CN115208273A

CN115208273A - Power conversion device and motor control method

Info

Publication number: CN115208273A
Application number: CN202210239415.9A
Authority: CN
Inventors: 秋田佳稔; 田村崇广
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2021-04-14
Filing date: 2022-03-11
Publication date: 2022-10-18
Also published as: JP2022163493A

Abstract

The invention provides a technique for correcting control with high precision without using an AC line voltage detector. The power conversion device includes: a converter; an inverter for converting voltages of a plurality of potentials into an alternating current output to the motor; a DC voltage detector for detecting a potential difference between 2 of the plurality of potentials as a DC voltage detection value; a current detector for detecting an output current of the inverter and outputting the detected output current as an inverter output current; an inverter output current controller for generating an inverter output voltage command to the inverter so that an inverter output current coincides with the inverter output current command; a motor voltage calculator for calculating a motor voltage estimated value, which is an estimated value of an ac line voltage of the motor, from the inverter output voltage command and the dc voltage detected value; a correction control unit for calculating a correction value for correcting a signal for controlling the motor based on the motor voltage estimation value; and an adder for adding the correction value to the control command signal to generate an inverter output current command.

Description

Power conversion device and motor control method

Technical Field

The present disclosure relates to a power conversion device including an inverter for driving a motor.

Background

As a power converter for driving a motor, a power conversion device is known which converts electric power of an ac power supply into electric power of variable frequency at variable voltage. The main circuit of the power conversion device is configured to include: a converter that converts alternating current to direct current; a DC circuit connected to the converter; and an inverter connected to the converter via a dc circuit and converting dc into ac, wherein the dc circuit includes a smoothing capacitor. The power conversion device controls the speed and torque of the motor by varying the magnitude and frequency of the ac voltage applied to the motor using an inverter.

As a control system of the motor, a speed control system and a current control system are used. The speed control system detects the speed of the motor through a speed detector and feeds back the detection value of the speed detector. The current control system detects a current flowing through the motor by a current detector and feeds back a detection value of the current detector. Further, there is a method of correcting a command value in order to improve the control accuracy of a motor (patent documents 1 and 2).

There is a method of detecting an ac line voltage of the motor by an ac line voltage detector and applying a correction to control using the detected value. For example, in the control of an induction motor, the slip amount and the speed electromotive force of the induction motor are controlled, but there is a risk of accuracy deterioration due to deviation of a design value such as resistance and mutual inductance of the motor from an actual value and characteristic change. Therefore, there is correction control in which a deviation amount between a design value and an actual value is extracted from a detection value of an ac line voltage of the motor, and a correction amount is added to a slip amount and an excitation current so that the deviation amount becomes zero.

Documents of the prior art

Patent document 1: japanese patent laid-open publication No. 2004-208397

Patent document 2: japanese laid-open patent publication No. H09-149658

Disclosure of Invention

Technical problem to be solved by the invention

In the above-described method of applying correction to control using the detected value of the ac line voltage, the ac line voltage detector detects the output voltage from the semiconductor element in the power converter. This output voltage is a rectangular wave accompanying switching, and a large ripple component is included in the detection value, and the accuracy may be deteriorated due to this ripple component.

In addition, in the case where a configuration is adopted in which the output of the filter circuit is detected using a filter circuit having a large time constant in order to reduce the large ripple component, a delay occurs in the detection of the output voltage, and there is a possibility that accuracy is deteriorated due to the delay.

In addition, in the configuration using the ac line-to-line voltage detector, an abnormality occurs in the ac line-to-line voltage detector, accuracy of correction control deteriorates, and an unplanned stop may occur in the worst case.

An object of the present invention is to provide a technique for performing highly accurate correction control without using an ac line voltage detector.

Another object of the present invention is to provide a technique for detecting an abnormality of an ac line-to-line voltage detector in a configuration using the ac line-to-line voltage detector.

Means for solving the problems

A power conversion device according to an aspect of the present invention includes: a converter that converts an alternating current input into a plurality of potentials; an inverter that converts the voltages at the plurality of potentials into an alternating current output to the motor; a smoothing capacitor connected between 2 of the plurality of potentials and configured to suppress potential variation between the potentials; a dc voltage detector that detects a potential difference between the potentials to which the smoothing capacitor is connected as a dc voltage detection value; a current detector that detects an output current of the inverter and outputs the output current as an inverter output current; an inverter output current controller that generates an inverter output voltage command for the inverter so that the inverter output current coincides with an inverter output current command; a motor voltage calculator that calculates a motor voltage estimated value that is an estimated value of an ac line voltage of the motor, based on the inverter output voltage command and the dc voltage detection value; a correction control unit that calculates a correction value for correcting a signal for controlling the motor based on the motor voltage estimation value; and an adder that adds the correction value to a control command signal to generate the inverter output current command.

A power conversion device according to another aspect of the present invention includes: a converter that converts an alternating current input into a plurality of potentials; an inverter that converts the voltages of the plurality of potentials into an alternating current output to a motor; a smoothing capacitor connected between 2 of the plurality of potentials and configured to suppress potential variation between the potentials; a dc voltage detector that detects a potential difference between potentials at which the smoothing capacitor is connected as a dc voltage detection value; an ac line voltage detector that detects an output voltage of the inverter and outputs the detected voltage as a motor voltage value; a correction control unit that calculates a correction value for correcting a signal for controlling the motor based on the motor voltage detection value; an adder that adds the correction value to a control command signal to generate an inverter output current command; a current detector that detects an output current of the inverter and outputs the output current as an inverter output current; an inverter output current controller that generates an inverter output voltage command for the inverter so that the inverter output current coincides with the inverter output current command; a motor voltage calculation unit that calculates a motor voltage estimated value that is an estimated value of an ac line voltage of the motor, based on the inverter output voltage command and the dc voltage detection value; and an abnormality determiner for determining an abnormality of the ac line-to-line voltage detector based on the estimated motor voltage value.

ADVANTAGEOUS EFFECTS OF INVENTION

According to one aspect of the present disclosure, since the estimated value of the ac line voltage of the motor is calculated from the inverter output voltage command and the dc voltage detection value, and the correction value for correcting the signal for controlling the motor is calculated from the estimated value, it is possible to perform highly accurate correction control without using the ac line-out voltage detector.

According to another aspect of the present disclosure, an estimated value of the ac line-to-line voltage of the motor is calculated from the inverter output voltage command and the dc voltage detection value, and an abnormality of the ac line-to-line voltage detector is determined based on the estimated value.

Drawings

Fig. 1 is an overall configuration diagram of a power converter of embodiment 1.

Fig. 2 is a diagram showing the magnetic flux saturation characteristics of the motor.

Fig. 3 is a diagram showing a relationship between speed, field current, and speed electromotive force.

Fig. 4 is a diagram showing a configuration of a conventional power conversion device for comparison with the power conversion device of the present embodiment.

Fig. 5 is a diagram for explaining the configuration of the 3-level motor voltage arithmetic unit 70.

Fig. 6 is a diagram illustrating a relationship between a voltage command and an output rectangular wave voltage in the bipolar state.

Fig. 7 is a diagram for explaining the 3-level bipolar modulation voltage arithmetic unit 71.

Fig. 8 is a diagram illustrating a relationship between a voltage command and an output rectangular wave voltage in unipolar modulation.

Fig. 9 is a diagram for explaining the 3-level unipolar modulation voltage operator 72.

Fig. 10 is an overall configuration diagram of a power converter of embodiment 2.

Fig. 11 is a diagram for explaining the 2-level motor voltage arithmetic unit 80.

Fig. 12 is a diagram for explaining the relationship between the voltage command and the output rectangular wave voltage in the case of 2 levels.

Fig. 13 is a diagram for explaining the 2-level modulation voltage arithmetic unit 81.

Fig. 14 is an overall configuration diagram of a power converter according to embodiment 3.

Fig. 15 is a flowchart of the abnormality diagnosis of the ac line voltage detector.

Fig. 16 is an overall configuration diagram of a power converter of embodiment 4.

Fig. 17 is a diagram for explaining the abnormal operation value switcher 92.

Description of the reference numerals

1 \8230, AC power supply 2 \8230, converter unit 3 \8230, inverter unit 4 \8230, motor 5 \8230, converter control device 6 \8230, inverter control device 7 \8230, current detector 8 \8230, speed detector 9 \8230, current detector 10 \8230, voltage detector between AC lines 11 \8230, filter circuit 21 \8230, converter power conversion part 22 \8230, smoothing capacitor on P side of converter 23 \8230, smoothing capacitor on N side of converter 24 \8230, neutral point resistance of converter 25 \8230, converter P side direct current voltage detector 26 \8230, converter N side direct current voltage detector 31 \8230, inverter power conversion part 32 \8230, inverter P side smoothing capacitor 33 \8230, inverter N side smoothing capacitor 34 \8230, inverter neutral point resistance 35 \8230, inverter P side direct current voltage detector 36 \8230, inverter N side direct current voltage detector 37 \8230, direct current voltage detector 40 \8230, P wiring 41 \8230, C wiring, and the like 42 \8230, N wiring, 51 \8230, DC voltage command generator, 52 \8230, DC voltage controller, 53 \8230, current controller, 54 \8230, pulse generator, 55 \8230, neutral point voltage controller, 61 \8230, speed command generator, 62 \8230, speed controller, 63 \8230, current controller, 64 \8230, pulse generator, 65 \8230, neutral point voltage controller, 66 \8230, exciting current command generator, 67 \8230, magnetic flux controller, 68 \8230, correction controller, 69 \8230, adder, 70 \8230, 3 level motor voltage calculator, 71 \8230, 3 level modulation voltage calculator, 72 \828230, 3 level modulation voltage calculator, 823080 \, 8280 \, and ac line voltage calculator, 8280 \ line voltage calculator, 823080, and 823080 \ line voltage calculator, and line-to line voltage calculator, 91\8230, a display 92 \8230, an abnormal time operation value switcher 100 \8230, a power conversion device 101 \8230, a power conversion device 102 \8230, a power conversion device 103 \8230, a power conversion device 104 \8230, a power conversion device 711 \8230, an Ep side pulse width operator 712 \8230, a direct current voltage variation operator 713 \8230, a correction amount operator 714 \8230, a bipolar motor phase voltage operator 721 8230, a direct current voltage variation ratio operator 722 \8230, a phase voltage operator 82723 \30, a unipolar motor phase voltage operator 811 \30, a direct current voltage variation ratio operator 812, and a phase voltage operator 8230.

Detailed Description

Several embodiments are described with reference to the accompanying drawings. 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 necessarily essential to the means for solving the problems of the invention.

[ example 1]

In embodiment 1, a power conversion device using a 3-level converter is exemplified.

Fig. 1 is an overall configuration diagram of a power converter according to embodiment 1.

The power conversion device 100 is a device that converts ac power from the ac power supply 1 to drive the motor 4. The power conversion device 100 includes: a converter unit (also referred to as a converter) 2 that converts alternating-current power from the alternating-current power supply 1 into direct-current power; an inverter unit (also referred to as an inverter) 3 that converts the dc power output from the converter unit 2 into desired ac power and drives the 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.

The converter unit 2 is a so-called 3-level converter that converts ac power into dc power at a positive potential (first potential) level, a neutral point (zero) potential (second potential) level, and a negative potential (third potential) level. The inverter unit 3 is a so-called 3-level inverter that converts dc power at a positive potential (first potential) level, a neutral point (zero) potential (second potential) level, and a negative potential (third potential) level into ac power for the motor 4. Between the converter unit 2 and the inverter unit 3, a positive potential level is connected by a P wiring 40, a neutral point potential level is connected by a C wiring 41, and a negative potential level is connected by an N wiring 42.

The converter unit 2 includes a converter power conversion unit 21, a converter P-side smoothing capacitor 22 and a converter N-side smoothing capacitor 23 for suppressing fluctuations in the dc voltage, a converter P-side dc voltage detector 25 for measuring the voltage between the terminals of the converter P-side smoothing capacitor 22, a converter N-side dc voltage detector 26 for measuring the voltage between the terminals of the converter N-side smoothing capacitor 23, and a converter neutral point resistor 24 connected to the C wiring 41 for suppressing dc resonance.

The inverter unit 3 includes: an inverter power conversion unit 31; an inverter P-side smoothing capacitor 32 connected between a positive potential level and a neutral point potential level to suppress potential variation between these potentials; an inverter N-side smoothing capacitor 33 connected between the neutral point potential level and the negative potential level to suppress potential variation between these potentials; an inverter P-side direct-current voltage detector 35 for measuring an inter-terminal voltage of the inverter P-side smoothing capacitor 32; an inverter N-side direct-current voltage detector 36 for measuring an inter-terminal voltage of the inverter N-side smoothing capacitor 33; and an inverter neutral point resistor 34 connected to the C wiring 41 for suppressing dc resonance.

The converter control device 5 controls the converter power conversion unit 21 so that the converted dc power has a desired value. The configuration of the converter control device 5 will be described later.

The inverter control device 6 controls the inverter power conversion unit 31 so that the output torque and the speed of the motor 4 satisfy desired characteristics. The configuration of the inverter control device 6 will be described later.

The power conversion device 100 further includes: a current detector 7 that detects and outputs an output current of the converter unit 2; a speed detector 8 directly connected to the motor 4, for detecting and outputting a speed of the motor 4; and a current detector 9 that detects and outputs the output current of the inverter unit 3.

A signal (output signal) of a detection value detected by the current detector 7 is input to the converter control device 5. Further, signals (output signals) of detection values detected by the

dc voltage detectors

25 and 26 are input to the converter control device 5. The converter control device 5 performs various arithmetic processes based on the input detection values, and outputs a signal for controlling the converter power conversion unit 21.

A signal (output signal) of a detection value detected by the speed detector 8 and a signal (output signal) of a detection value detected by the current detector 9 are input to the inverter control device 6. The inverter control device 6 performs various arithmetic processes based on the input detection values, and outputs a signal for controlling the inverter power conversion unit 31.

The converter control device 5 includes a dc voltage command generator 51, a dc voltage controller 52, a current controller 53, and a pulse generator 54.

The dc voltage command generator 51 outputs a dc voltage command value, which is a command value of the dc voltage to be output to the converter unit 2, to the dc voltage controller 52.

The dc voltage controller 52 calculates a converter output 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 value to the current controller 53. Specifically, the dc voltage controller 52 calculates the converter output current command value so that the total value of the detected values of the dc voltages input from the dc voltage detector 25 and the dc voltage detector 26 matches the dc voltage command value.

Neutral point voltage controller 55 calculates a voltage command for making the neutral point voltage zero based on the difference between the detected values of the dc voltages input from

dc voltage detectors

25 and 26, respectively, and outputs the voltage command to current controller 53.

The current controller 53 calculates a converter voltage command value so that the converter output current detection value output from the current detector 7 matches the converter output current command value input from the dc voltage controller 52, and outputs the converter voltage command value to the pulse generator 54. At this time, the current controller 53 calculates a converter 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/off control of each switching element of the converter power conversion unit 21 so that the output voltage of the converter power conversion unit 21 matches the converter output voltage command value input from the current controller 53, and outputs the pulse signal to the converter power conversion unit 21.

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, which is a command value of a speed for operating the motor 4, to the speed controller 62.

The speed controller 62 calculates a torque current command value of the motor so that the speed detection value input from the speed detector 8 matches the speed command value input from the speed command generator 61, and outputs the torque current command value of the motor to the current controller 63. Here, a value obtained by combining the torque current command value of the electric motor and a field current command value of the electric motor, which will be described later, is referred to as an inverter output current command value.

The neutral point voltage controller 65 calculates a voltage command for making the neutral point voltage zero based on the difference between the detected values of the dc voltages input from the dc voltage detector 35 and the dc voltage detector 36, respectively, and outputs the voltage command to the current controller 63.

The current controller 63 calculates an inverter voltage command value so that the inverter output current detection value input from the current detector 9 matches the inverter output current command value, and outputs the inverter voltage command value to the pulse generator 64. At this time, the current controller 63 calculates an inverter voltage command value in consideration of the voltage command input from the neutral point voltage controller 65.

The pulse generator 64 generates a pulse signal for on/off control of each switching element of the inverter power conversion unit 31 so that the output voltage of the inverter power conversion unit 31 matches the inverter output voltage command value input from the current controller 63, and outputs the pulse signal to the inverter power conversion unit 31.

Next, a configuration for realizing correction control for improving the control accuracy of the motor 4 in the power conversion device 100 will be described.

The inverter control device 6 of the power conversion device 100 further includes an excitation current command generator 66, a flux controller 67, a correction controller 68, an adder 69, and a 3-level motor voltage calculator 70.

When the motor to be controlled is, for example, an induction motor, the control device controls the excitation current so that the magnetic flux of the induction motor has a predetermined value. In order to effectively utilize the control region of the induction motor, control is used in which the magnetic flux is variable according to the speed. To achieve this, the field current command generator 66 outputs a reference field current command value for making the magnetic flux of the motor 4 a predetermined value to the flux controller 67. The flux controller 67 receives the speed detection value output from the speed detector 8, and calculates and outputs an excitation current command value that varies the reference excitation current command value based on the speed detection value.

Here, before the correction control is described, the influence of the magnetic flux saturation of the motor will be described. As shown in equation (1), the magnetic flux Φ of the motor is the product of the field inductance M and the field current Im of the motor.

Φ＝M×Im…(1)

Fig. 2 is a diagram showing the characteristics of magnetic flux saturation of the motor.

In the magnetic flux controller 67, when control is performed to reduce the field current in inverse proportion to the speed from a certain speed (referred to as "base speed") to the maximum speed (referred to as "maximum speed"), the speed electromotive force (= speed × magnetic flux) of the motor can be set to a fixed value from the base speed to the maximum speed. Fig. 3 is a diagram showing a relationship between speed, excitation current, and speed electromotive force.

However, as shown in fig. 2, when there is magnetic flux saturation, the magnetic field inductance M increases as the magnetic flux decreases. That is, M _ Top > M _ Base. Therefore, in the control for reducing the field current in inverse proportion to the speed, the magnetic flux and the speed electromotive force may become larger than assumed. If the influence of the increase in the speed electromotive force exceeds the output voltage of the power conversion device, the control may become impossible.

Therefore, correction control is performed to suppress an increase in speed electromotive force due to the influence of magnetic flux saturation of the motor.

Fig. 4 is a diagram showing a configuration of a conventional power conversion device for comparison with the power conversion device of the present embodiment. In fig. 4, the same components as those of the power conversion device according to the first embodiment shown in fig. 1 are denoted by the same reference numerals. The power conversion device 101 shown in fig. 4 includes an ac line voltage detector 10 and a filter circuit 11, and inputs an ac line voltage detection value output from the ac line voltage detector 10 to the calibration controller 68 via the filter circuit 11. When the ac line voltage detection value is larger than assumed, the correction controller 68 calculates and outputs a correction value for reducing the excitation current.

The adder 69 adds the correction value from the correction controller 68 to the excitation current command value output from the flux controller 67. Specifically, when there is magnetic flux saturation as shown in fig. 2, the speed electromotive force increases when the magnetic flux controller 67 outputs an excitation current command value inversely proportional to the speed. Therefore, the correction controller 68 outputs a negative correction value that further reduces the excitation current so that the actual speed electromotive force becomes a predetermined value. By adding the negative correction value to the excitation current command value by the adder 69, the excitation current Im becomes an excitation current (Im _ Top) smaller than the inverse proportional value as shown in the middle of fig. 3, and as a result, the speed electromotive force becomes constant.

By performing the correction control in this way, an increase in the speed electromotive force of the motor can be suppressed. However, in the conventional method using the ac line-to-line voltage detector 10 shown in fig. 4, the detection accuracy is poor because the detected voltage value is a rectangular wave. When a filter circuit having a large time constant is inserted to reduce the ripple of the rectangular wave, there is a problem that the accuracy of correction control is lowered due to delay. In addition, malfunction may occur due to an abnormality of the ac line voltage detector 10.

The power conversion apparatus 100 of the present embodiment takes the following measures against these problems.

The 3-level motor voltage calculator 70 according to embodiment 1 will be specifically described.

In fig. 1, the inverter voltage command values (ac phase voltage command values Vuref, vvref, vwref) output from the current controller 63, a positive side dc voltage detection value EpFB output from the dc voltage detector 35, and a negative side dc voltage detection value EnFB output from the dc voltage detector 36 are input to the 3-level motor voltage arithmetic unit 70. The 3-level motor voltage calculator 70 calculates estimated values (Vuvh, vvwh) of the ac line voltage of the motor 4 using these input signals. The estimated value of the ac line voltage of the motor 4 is input to the correction controller 68.

Next, the 3-level motor voltage calculator 70 according to embodiment 1 will be described in more detail.

The 3-level motor voltage calculator 70 includes a 3-level bipolar modulation voltage calculator 71, a 3-level unipolar modulation voltage calculator 72, a correction calculation selection unit 73, and an ac line-to-line voltage calculator 74.

The 3-level motor voltage operator 70 calculates a motor voltage from the ac phase voltage command values (Vuref, vvref, vwref) and the dc voltage detection values (EpFB, enFB). However, 3-level inverters include inverters based on bipolar modulation used at low voltage and inverters based on unipolar modulation used at high voltage, and the methods for calculating the motor voltage are different between the respective modulation systems. Therefore, the correction calculation selecting unit 73 selects and outputs the motor ac phase voltage estimated value of either the bipolar or unipolar based on the signal indicating whether the motor is bipolar or unipolar. The signal indicating whether it is bipolar or unipolar is, for example, a voltage command value. The voltage command value may be determined to be unipolar when it is larger than a certain set value, and may be bipolar when it is smaller than a certain set value.

Then, the ac line voltage calculator 74 calculates and outputs the motor ac line voltage estimated values (Vuvh, vvwh) based on the motor ac phase voltage estimated values (Vuh, vvh, vwh) selected by the correction calculation selection unit 73.

Next, the operation methods of the motor ac phase voltage estimated value will be described for bipolar modulation and unipolar modulation, respectively.

< method of operation in Bipolar modulation >

First, the calculation of the motor ac phase voltage drive value in the 3-level bipolar modulation will be described.

The power conversion device converts the magnitude of the voltage command into a pulse width, and performs on/off control of each switching element of the power conversion unit, thereby outputting a voltage in accordance with the command as an average voltage. In the case of bipolar modulation, a pulse signal is generated such that the difference between the area of the positive side voltage and the area of the negative side voltage matches the command. For example, when a zero voltage is output, the average voltage is set to zero by setting the positive side and the negative side to the same pulse width.

Here, if the positive side dc voltage Ep and the negative side dc voltage En are the same, that is, if the positive side and the negative side are balanced, the voltage becomes zero. However, if the positive side dc voltage Ep is different from the negative side dc voltage En, that is, if the positive side and the negative side are unbalanced, the voltage will not become zero. Therefore, when estimating the actual ac phase voltage of the motor, it is necessary to take into account the amount of variation due to the dc voltage. However, since the output voltage is determined by the difference between the Ep side and the En side in the bipolar modulation, the ratio of Ep or En is reflected in the voltage command, and thus the ac phase voltage of the motor cannot be estimated. Therefore, in the present embodiment, the estimation operation is performed by adding the correction amount to the original voltage command as described below. That is, the correction amount Δ Vh is calculated by equation (2).

ΔVh＝Vdb×α×ΔEp-Vdb×(1-α)×ΔEn…(2)

Where Vdb is a reference for bipolar operation of the voltage command, and α represents the pulse width on the Ep side, and is calculated by equation (3).

α = (ac voltage command% + 50%)/100% \8230: (3)

For example, when a voltage command of 50% or less is expressed by bipolar modulation, vdb is 50% voltage, the pulse width on the Ep side is α calculated by equation (3), and the pulse width on the En side is 1- α, whereby 50% voltage x (75/100) — 50% voltage x (1-75/100) =25% voltage can be obtained when the voltage command is 25%. The correction amount is calculated by taking the amounts of change in Ep and En into account. Δ Ep is the fluctuation amount of Ep, and is calculated by equation (4). Δ En is the variation of En and is calculated by equation (5).

ΔEp＝EpFB/Eb﹣1…(4)

ΔEn＝EnFB/Eb﹣1…(5)

Here, epFB is a P-side dc voltage detection value detected and output by the dc voltage detector 35. EnFB is an N-side dc voltage detection value detected and output by the dc voltage detector 36. Eb represents a reference value of the dc voltage. When there is no variation from the reference value, Δ Ep and Δ En are zero.

For example, if it is assumed that there is a fluctuation of 1.1 times on the Ep side and a fluctuation of 0.9 times on the En side, the output voltage at the time of a voltage command of 0% is 50% voltage × (50/100) × 1.1-50% voltage × (1-50/100) × 0.9=5% voltage. Further, according to equation (2), the correction amount Δ Vh =50% voltage × (50/100) × 0.1-50% voltage × (1-50/100) × (-0.1) =5%. By adding correction amount Δ Vh =5% to voltage command 0%, an estimated value of the motor ac phase voltage can be obtained.

Fig. 7 is a diagram for explaining the 3-level bipolar modulation voltage operator 71.

The 3-level bipolar modulation voltage calculator 71 receives the ac phase voltage command values (Vuref, vvref, vwref) and the dc voltage detection values (EpFB, enFB), calculates α of each phase by the Ep-side pulse width calculator 711 according to equation (3), and outputs α u, α v, and α w. Dc voltage variation amount arithmetic unit 712 calculates and outputs Δ Ep and Δ En from EpFB and EnFB in accordance with expressions (4) and (5). Δ Ep, Δ En, and α u, α v, α w are input to the correction amount operator 713.

The correction amount calculator 713 calculates and outputs the correction amounts Δ Vhu, Δ Vhv, and Δ Vhw for the respective phases according to equation (2). The correction amounts Δ Vhu, Δ Vhv, Δ Vhw are input to the bipolar motor phase voltage operator 714 together with the ac phase voltage command value. The bipolar motor phase voltage operator 714 adds a correction amount to the ac phase voltage command of each phase to calculate and output motor ac phase voltage drive values Vuh _ d, vvh _ d, vwh _ d at the time of bipolar modulation.

< method of operation in case of unipolar modulation >

Next, the calculation of the motor ac phase voltage drive value in the 3-level unipolar modulation will be described.

In the case of unipolar modulation, unlike the case of bipolar modulation, a pulse signal is generated so that areas that vary in accordance with the pulse width on the positive side and the negative side coincide with a command. For example, when a 50% voltage is output, the positive side has a 50% pulse width, and the average voltage is 50%.

At this time, when the dc voltage Ep on the positive side fluctuates from the reference, the output does not become a 50% voltage. Therefore, when estimating the actual ac phase voltage of the motor, it is necessary to take into account the amount of variation due to the dc voltage. In the case of unipolar modulation, the rate of change in Ep may be reflected in the voltage command. Similarly, the negative side can be calculated by reflecting the variation ratio of En in the voltage command. Therefore, in the present embodiment, as shown in equations (6) and (7), the estimated value of the ac phase voltage is calculated by multiplying the original voltage command by the variation ratio.

Vhp = ac voltage command% × Epk (ac voltage command is positive) \ 8230; (6)

Vhn = ac voltage command% × Enk (when ac voltage command is negative) \ 8230; (7)

Here, epk is a variation ratio of the P-side direct-current voltage detection value, and is calculated by equation (8). Enk is a variation ratio of the N-side direct-current voltage detection value, and is calculated by equation (9).

Epk＝EpFB/Eb…(8)

Enk＝EnFB/Eb…(9)

Here, epFB is a P-side dc voltage detection value detected and output by the dc voltage detector 35. EnFB is an N-side dc voltage detection value detected and output by the dc voltage detector 36. Eb represents a reference value of the dc voltage. When the dc voltage does not vary from the reference value, epk and Enk are 1.

Fig. 9 is a diagram for explaining the 3-level unipolar modulation voltage arithmetic unit 72.

The 3-level unipolar modulation voltage calculator 72 receives the ac phase voltage command values (Vuref, vvref, vwref) and the dc voltage detection values (EpFB, enFB), and calculates and outputs the variation ratios Epk, enk by the dc voltage variation ratio calculator 721 in accordance with equations (8) and (9). Epk, enk and Vuref, vvref, vwref are input to phase voltage operator 722. Phase voltage operator 722 calculates Vhp and Vhn according to expressions (6) and (7), respectively, and outputs the calculated values. The Vhp, vhn of each phase are input to the unipolar motor phase voltage operator 723 together with the ac phase voltage command value. The unipolar motor phase voltage operator 723 outputs Vhp when the polarity of the ac voltage command value is positive, and outputs Vhn when the polarity of the ac voltage command value is negative. In this way, the motor ac phase voltage drive values Vuh _ u, vvh _ u, vwh _ u in the case of unipolar modulation are generated.

As described above, in embodiment 1, in the 3-level power converter, the correction control is performed by switching the operation method between bipolar modulation and unipolar modulation in consideration of the fluctuation of the dc voltage in the ac phase voltage command and calculating the motor ac line voltage estimated values (Vuvh, vvwh) from the motor ac phase voltage pushed values (Vuh, vvh, vwh). Thus, compared to the case of using a conventional ac line-to-line voltage detector for a motor, highly accurate correction control can be performed without being affected by a ripple component and a filter delay due to a rectangular wave. Further, since the ac line-to-line voltage detector is not used, the risk of malfunction of the correction control due to an abnormality of the ac line-to-line voltage detector and planned stoppage is eliminated.

[ example 2]

In embodiment 2, a power conversion device using a 2-level converter is exemplified.

Fig. 10 is an overall configuration diagram of a power converter of embodiment 2. In the power converter 102 of the present embodiment shown in fig. 10, the same components as those of the power converter 100 of embodiment 1 shown in fig. 1 are denoted by the same reference numerals. The power conversion device 102 of embodiment 2 is different from the power conversion device 100 shown in fig. 1 in that there is no portion relating to the neutral point that is a feature of the 3-level converter, for example, there are no converter neutral point resistors 24 and 34, neutral point voltage controllers 55 and 65, and the dc voltage detector 37 detects Vdc between the P side and the N side.

Here, the description will be mainly given of the portions of embodiment 2 different from embodiment 1.

In the power conversion device 102 of embodiment 2, the inverter control device 6 includes a speed command generator 61, a speed controller 62, a current controller 63, a pulse generator 64, an excitation current command generator 66, a flux controller 67, a correction controller 68, an adder 69, and a 2-level motor voltage calculator 80. The speed command generator 61, speed controller 62, current controller 63, pulse generator 64, field current command generator 66, flux controller 67, correction controller 68, and adder 69 are basically the same as in embodiment 1.

Here, the 2-level motor voltage arithmetic unit 80 will be specifically described.

As shown in fig. 10, the inverter voltage reference values (ac phase voltage reference values Vuref, vvref, vwref) output from the current controller 63 and the positive side dc voltage detection value VdcFB output from the dc voltage detector 37 are input to the 2-level motor voltage operator 80. The 2-level motor voltage calculator 80 calculates and outputs estimated values (Vuvh, vvwh) of the ac line voltage of the motor using these input signals. The estimated value of the ac line voltage of the motor is input to the correction controller 68.

Next, the 2-level motor voltage calculator 80 according to embodiment 2 will be described in more detail.

Fig. 11 is a diagram for explaining the 2-level motor voltage arithmetic unit 80. The method of calculating the motor voltage differs between the 3-level inverter and the 2-level inverter. The 2-level motor voltage calculator 80 includes a 2-level modulation voltage calculator 81 and an ac line voltage calculator 82. In the 2-level motor voltage arithmetic unit 80, motor ac phase voltage drive values (Vuh, vvh, vwh) and motor ac line voltage estimated values (Vuvh, vvwh) are calculated and output from the ac phase voltage command values (Vuref, vvref, vwref) and the dc voltage detection value (Vdc FB).

Next, the calculation of the motor ac phase voltage drive value in embodiment 2 will be described.

Fig. 12 is a diagram for explaining a relationship between a voltage command and a rectangular wave voltage to be output in the case of 2 levels.

In the case of 2 levels, unlike the case of 3 levels, a pulse signal is generated in such a manner that the area of one pulse on the positive side and the negative side coincides with the command. For example, when a 100% voltage is output as the voltage command, a pulse signal having a pulse width of 100% on the P side is generated. When 0% voltage is output, a pulse signal having a pulse width of 50% on the P side and 50% on the N side is generated. When a voltage of-100% is output, a pulse signal having a pulse width of 100% on the N-side is generated.

Here, if the dc voltage Vdc between the P side and the N side varies from the reference, the voltage command does not match the actual output voltage. Therefore, in order to estimate and calculate the actual ac phase voltage of the motor, it is necessary to consider the amount of variation due to the dc voltage. In the 2-level ac voltage command, the variation ratio of the dc voltage Vdc is reflected, whereby the ac phase voltage estimated value of the motor can be calculated. Therefore, in the present embodiment, as shown in equation (10), the ac phase voltage is estimated by multiplying the original voltage command by the variation ratio.

Vh = AC voltage command% × Vdck \8230; (10)

Where Vdck is a fluctuation ratio of the dc voltage detection value, and is calculated by equation (11).

Vdck＝VdcFB/Vdcb…(11)

Where VdcFB is a direct-current voltage detection value between the P side and the N side detected and output by the direct-current voltage detector 37. Vdcb represents a reference value of the direct-current voltage. When the dc voltage does not vary from the reference value, vdck is 1.

The 2-level modulation voltage operator 81 is input with ac phase voltage reference values (Vuref, vvref, vwref) and a dc voltage detection value (Vdc FB). The dc voltage fluctuation ratio calculator 811 calculates and outputs Vdck from VdcFB according to equation (11). Vdck and Vuref, vvref, vwref are input to phase voltage operator 812. Phase voltage operator 812 calculates and outputs motor ac phase voltage drive values Vuh, vvh, vwh according to equation (10).

As described above, in embodiment 2, in the 2-level converter, the fluctuation of the dc voltage is taken into account in the ac phase voltage command, the estimated motor ac line voltage values (Vuvh, vvh) are calculated from the motor ac phase voltage pushed values (Vuh, vvh, vwh), and the correction control is performed using the calculated values. Thus, compared to the case of using a conventional ac line voltage detector for a motor, correction control can be performed with high accuracy without being affected by a ripple component and a filter delay due to a rectangular wave. Further, since the ac line-to-line voltage detector is not used, it is possible to eliminate the risk of malfunction of the correction control due to an abnormality of the ac line-to-line voltage detector or an unplanned stop.

In the correction control of the present embodiment, the variation in the speed electromotive force due to the change in the excitation inductance caused by the saturation of the magnetic flux is controlled to a predetermined value by correcting the excitation current based on the motor voltage estimated value of the present embodiment. In addition to this, it is also possible to appropriately control a slip control error caused by a change in the resistance of the motor 2 times by correcting the slip amount based on the motor voltage estimated value in the present embodiment.

[ example 3]

In example 3, a power conversion device having a self-test function of diagnosing an abnormality of an ac line-to-line voltage detector is exemplified in a configuration including the ac line-to-line voltage detector and using a detected value thereof for correction control.

In the power converter 103 of the present embodiment shown in fig. 14, the same components as those of the power converter 100 of embodiment 1 shown in fig. 1 are denoted by the same reference numerals. The power conversion device 103 of embodiment 3 is different from the power conversion device 100 shown in fig. 1 in that it includes an ac line voltage detector 10 and a filter circuit 11, and an ac line voltage detector abnormality determiner 90 and a display 91 and the like are added.

Here, the description will be mainly given of the portions of embodiment 3 different from embodiment 1.

As described above, in the device including the ac line-to-line voltage detector, there is a possibility that an unintended stop may occur due to a malfunction of the correction control caused by an abnormality of the ac line-to-line voltage detector. Therefore, the power conversion device 103 according to embodiment 3 employs a configuration in which the abnormality of the ac line voltage detector is diagnosed using the motor voltage estimated value.

Next, the ac line voltage detector abnormality determiner 90 according to embodiment 3 will be specifically described.

As shown in fig. 14, the inverter control device 6 includes a speed command generator 61, a speed controller 62, a current controller 63, a pulse generator 64, a neutral point voltage controller 65, an excitation current command generator 66, a flux controller 67, a correction controller 68, an adder 69, a 3-level motor voltage calculator 70, an ac line voltage detector abnormality determiner 90, and a display 91. The speed command generator 61, speed controller 62, current controller 63, pulse generator 64, neutral point voltage controller 65, field current command generator 66, flux controller 67, correction controller 68, adder 69, and 3-level motor voltage arithmetic unit 70 are basically the same as those in embodiment 1.

Here, the ac line voltage detector abnormality determiner 90 will be specifically described.

As shown in fig. 14, ac line voltage detection values (VuvFB, vvwFB) are input from the ac line voltage detector 10 to the ac line voltage detector abnormality determiner 90 via the filter circuit 11, and estimated ac line voltages (Vuvh, vvwh) of the motor are input from the 3-level motor voltage calculator 70. The ac line voltage detector abnormality determiner 90 performs abnormality diagnosis of the ac line voltage detector based on these input signals.

Generally, if the power converter is not stopped, the output of the alternating-current line-to-line voltage detector is not zero. When there is some abnormality such as disconnection or slack in the ac line voltage detection circuit, only the output of the ac line voltage detector is zero.

In the abnormality diagnosis 201 shown in fig. 15, when the output of any one of the ac line-to-line voltage detectors is zero in step 202, it is determined that the ac line-to-line voltage detection circuit in the corresponding portion is abnormal, that is, the wiring connected to the ac line-to-line voltage detector is abnormal in step 203, and it indicates that there is an abnormality in the ac line-to-line voltage detection circuit. At this time, if the output of the ac line-to-line voltage detector is a value sufficiently close to zero, it can be determined that the output of the ac line-to-line voltage detector is substantially zero. Therefore, if the output of the ac line voltage detector is equal to or less than a predetermined threshold value, it is determined that the ac line voltage detection circuit at that location is abnormal.

If the output of any of the ac line-to-line voltage detectors is not zero in step 202, the ac line-to-line voltage estimated value Vuvh between the UV is set as a reference and the ac line-to-line voltage detected value VuvFB between the UV is compared with the reference in step 204. If there is a deviation of a predetermined threshold value or more between the UV ac line-to-line voltage detection value VuvFB and the reference, it is determined that there is an abnormality in the ac line-to-line voltage detector, and in step 205, a display is made indicating that there is an abnormality in the Vuv ac line-to-line voltage detector.

If there is no difference of a predetermined threshold value or more between the ac line-to-line voltage detection value VuvFB between the UVs and the ac line-to-line voltage estimated value Vuvh between the UVs in step 204, the ac line-to-line voltage detection value VvwFB between the VWs is compared with a reference vvwhh between the VWs in step 206. If there is a deviation of a predetermined threshold value or more between the alternating-current line-to-line voltage detection value VvwFB between VW and the reference, it is determined that there is an abnormality in the alternating-current line-to-line voltage detector, and at step 207, an indication that there is an abnormality in the alternating-current line-to-line voltage detector indicating Vvw is displayed.

If any of

steps

203, 205, and 207 indicates an abnormality, a message prompting the inspection and replacement of the abnormal portion is displayed in step 208 of fig. 15, and the series of operations is terminated.

As described above, in the power conversion apparatus including the ac line-to-line voltage detector, the ac line-to-line voltage estimated value is compared as a reference to detect an abnormality of the ac line-to-line voltage detector, and inspection and replacement of the ac line-to-line voltage detector, which is recommended to be defective, are displayed, thereby enabling efficient maintenance.

[ example 4]

In example 4, a power converter having a function of continuing operation when an abnormality occurs in an ac line-to-line voltage detector is exemplified as a configuration including the ac line-to-line voltage detector and using a detected value thereof for correction control. When an abnormality occurs in the ac line voltage detector, the operation is continued using the substitute signal instead of the detection value, which is referred to as a follow-up operation.

Fig. 16 is an overall configuration diagram of the power converter according to embodiment 4.

Note that, in the power conversion device 104 of embodiment 4 shown in fig. 16, the same components as those of the power conversion device 103 of embodiment 3 shown in fig. 14 are denoted by the same reference numerals. The power conversion device 104 according to embodiment 4 is different from the power conversion device 103 according to embodiment 3 in that an abnormality calculation value switch 92 is additionally provided.

Here, the description will be given mainly of the portions of embodiment 4 different from embodiment 3.

The ac line voltage detector 10 inputs the detected ac line voltage values (Vuv FB, vvwFB) to the abnormality calculation value switch 92 via the filter circuit 11, and also inputs abnormality determination information indicating whether or not the estimated ac line voltage values (Vuvh, vvwh) of the motor output from the ac line voltage detector abnormality determiner 90 are abnormal. If the abnormality determination information does not include information indicating that there is an abnormality in the ac line-to-line voltage detection value of the motor, the abnormality-time operation value switch 92 outputs the detection value of the ac line-to-line voltage detector 10 to the correction controller 68. However, when the abnormality determination information indicates that there is an abnormality in the ac line-to-line voltage detection value of the motor, the abnormality-time operation value switch 92 outputs the substitute signal to the correction controller 68 instead of the detection value of the ac line-to-line voltage detector 10 having the abnormality.

Next, the abnormal time operation value switching device 92 of embodiment 4 will be specifically described.

Fig. 17 is a diagram for explaining the abnormal operation value switcher 92.

In fig. 17, the ac line voltage detection values VuvFB and VvwFB are input to the abnormality time calculated value switch 92, and the ac line voltage estimated values (Vuvh and Vvwh) and signals (Vuv FB abnormality determination signal and VvwFB abnormality determination signal) indicating whether or not the detection value of the ac line voltage detector 10 is abnormal are input from the ac line voltage detector abnormality determiner 90. The VuvFB abnormality determination signal is a signal indicating whether or not the ac line voltage detection value VuvFB is abnormal. The VvwFB abnormality determination signal is a signal indicating whether or not the ac line voltage detection value VvwFB is abnormal.

If VuvFB is abnormal, the abnormal time operation value switch 92 outputs the motor ac line voltage estimated value Vuvh as Vuvout to the correction controller 68 instead of VuvFB. In addition, if VvwFB is abnormal, the abnormal-time operation value switch 92 outputs the motor ac line voltage estimated value Vvwh instead of VvwFB to the correction controller 68 as Vvwout. In the correction controller 68, the correction amount is calculated based on Vuvout and Vvwout.

As described above, in the present embodiment, in the same manner as in embodiment 3, in the power conversion apparatus including the ac line-to-line voltage detector, the ac line-to-line voltage estimated value is compared as a reference to determine an abnormality of the ac line-to-line voltage detector, and an inspection and replacement display of the ac line-to-line voltage detector that recommends a failure is performed, so that maintenance can be performed efficiently.

Further, in the present embodiment, when it is determined that there is an abnormality in the ac line-to-line voltage detector, the operation can be continued by replacing the abnormal ac line-to-line voltage detection value with the corresponding ac line-to-line voltage estimated value in parallel with the display of the inspection and replacement of the ac line-to-line voltage detector recommended to have an abnormality, and the risk of unplanned stoppage of the system including the power converter can be reduced. For example, by continuing the operation of the system by coping with the operation until the next periodic inspection, it is possible to quickly replace the ac line voltage detector for the specified abnormality in the periodic inspection.

In embodiment 3 and embodiment 4, the description has been given as an example using a 3-level converter, but the present invention is not limited to this. The same can be applied even in the case of using a 2-level converter.

The above-described embodiments include the following matters. However, the matters contained in the above-described embodiments are not limited to the matters described below.

(item 1)

A power conversion device is provided with:

a converter that converts an alternating current input into a plurality of potentials;

an inverter that converts the voltages of the plurality of potentials into an alternating current output to a motor;

a smoothing capacitor connected between 2 of the plurality of potentials and configured to suppress potential variation between the potentials;

a dc voltage detector that detects a potential difference between the potentials to which the smoothing capacitor is connected as a dc voltage detection value;

a current detector that detects an output current of the inverter and outputs the detected output current as an inverter output current;

an inverter output current controller that generates an inverter output voltage command for the inverter so that the inverter output current coincides with an inverter output current command;

a motor voltage calculator that calculates a motor voltage estimated value that is an estimated value of an ac line voltage of the motor, based on the inverter output voltage command and the dc voltage detected value;

a correction control unit that calculates a correction value for correcting a signal for controlling the motor based on the estimated motor voltage value;

and an adder that adds the correction value to a control command signal to generate the inverter output current command.

Thus, the estimated value of the ac line voltage of the motor is calculated from the inverter output voltage command and the dc voltage detection value, and the correction value for correcting the signal for controlling the motor is calculated from the estimated value.

(item 2)

According to the power conversion device described in item 1,

the power conversion apparatus is capable of switching a plurality of modulation schemes,

the motor voltage calculator calculates the motor voltage estimated value by a calculation method corresponding to a modulation method of the power conversion device.

This makes it possible to realize a power conversion device capable of switching between a plurality of modulation schemes depending on the application.

(item 3)

According to the power conversion device described in item 2,

the power conversion device is a 3-level power conversion device,

the plurality of modulation schemes include a bipolar modulation scheme,

the motor voltage calculator includes:

a pulse width calculator that calculates pulse widths on the positive side and the negative side from the inverter output voltage command;

a dc voltage fluctuation amount calculator that calculates a fluctuation amount of the dc voltage detection value with respect to a predetermined reference voltage;

a correction amount calculator that calculates a correction amount using the pulse width and the variation amount,

when the bipolar modulation method is used, the power conversion device calculates the correction amount using the pulse width calculator, the dc voltage variation calculator, and the correction amount calculator, and calculates the motor voltage estimation value by correcting the inverter output voltage command by the correction amount.

Thus, when the 3-level bipolar modulation method is used, the motor can be controlled with high accuracy.

(item 4)

According to the power conversion device described in item 2,

the power conversion device is a 3-level power conversion device,

the plurality of modulation schemes comprise a unipolar modulation scheme,

the motor voltage calculator includes:

a dc voltage fluctuation ratio calculator that calculates a fluctuation ratio of the dc voltage detection value with respect to a predetermined reference voltage;

a phase voltage calculator that calculates an estimated value of an alternating-current phase voltage in a case where the alternating-current voltage command is positive and a case where the alternating-current voltage command is negative, based on the alternating-current voltage command that is the inverter output voltage command and the variation ratio,

in the case of using the unipolar modulation method, the power conversion device calculates the ac phase voltage estimated value by the dc voltage fluctuation ratio calculator and the phase voltage calculator, and outputs the ac phase voltage estimated value corresponding to the polarity of the ac voltage command, thereby generating the motor voltage estimated value.

Thus, when the 3-level unipolar modulation system is used, the motor can be controlled with high accuracy.

(item 5)

According to the power conversion device described in item 1,

the power conversion device is a 2-level power conversion device,

the motor voltage calculator includes: a DC voltage fluctuation ratio calculator for calculating a fluctuation ratio of the DC voltage detection value to a predetermined reference voltage,

the power conversion device calculates the variation ratio by the dc voltage variation ratio calculator, and calculates the motor voltage estimated value from an ac voltage command that is the inverter output voltage command and the variation ratio.

Thus, the 2-level modulation system can control the motor with high accuracy.

(item 6)

A power conversion device is provided with:

a smoothing capacitor connected between 2 of the plurality of potentials for suppressing potential variation between the potentials;

an ac line voltage detector that detects an output voltage of the inverter and outputs the detected voltage as a motor voltage value;

a correction control unit that calculates a correction value for correcting a signal for controlling the motor based on the motor voltage detection value;

an adder that adds the correction value to a control command signal to generate an inverter output current command;

a current detector that detects an output current of the inverter and outputs the output current as an inverter output current;

an inverter output current controller that generates an inverter output voltage command for the inverter so that the inverter output current coincides with the inverter output current command;

a motor voltage calculation unit that calculates a motor voltage estimated value that is an estimated value of an ac line voltage of the motor, based on the inverter output voltage command and the dc voltage detection value;

and an abnormality determiner for determining an abnormality of the ac line-to-line voltage detector based on the estimated motor voltage value.

In this way, the estimated value of the ac line-to-line voltage of the motor is calculated from the inverter output voltage command and the dc voltage detection value, and the abnormality of the ac line-to-line voltage detector is determined based on the estimated value.

(item 7)

According to the power conversion device described in item 6,

the ac line voltage detector abnormality determiner determines that there is an abnormality in a wire connected to an ac line voltage detector having an output equal to or less than a predetermined threshold value.

Thus, in the configuration using the ac line-to-line voltage detector, it is possible to detect an abnormality of the wiring connected to the ac line-to-line voltage detector.

(item 8)

The power conversion device according to item 6,

the power conversion device further includes: and an abnormality time calculation value switcher configured to input the motor voltage estimation value calculated by the motor voltage calculation unit to the correction control unit, instead of the motor voltage detection value from the ac line voltage detector determined to be abnormal, when the ac line voltage detector abnormality determiner determines that the ac line voltage detector is abnormal.

In this way, since the abnormality of the ac line-to-line voltage detector is determined and the motor voltage estimated value calculated by the motor voltage calculation unit is switched to based on the motor voltage detected value from the ac line-to-line voltage detector having an abnormality, in the configuration using the ac line-to-line voltage detector, the control of the motor can be normally continued even if the ac line-to-line voltage detector has an abnormality.

(item 9)

The power conversion device according to any one of items 6 to 8,

the abnormality determiner of the ac line-to-line voltage detector causes a display to display information relating to the abnormality when it is determined that the ac line-to-line voltage detector is abnormal.

Thus, when an abnormality of the ac line-to-line voltage detector is determined, information relating to the abnormality is displayed, and therefore, in a configuration using the ac line-to-line voltage detector, the abnormality of the ac line-to-line voltage detector can be easily detected.

(item 10)

A motor control method for a power conversion device, the power conversion device including:

an inverter that converts the voltages at the plurality of potentials into an alternating current output to the motor;

a DC voltage detector for detecting a potential difference between the potentials to which the smoothing capacitor is connected as a DC voltage detection value,

wherein an output current of the inverter is detected as an inverter output current;

generating an inverter output voltage command for the inverter such that the inverter output current coincides with an inverter output current command;

calculating a motor voltage estimated value, which is an estimated value of an ac line voltage of the motor, based on the inverter output voltage command and the dc voltage detection value;

calculating a correction value for correcting a signal for controlling the motor based on the motor voltage estimation value;

and adding the correction value and a control command signal to generate the inverter output current command.

(item 11)

An abnormality detection method for detecting an abnormality in a power conversion device, the power conversion device comprising:

an alternating-current line voltage detector that detects an output voltage of the inverter and outputs the detected voltage as a motor voltage detected value,

wherein the content of the first and second substances,

calculating a correction value for correcting a signal for controlling the motor based on the motor voltage detection value;

adding the correction value and a control command signal to generate an inverter output current command;

detecting an output current of the inverter as an inverter output current;

generating an inverter output voltage command for the inverter such that the inverter output current coincides with the inverter output current command;

and determining abnormality of the alternating-current line voltage detector based on the motor voltage estimated value.

Claims

1. A power conversion device is characterized by comprising:

a motor voltage calculator that calculates a motor voltage estimated value that is an estimated value of an ac line voltage of the motor, based on the inverter output voltage command and the dc voltage detection value;

2. The power conversion apparatus according to claim 1,

3. The power conversion apparatus according to claim 2,

the power conversion device is a 3-level power conversion device,

the plurality of modulation schemes include a bipolar modulation scheme,

the motor voltage calculator includes:

a correction amount calculator that calculates a correction amount using the pulse width and the fluctuation amount,

4. The power conversion apparatus according to claim 2,

the power conversion device is a 3-level power conversion device,

the plurality of modulation modes include a unipolar modulation mode,

the motor voltage calculator includes:

when the unipolar modulation method is used, the power conversion device calculates the ac phase voltage estimated value by the dc voltage fluctuation ratio calculator and the phase voltage calculator, and outputs the ac phase voltage estimated value corresponding to the polarity of the ac voltage command, thereby generating the motor voltage estimated value.

5. The power conversion apparatus according to claim 1,

the power conversion device is a 2-level power conversion device,

the motor voltage calculator includes: a DC voltage fluctuation ratio calculator for calculating a fluctuation ratio of the DC voltage detection value with respect to a predetermined reference voltage,

the power conversion device calculates the variation ratio by the dc voltage variation ratio calculator, and calculates the motor voltage estimated value from the ac voltage command that is the inverter output voltage command and the variation ratio.

6. A power conversion device is characterized by comprising:

a dc voltage detector that detects a potential difference between potentials at which the smoothing capacitor is connected as a dc voltage detection value;

an ac line voltage detector that detects an output voltage of the inverter and outputs the detected output voltage as a motor voltage detection value;

7. The power conversion apparatus according to claim 6,

8. The power conversion apparatus according to claim 6,

the power conversion device further includes: and an abnormality time calculated value switching unit that, when the ac line voltage detector abnormality determiner determines that the ac line voltage detector is abnormal, inputs the motor voltage estimated value calculated by the motor voltage calculating unit to the correction control unit in place of the motor voltage detected value from the ac line voltage detector determined to be abnormal.

9. The power conversion apparatus according to any one of claims 6 to 8,

10. A motor control method for a power conversion device, the power conversion device including:

a DC voltage detector for detecting a potential difference between potentials at which the smoothing capacitor is connected as a DC voltage detection value,

it is characterized in that the preparation method is characterized in that,

detecting an output current of the inverter as an inverter output current;

11. An abnormality detection method for detecting an abnormality in a power conversion device, the power conversion device comprising:

it is characterized in that the preparation method is characterized in that,

detecting an output current of the inverter as an inverter output current;

generating an inverter output voltage command for the inverter so that the inverter output current coincides with the inverter output current command;

and determining abnormality of the ac line voltage detector based on the estimated motor voltage value.