second smoothing capacitor are connected. [Claim 4]
The power conversion device according to claim 2, wherein the first type indicator calculator calculates an inverter-converter voltage detection value difference indicator, which is an indicator, as the first type indicator

based on a difference between a sum of voltage values detected by the converter-side first DC voltage detector and the converter-side second DC voltage detector and a sum of voltage values detected by the inverter-side first DC voltage detector and the inverter-side second DC voltage detector. [Claim 5]
The power conversion device according to claim 2, wherein
the first type indicator calculator includes a third DC voltage detector that measures a total voltage of the first DC voltage detector and the second DC voltage detector, and calculates a first and second smoothing capacitor voltage detection value difference indicator, which is an indicator, as the first type indicator based on a difference between a sum of a voltage value of the first DC voltage detector and a voltage value detected by the second DC voltage detector and a voltage value of the third DC voltage detector. [Claim 6]
The power conversion device according to claim 2 or 3, further comprising:
a converter neutral point control device that generates a command value for adjusting a potential of the second potential of the converter to zero based on a difference between voltage values detected by the first DC voltage detector and the second DC voltage detector,
wherein the second type indicator calculator calculates a converter neutral point voltage control signal indicator based on the command value as the second type indicator.

[Claim 7]
The power conversion device according to claim 2 or 3, further comprising:
an AC current detector that detects a current at a position of a power supply side of the converter,
wherein the second type indicator calculator calculates a reference even-order harmonic waveform for a current at a position on the power supply side, and calculates a converter-side even-order harmonic current indicator, which is an indicator, as the second type indicator based on a product of the reference even-order harmonic waveform and a current value detected by the AC current detector. [Claim 8]
The power conversion device according to claim 2 or 3, further comprising:
an AC voltage detector that detects a voltage at a position of a power supply side of the converter,
wherein the second type indicator calculator
calculates a reference even-order harmonic waveform for the voltage at the position of the power supply side and calculates a converter-side even-order harmonic voltage indicator, which is an indicator, as the second type indicator based on a product of the reference even-order harmonic waveform and the voltage value detected at the position of the power supply side. [Claim 9]
The power conversion device according to claim 2 or 3,

further comprising:
an inverter neutral point control device that generates a command value for adjusting a potential of the second potential of the inverter to zero based on a difference between voltage values detected by the first DC voltage detector and the second DC voltage detector,
wherein the second type indicator calculator calculates an inverter neutral point voltage control signal indicator based on the command value as the second type indicator. [Claim 10]
The power conversion device according to claim 2 or 3, further comprising:
a current detector that detects a current at a position of a load side of the inverter,
wherein the second type indicator calculator
calculates a reference even-order harmonic waveform for the current at the position of the load side, and calculates an inverter-side even-order harmonic current indicator, which is an indicator, as the second type indicator based on a product of the reference even-order harmonic waveform and the current value detected by the current detector. [Claim 11]
The power conversion device according to claim 2 or 3, wherein
the alternating current of the inverter side is a three-phase alternating current including a U phase, a V phase, and a W phase,

the power conversion device further includes an AC voltage detector that detects a voltage of each phase of the inverter, and
the second type indicator calculator calculates an AC line voltage indicator as the second type indicator based on a difference between a first line voltage and a second line voltage when the first line voltage which is a voltage between the U phase and the V phase detected by the AC voltage detector and a second line voltage which is a voltage between the V phase and the W phase are both positive or negative. [Claim 12]
The power conversion device according to claim 2 or 4 or any one of claims 6 to 11, wherein
the abnormal determination unit stores a normal comprehensive diagnosis indicator when all the DC voltage devices are determined to be normal based on the first type indicator,
when any DC voltage device is determined to be abnormal based on the first type indicator,
performs an operation of assuming one of the converter-side first DC voltage detector, the converter-side second DC voltage detector, the inverter-side first DC voltage detector, or the inverter-side second DC voltage detector to be abnormal, switching a detected value of the DC voltage detector assumed to be abnormal to an output estimation value estimated based on a detected value of another DC voltage detector, and storing a comprehensive diagnosis indicator

(comprehensive diagnosis indicator at the time of switching the estimated value) at that time on all the DC voltage detectors, and
calculates a difference of the comprehensive diagnosis indicator at the time of switching the estimated value from the normal comprehensive diagnosis indicator and determines the DC voltage detector assumed to be abnormal when the difference is the smallest to be an abnormal DC voltage detector. [Claim 13]
The power conversion device according to claim 3 or any one of claims 5 to 11, wherein
the abnormal determination unit stores a normal comprehensive diagnosis indicator when all the DC voltage devices are determined to be normal based on the first type indicator,
when any DC voltage device is determined to be abnormal based on the first type indicator,
performs an operation of assuming one of the first type DC voltage detector or the second DC voltage detector to be abnormal, switching the detected value of the DC voltage detector assumed to be abnormal to the output estimation value estimated based on a detected value of another DC voltage detector, and storing a comprehensive diagnosis indicator (comprehensive diagnosis indicator at the time of switching the estimated value) at that time on all the DC voltage detectors, and
calculates a difference of the comprehensive diagnosis

indicator at the time of switching the estimated value from the normal comprehensive diagnosis indicator and determines the DC voltage detector assumed to be abnormal when the difference is the smallest to be an abnormal DC voltage detector. [Claim 14]
The power conversion device according to claim 12 or 13, wherein
the abnormal determination unit
further stores the abnormal comprehensive diagnosis indicator when any DC voltage device is determined to be abnormal based on the first type indicator,
further sets a reference value based on the normal comprehensive diagnosis indicator and the abnormal comprehensive diagnosis indicator, and
when any DC voltage device is determined to be abnormal based on the first type indicator,
if an operation of switching the detected value of the DC voltage detector assumed to be abnormal to the output estimation value estimated based on the detected value of another DC voltage detector and storing the comprehensive diagnosis indicator at that time is performed, in the case where the comprehensive diagnosis indicator is a value closer to the normal comprehensive diagnosis indicator than the above reference value, the DC voltage detector is determined to be an abnormal DC voltage detector at that time. [Claim 15]
The power conversion device according to claim 2 or 3,

further comprising:
an AC current detector that detects the current at the position on the power supply side of the converter,
wherein the second type indicator calculator
calculates the indicator as the second type indicator based on a carrier frequency component included in a fundamental wave Q-axis current of a current at a position on the power supply side. [Claim 16]
The power conversion device according to claim 2 or 3, further comprising:
a current detector that detects the current at a position on a load side of the inverter,
wherein the second type indicator calculator
calculates the indicator as the second type indicator based on a carrier frequency component included in a fundamental wave Q-axis current of a current at the position on the load side. [Claim 17]
The power conversion device according to claim 2 or 3, wherein
the abnormal determination unit detects whether or not the load at the position on the load side of the inverter is unloaded, and
when it is determined that the load is unloaded, or when it is determined that the load changes from loaded to unloaded,
performs an operation of switching the detected value of

the DC voltage detector assumed to be abnormal to the output estimation value or the output correction value. [Claim 18]
An abnormal detection method by a power conversion device including a converter that converts an alternating current into a first potential, a second potential lower than the first potential, and a third potential lower than the second potential, and an inverter that converts voltages of the first potential, the second potential, and the third potential into the alternating current,
wherein the power conversion device 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 the potentials to which the first smoothing capacitor is connected;
a second DC voltage detector that detects a potential difference between the potentials to which the second smoothing capacitor is connected;
a first type indicator calculator that calculates a first type indicator for diagnosing presence or absence of an abnormality of DC voltage detector by an indicator using a detected value of DC voltage detector based on a voltage relational expression that is established in a circuit including the potential difference between the potentials to

which the first smoothing capacitor is connected and the potential difference between the potentials to which the second smoothing capacitor is connected when a detection abnormality in which the detected value changes in a predetermined direction occurs in either the first DC voltage detector or the second DC voltage detector;
a second type indicator calculator that calculates a second type indicator that appears as the change in the indicator when the detection abnormality in which the detected value changes in the predetermined direction occurs in either the first DC voltage detector or the second DC voltage detector; and
a comprehensive diagnosis indicator calculator that calculates a comprehensive diagnosis indicator by scalar synthesis or vector synthesis of one or two or more second type indicators,
wherein the number of DC voltage detectors, in which the abnormality occurs from the first DC voltage detector or the second DC voltage detector, is assumed to be one, an operation of switching the detected value of the DC voltage detector assumed to be abnormal to an output estimation value estimated based on a detected value of another DC voltage detector is performed on one or two or more DC voltage detectors, and one of the first DC voltage detector or the second DC voltage detector in which the abnormality occurs is determined based on the change in the comprehensive diagnosis indicator after the operation of switching to the output estimation value is

performed.