Power conversion device and motor control method

Abstract

The present application provides a technique for correcting control with high accuracy without using an AC line-to-line voltage detector. A power conversion device has a converter, an inverter that converts voltages of a plurality of potentials into an AC output to a motor, a DC voltage detector that detects a potential difference between two potentials of the plurality of potentials as a DC voltage detection value, a current detector that outputs an output current of the inverter as an inverter output current, an inverter output current controller that generates an inverter output voltage command to the inverter so that the inverter output current coincides with an inverter output current command, a motor voltage calculator that calculates a motor voltage estimation value, which is an estimation value of an AC line-to-line voltage of the motor, from 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 from 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.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a power conversion device provided with an inverter that drives a motor. BACKGROUND

[0002] As a power converter that drives a motor, a power conversion device is known that converts power of an alternating current power source into power of a variable frequency at a variable voltage. The main circuit of the power conversion device is configured to be provided with a converter that converts alternating current into direct current, a direct current circuit connected to the converter, and an inverter connected to the converter via the direct current circuit that converts direct current into alternating current, and is provided with a smoothing capacitor in the direct current circuit. The power conversion device uses the inverter to make the magnitude and frequency of the alternating voltage applied to the motor variable, thereby controlling the speed and torque of the motor.

[0003] As a control system of a motor, a speed control system and a current control system are used. The speed control system detects the speed of the motor by a speed detector, and feeds back the detected value of the speed detector. The current control system detects the current flowing through the motor by a current detector, and feeds back the detected value of the current detector. In addition, there is a method of applying correction to the command value in order to improve the control accuracy of the motor (Patent Documents 1 and 2).

[0004] There is a method of detecting the line-to-line voltage of the motor by a line-to-line voltage detector, and using the detected value for control. 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 degradation in accuracy due to a deviation between the design value and the actual value of the resistance, mutual inductance, and the like of the motor, and a change in characteristics. Therefore, there is a correction control that extracts a deviation amount between the design value and the actual value from the detected value of the line-to-line voltage of the motor, and adds a correction amount to the slip amount and the excitation current in such a way that the deviation amount is zero.

[0005] PRIOR ART DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-208397

[0007] Patent Document 2: Japanese Patent Application Publication No. H09-149658 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] In the above-described method of applying correction to control using the detected value of the line-to-line voltage, the line-to-line voltage detector detects the output voltage from the semiconductor element in the power converter. The output voltage is a rectangular wave accompanied by switching, and contains a large ripple component in the detected value, and due to this ripple component, there is a possibility that the accuracy will be degraded.

[0010] In addition, in a case where a configuration is adopted in which a filter circuit having a large time constant is used to detect the output of the filter circuit in order to reduce the large ripple component, the detection of the output voltage is delayed, and it is possible that precision is degraded due to the delay.

[0011] In addition, in a configuration using an AC line-to-line voltage detector, the AC line-to-line voltage detector generates an abnormality, the precision of the correction control is degraded, and worst of all, an unscheduled stop can occur.

[0012] An object of the present application is to provide a technique capable of performing correction control with high precision without using an AC line-to-line voltage detector.

[0013] Another object of the present application is to provide a technique capable of detecting an abnormality of an AC line-to-line voltage detector in a configuration using an AC line-to-line voltage detector.

[0014] Method for solving technical problem

[0015] A power conversion device of one embodiment of the present application includes a converter that converts an AC input into a plurality of potentials, an inverter that converts voltages of the plurality of potentials into an AC output to a motor, a smoothing capacitor that is connected between two potentials of the plurality of potentials and that suppresses a 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 of the inverter as an inverter output current, an inverter output current controller that generates an inverter output voltage command to the inverter in such a manner that the inverter output current coincides with an inverter output current command, a motor voltage calculator that calculates an estimated value of an AC line-to-line voltage of the motor, i.e., a motor voltage estimated value, from the inverter output voltage command and the DC voltage detection value, a correction control unit that calculates a correction value that corrects a signal for controlling the motor from the motor voltage estimated value, and an adder that adds the correction value to a control command signal to generate the inverter output current command.

[0016] The power conversion device of another aspect of the present application includes: a converter that converts an alternating current input into a plurality of potentials; an inverter that converts voltages of the plurality of potentials into an alternating current output to a motor; a smoothing capacitor connected between two of the plurality of potentials for suppressing a potential variation between the potentials; a direct current voltage detector that detects a potential difference between the potentials to which the smoothing capacitor is connected as a direct current voltage detection value; an alternating current line-to-line voltage detector that detects an output voltage of the inverter and outputs the same as a motor voltage detection value; a correction control section that calculates a correction value for correcting a signal for controlling the motor based on the motor voltage detection value; a summer 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 same as an inverter output current; an inverter output current controller that generates an inverter output voltage command for the inverter in such a manner that the inverter output current coincides with the inverter output current command; a motor voltage calculation section that calculates an estimated value of an alternating current line-to-line voltage of the motor, that is, a motor voltage estimated value, based on the inverter output voltage command and the direct current voltage detection value; and an alternating current line-to-line voltage detector abnormality determiner that determines an abnormality of the alternating current line-to-line voltage detector based on the motor voltage estimated value.

[0017] Effects of the Invention

[0018] According to one aspect of the present disclosure, an estimated value of an alternating current line-to-line voltage of a motor is calculated based on an inverter output voltage command and a direct current voltage detection value, and a correction value for correcting a signal for controlling the motor is calculated based on the estimated value, so that high-precision correction control can be performed without using an alternating current line-to-line voltage detector.

[0019] According to another aspect of the present disclosure, an estimated value of an alternating current line-to-line voltage of a motor is calculated based on an inverter output voltage command and a direct current voltage detection value, and an abnormality of an alternating current line-to-line voltage detector is determined based on the estimated value, so that the abnormality of the alternating current line-to-line voltage detector can be detected in a configuration using the alternating current line-to-line voltage detector. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a whole configuration view of the power conversion device of Embodiment 1.

[0021] Figure 2 is a graph showing a magnetic flux saturation characteristic of a motor.

[0022] Figure 3 is a graph showing a relationship among a speed, an excitation current, and a speed electromotive force.

[0023] Figure 4is a diagram showing the structure of an existing power conversion device for comparison with the power conversion device of the present embodiment.

[0024] Figure 5 is a diagram for explaining the structure of the 3-level motor voltage calculator 70.

[0025] Figure 6 is a diagram showing the relationship between the voltage command and the output rectangular wave voltage at the time of bipolar.

[0026] Figure 7 is a diagram for explaining the 3-level bipolar modulation voltage calculator 71.

[0027] Figure 8 is a diagram showing the relationship between the voltage command and the output rectangular wave voltage at the time of unipolar modulation.

[0028] Figure 9 is a diagram for explaining the 3-level unipolar modulation voltage calculator 72.

[0029] Figure 10 is a diagram showing the overall structure of the power conversion device of Embodiment 2.

[0030] Figure 11 is a diagram for explaining the 2-level motor voltage calculator 80.

[0031] Figure 12 is a diagram showing the relationship between the voltage command and the output rectangular wave voltage at the time of 2-level.

[0032] Figure 13 is a diagram for explaining the 2-level modulation voltage calculator 81.

[0033] Figure 14 is a diagram showing the overall structure of the power conversion device of Embodiment 3.

[0034] Figure 15 is a flowchart of abnormality diagnosis of the AC line-to-line voltage detector.

[0035] Figure 16 is a diagram showing the overall structure of the power conversion device of Embodiment 4.

[0036] Figure 17 is a diagram for explaining the abnormality-time calculation value switcher 92.

[0037] Explanation of Reference Numerals

[0038] 1 AC power source, 2 converter unit, 3 inverter unit, 4 motor, 5 converter control device, 6 inverter control device, 7 current detector, 8 speed detector, 9 current detector, 10 AC line-to-line voltage detector, 11 filter circuit, 21 converter power conversion section, 22 converter P-side smoothing capacitor, 23 converter N-side smoothing capacitor, 24 converter neutral point resistor, 25 converter P-side DC voltage detector, 26 converter N-side DC voltage detector, 31 inverter power conversion section, 32 inverter P-side smoothing capacitor, 33 inverter N-side smoothing capacitor, 34 inverter neutral point resistor, 35 inverter P-side DC voltage detector, 36 inverter N-side DC voltage detector, 37 DC voltage detector, 40 P wiring, 41 C wiring, 42 N wiring, 51 DC voltage command generator, 52 DC voltage controller, 53 current controller, 54 pulse generator, 55 neutral point voltage controller, 61 speed command generator, 62 speed controller, 63 current controller, 64 pulse generator, 65 neutral point voltage controller, 66 field current command generator, 67 flux controller, 68 correction controller, 69 adder, 70 3-level motor voltage calculator, 71 3-level bipolar modulation voltage calculator, 72 3-level unipolar modulation voltage calculator, 73 correction calculation selection section, 74 AC line-to-line voltage calculator, 80 2-level motor voltage calculator, 81 2-level modulation voltage calculator, 82 AC line-to-line voltage calculator, 90 AC line-to-line voltage detector abnormality determiner, 91 display, 92 abnormality-time calculation value switcher, 100 power conversion device, 101 power conversion device, 102 power conversion device, 103 power conversion device, 104 power conversion device, 711 Ep-side pulse width calculator, 712 DC voltage variation amount calculator, 713 correction amount calculator, 714 bipolar motor phase voltage calculator, 721 DC voltage variation ratio calculator, 722 phase voltage calculator, 723 unipolar motor phase voltage calculator, 811 DC voltage variation ratio calculator, 812 phase voltage calculator. DETAILED DESCRIPTION

[0039] Several embodiments are described with reference to the drawings. Furthermore, the embodiments described below are not intended to define the essential characteristics of the invention, and not all of the elements described in the embodiments and combinations thereof are necessarily essential to the solution of the invention.

[0040] [Embodiment 1]

[0041] In Embodiment 1, a power conversion device using a 3-level converter is exemplified.

[0042] Figure 1 FIG. 1 is a diagram showing the overall configuration of a power conversion device according to an embodiment of the present application.

[0043] The power conversion device 100 is a device that converts the alternating-current electric power from the alternating-current power source 1 to drive the motor 4. The power conversion device 100 is provided with: a converter unit (also referred to as a converter) 2 that converts the alternating-current electric power from the alternating-current power source 1 to direct-current electric power; an inverter unit (also referred to as an inverter) 3 that converts the direct-current electric power output from the converter unit 2 to the desired alternating-current electric 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.

[0044] The converter unit 2 is a so-called 3-level converter that converts the alternating-current electric power to direct-current electric power of a positive potential (first potential) level, a neutral point (zero) potential (second potential) level, and a negative potential (third potential) level. The inverter unit 3 is a so-called 3-level inverter that converts the direct-current electric power of the positive potential (first potential) level, the neutral point (zero) potential (second potential) level, and the negative potential (third potential) level to the alternating-current electric power for the motor 4. Between the converter unit 2 and the inverter unit 3, the positive potential level is connected by a P line 40, the neutral point potential level is connected by a C line 41, and the negative potential level is connected by an N line 42.

[0045] The converter unit 2 is provided with a converter electric power conversion section 21, a converter P-side smoothing capacitor 22 and a converter N-side smoothing capacitor 23 for suppressing variation in direct-current voltage, a converter P-side direct-current voltage detector 25 for measuring the voltage between the terminals of the converter P-side smoothing capacitor 22, a converter N-side direct-current 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 that is connected to the C line 41 and is for suppressing direct-current resonance.

[0046] The inverter unit 3 is provided with: an inverter electric power conversion section 31; an inverter P-side smoothing capacitor 32 that is connected between the positive potential level and the neutral point potential level, and suppresses variation in potential between these potentials; an inverter N-side smoothing capacitor 33 that is connected between the neutral point potential level and the negative potential level, and suppresses variation in potential between these potentials; an inverter P-side direct-current voltage detector 35 for measuring the voltage between the terminals of the inverter P-side smoothing capacitor 32; an inverter N-side direct-current voltage detector 36 for measuring the voltage between the terminals of the inverter N-side smoothing capacitor 33; and an inverter neutral point resistor 34 that is connected to the C line 41, and is for suppressing direct-current resonance.

[0047] The converter control device 5 controls the converter power conversion section 21 so that the converted direct-current electric power becomes a desired value. The structure of the converter control device 5 is described later.

[0048] The inverter control device 6 controls the inverter power conversion section 31 so that the output torque and speed of the motor 4 satisfy a desired characteristic. The structure of the inverter control device 6 is described later.

[0049] 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 that is directly coupled to the motor 4 and detects and outputs a speed of the motor 4, and a current detector 9 that detects and outputs an output current of the inverter unit 3.

[0050] A signal (output signal) of a detection value detected by the current detector 7 is input to the converter control device 5. In addition, signals (output signals) of detection values detected by the direct-current voltage detectors 25 and 26 are also input to the converter control device 5. The converter control device 5 performs various arithmetic processes based on these input detection values, and outputs a signal that controls the converter power conversion section 21.

[0051] 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 these input detection values, and outputs a signal that controls the inverter power conversion section 31.

[0052] The converter control device 5 includes a direct-current voltage command generator 51, a direct-current voltage controller 52, a current controller 53, and a pulse generator 54.

[0053] The direct-current voltage command generator 51 outputs a command value of a direct-current voltage to be output to the converter unit 2, that is, a direct-current voltage command value, to the direct-current voltage controller 52.

[0054] The direct-current voltage controller 52 calculates a converter output current command value based on the direct-current voltage command value input from the direct-current voltage command generator 51 and detection values of direct-current voltages input from the direct-current voltage detectors 25 and 26, and outputs to the current controller 53. Specifically, the direct-current voltage controller 52 calculates the converter output current command value so that the sum of the detection values of the direct-current voltages input from the direct-current voltage detector 25 and the direct-current voltage detector 26 respectively coincides with the direct-current voltage command value.

[0055] The neutral point voltage controller 55 calculates a voltage command that makes the neutral point voltage zero based on the difference between the detection values of the direct-current voltages input from the direct-current voltage detectors 25 and 26 respectively, and outputs to the current controller 53.

[0056] The current controller 53 calculates a converter voltage command value in such a manner that the converter output current detection value output from the current detector 7 coincides with the converter output current command value input from the direct-current voltage controller 52, and outputs the converter voltage command value to the pulse generator 54. At this time, the current controller 53 calculates the converter voltage command value taking into account the voltage command input from the neutral point voltage controller 55.

[0057] The pulse generator 54 calculates a pulse signal for on / off control of each switching element of the converter power conversion section 21 in such a manner that the output voltage of the converter power conversion section 21 coincides with the converter output voltage command value input from the current controller 53, and outputs the pulse signal to the converter power conversion section 21.

[0058] The inverter control device 6 is provided with a speed command generator 61, a speed controller 62, a current controller 63, a pulse generator 64, and a neutral point voltage controller 65.

[0059] The speed command generator 61 outputs a command value of a speed at which the motor 4 is to be operated, i.e., a speed command value, to the speed controller 62.

[0060] The speed controller 62 calculates a torque current command value of the motor in such a manner that the speed detection value input from the speed detector 8 coincides with 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 motor and a field current command value of the motor described later is referred to as an inverter output current command value.

[0061] The neutral point voltage controller 65 calculates a voltage command for making the neutral point voltage zero based on a difference between the detection values of the direct-current voltages input from the direct-current voltage detector 35 and the direct-current voltage detector 36, and outputs the voltage command to the current controller 63.

[0062] The current controller 63 calculates an inverter voltage command value in such a manner that the inverter output current detection value input from the current detector 9 coincides with 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 the inverter voltage command value taking into account the voltage command input from the neutral point voltage controller 65.

[0063] The pulse generator 64 generates a pulse signal for on / off control of each switching element of the inverter power conversion section 31 in such a manner that the output voltage of the inverter power conversion section 31 coincides with the inverter output voltage command value input from the current controller 63, and outputs the pulse signal to the inverter power conversion section 31.

[0064] Next, a structure for implementing correction control for improving the control accuracy for the motor 4 in the power conversion device 100 will be described.

[0065] 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.

[0066] In the case where the control target motor is an induction motor, for example, the control device controls the excitation current so that the flux of the induction motor becomes a predetermined value. In addition, in order to effectively utilize the control region of the induction motor, control that makes the flux variable depending on the speed is used. In order to achieve this, the excitation current command generator 66 outputs a reference excitation current command value for making the flux of the motor 4 a predetermined value to the flux controller 67. The flux controller 67 calculates and outputs an excitation current command value that makes the reference excitation current command value variable depending on the speed detection value, taking the speed detection value output from the speed detector 8 as input.

[0067] Here, before the correction control is described, the influence of the saturation of the flux of the motor will be described. As shown in Expression (1), the flux Φ of the motor becomes the product of the excitation inductance M of the motor and the excitation current Im.

[0068] Φ = M x Im... (1)

[0069] Figure 2 is a graph showing the characteristics of the saturation of the flux of the motor.

[0070] In the flux controller 67, if control is performed to reduce the excitation current in inverse proportion to the speed from a certain speed (which will be referred to as the "base speed") to the highest speed (which will be referred to as the "top speed"), it is possible to make the speed electromotive force (= speed x flux) of the motor a fixed value from the base speed to the top speed. Figure 3 is a graph showing the relationship between the speed, the excitation current, and the speed electromotive force.

[0071] However, as shown in Figure 2 , in the case where the flux is saturated, if the flux becomes small, the excitation inductance M becomes large. That is, M_Top > M_Base. Therefore, in control to reduce the excitation current in inverse proportion to the speed, there is a possibility that the flux and the speed electromotive force become larger than expected. Moreover, in the case where the influence of this increase in the speed electromotive force exceeds the output voltage of the power conversion device, it can become impossible to control.

[0072] Therefore, correction control is performed in order to suppress the increase in the speed electromotive force caused by the influence of the saturation of the flux of the motor.

[0073] Figure 4is a diagram showing a configuration of a conventional power conversion device for comparison with the power conversion device of the present embodiment. Further, in Figure 4 the first embodiment shown in Figure 1 the same structures as those of the power conversion device related to the first embodiment shown in Figure 4 The power conversion device 101 of the first embodiment has an AC line-to-line voltage detector 10 and a filter circuit 11, and inputs an AC line-to-line voltage detection value output from the AC line-to-line voltage detector 10 to a correction controller 68 via the filter circuit 11. In a case where the AC line-to-line voltage detection value is larger than expected, the correction controller 68 calculates and outputs a correction value for reducing the field current.

[0074] The adder 69 adds the correction value from the correction controller 68 to the field current command value output from the flux controller 67. Specifically, in a case where there is flux saturation as in Figure 2 If the flux controller 67 outputs a field current command value that is inversely proportional to the speed, the speed electromotive force becomes large. Therefore, the correction controller 68 outputs a negative correction value that further reduces the field current, so that the actual speed electromotive force becomes a predetermined value. By adding the negative correction value to the field current command value by the adder 69, the field current Im becomes a field current (Im_Top) that is smaller than the inverse proportional value, as shown in the middle of Figure 3 As a result, the speed electromotive force becomes constant.

[0075] By performing the correction control like this, it is possible to suppress an increase in the speed electromotive force of the motor. However, in the conventional method using the AC line-to-line voltage detector 10 shown in Figure 4 Since the detection voltage value is a rectangular wave, the detection accuracy is poor. When a filter circuit having a large time constant is inserted in order to reduce the ripple of the rectangular wave, there is a problem that the accuracy of the correction control decreases due to the delay. In addition, it is also possible that a malfunction occurs due to an abnormality of the AC line-to-line voltage detector 10.

[0076] The power conversion device 100 of the present embodiment implements the following countermeasures against these problems.

[0077] The 3-level motor voltage calculator 70 related to Embodiment 1 will be described in detail.

[0078] In Figure 1In the 3-level motor voltage calculator 70, the inverter voltage command values (the AC phase voltage command values Vuref, Vvref, Vwref) output from the current controller 63, the positive-side DC voltage detection value EpFB output from the DC voltage detector 35, and the negative-side DC voltage detection value EnFB output from the DC voltage detector 36 are input. The 3-level motor voltage calculator 70 calculates the AC line-to-line voltage estimation values (Vuvh, Vvwh) of the motor 4 using these input signals. The AC line-to-line voltage estimation values of the motor 4 are input to the correction controller 68.

[0079] Next, the 3-level motor voltage calculator 70 related to Embodiment 1 is described in more detail.

[0080] Figure 5 is a diagram for explaining the structure of the 3-level motor voltage calculator 70.

[0081] 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 operation selection section 73, and an AC line-to-line voltage calculator 74.

[0082] The 3-level motor voltage calculator 70 calculates the motor voltage from the AC phase voltage command values (Vuref, Vvref, Vwref) and the DC voltage detection values (EpFB, EnFB). However, in the 3-level inverter, there are an inverter based on bipolar modulation used at low voltage and an inverter based on unipolar modulation used at high voltage, and the operation method of the motor voltage differs between the respective modulation methods. Therefore, the correction operation selection section 73 selects the motor AC phase voltage estimation value of either the bipolar or the unipolar according to a signal indicating whether it is bipolar or unipolar. The signal indicating whether it is bipolar or unipolar is, for example, the voltage command value. It is sufficient that the unipolar is determined in the case where the voltage command value is greater than a certain set value and the bipolar is determined in the case where it is less than the certain set value.

[0083] Then, in the AC line-to-line voltage calculator 74, the motor AC line-to-line voltage estimation values (Vuvh, Vvwh) are calculated and output from the motor AC phase voltage estimation values (Vuh, Vvh, Vwh) selected by the correction operation selection section 73.

[0084] Next, the operation method of the motor AC phase voltage estimation value is described for the bipolar modulation and the unipolar modulation, respectively.

[0085] <Operation method in the case of bipolar modulation>

[0086] First, the operation of the motor AC phase voltage estimation value in the 3-level bipolar modulation is described.

[0087] Figure 6 is a graph showing the relationship between the voltage command at the time of bipolar and the output rectangular wave voltage.

[0088] The power conversion device converts the magnitude of the voltage command into the pulse width, and performs on / off control of each switching element of the power conversion section, thereby outputting the voltage in accordance with the command as an average voltage. In the case of bipolar modulation, the pulse signal is generated so that the difference between the area of the voltage on the positive side and the area of the voltage on the negative side is in accordance with the command. For example, in the case of outputting zero voltage, by setting the positive side and the negative side to the same pulse width, the average voltage is set to zero.

[0089] Here, if the direct current voltage Ep on the positive side and the direct current voltage En on the negative side are the same, that is, if the positive side and the negative side are balanced, it becomes zero voltage. However, if the direct current voltage Ep on the positive side and the direct current voltage En on the negative side are different, that is, if the positive side and the negative side are in an unbalanced state, it does not become zero voltage. Therefore, when performing the estimation operation on the alternating current phase voltage of the actual motor, it is necessary to take into account the amount of variation caused by the direct current voltage. However, since the output voltage is determined by the difference between the Ep side and the En side at the time of bipolar modulation, by reflecting the ratio of Ep or En in the voltage command, it is not possible to perform the estimation operation on the alternating current phase voltage of the motor. Therefore, in the present embodiment, as described below, the estimation operation is performed by adding a correction amount to the original voltage command. That is, the correction amount ΔVh is calculated by formula (2).

[0090] ΔVh = Vdb x α x ΔEp - Vdb x (1 - α) x ΔEn... (2)

[0091] where Vdb is the reference at the time of bipolar of the voltage command, and α represents the pulse width on the Ep side, and is calculated by formula (3).

[0092] α = (alternating current voltage command % + 50 %) / 100 %... (3)

[0093] For example, in the case of expressing a voltage command of 50 % or less by bipolar modulation, Vdb is set to 50 % voltage, the pulse width on the Ep side is set to α calculated by formula (3), and the pulse width on the En side is set to 1 - α, whereby when the voltage command is 25 %, it becomes 50 % voltage x (75 / 100) - 50 % voltage x (1 - 75 / 100) = 25 % voltage. The correction amount is calculated by taking into account the amount of variation of Ep and En. ΔEp is the amount of variation of Ep, and is calculated by formula (4). ΔEn is the amount of variation of En, and is calculated by formula (5).

[0094] ΔEp = EpFB / Eb - 1... (4)

[0095] ΔEn = EnFB / Eb - 1... (5)

[0096] Here, EpFB is the P-side DC voltage detection value detected by the DC voltage detector 35 and output. EnFB is the N-side DC voltage detection value detected by the DC voltage detector 36 and output. Eb denotes a reference value of the DC voltage. In the case where there is no variation from the reference value, ΔEp, ΔEn are zero.

[0097] For example, if a case where there is a variation of 1.1 times on the Ep side and a variation of 0.9 times on the En side is assumed, the output voltage at the voltage command of 0% is 50% voltage x (50 / 100) x 1.1 - 50% voltage x (1 - 50 / 100) x 0.9 = 5% voltage. Further, according to equation (2), the correction amount ΔVh = 50% voltage x (50 / 100) x 0.1 - 50% voltage x (1 - 50 / 100) x (-0.1) = 5%. By adding the correction amount ΔVh = 5% to the voltage command of 0%, the estimated value of the motor AC phase voltage can be obtained.

[0098] Figure 7 is a diagram for explaining the 3-level bipolar modulation voltage calculator 71.

[0099] The 3-level bipolar modulation voltage calculator 71 takes the AC phase voltage command values (Vuref, Vvref, Vwref) and the DC voltage detection values (EpFB, EnFB) as inputs, and calculates αu, αv, αw of each phase as α according to equation (3) by the Ep-side pulse width calculator 711. The DC voltage variation amount calculator 712 calculates ΔEp and ΔEn according to equations (4), (5) from EpFB and EnFB and outputs them. ΔEp, ΔEn and αu, αv, αw are input to the correction amount calculator 713.

[0100] The correction amount calculator 713 calculates the correction amounts ΔVhu, ΔVhv, ΔVhw of each phase according to equation (2) and outputs them. The correction amounts ΔVhu, ΔVhv, ΔVhw are input to the bipolar motor phase voltage calculator 714 together with the AC phase voltage command values. The bipolar motor phase voltage calculator 714 calculates and outputs the motor AC phase voltage command values Vuh_d, Vvh_d, Vwh_d at the time of bipolar modulation by adding the correction amounts to the AC phase voltage commands of each phase.

[0101] <Operation method in the case of unipolar modulation>

[0102] Next, the operation of the motor AC phase voltage command values at the time of 3-level unipolar modulation will be explained.

[0103] Figure 8 is a diagram for explaining the relationship between the voltage command and the rectangular wave voltage output at the time of unipolar modulation.

[0104] In the case of unipolar modulation, unlike in the case of bipolar modulation, the pulse signal is generated in such a manner that the areas that vary on the positive side and the negative side according to the pulse width are in agreement with the command. For example, in the case of outputting 50% voltage, the positive side becomes 50% pulse width, so that the average voltage becomes 50%.

[0105] At this time, when the direct current voltage Ep on the positive side varies with respect to the reference, the output does not become 50% voltage. Therefore, when performing the estimation operation on the alternating phase voltage of the actual motor, the amount of variation caused by the direct current voltage needs to be taken into consideration. In the case of unipolar modulation, it is sufficient to reflect the variation ratio of Ep in the voltage command. In addition, the negative side can also be operated in the same manner 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 alternating phase voltage is calculated by multiplying the original voltage command by the variation ratio.

[0106] Vhp = alternating voltage command % x Epk (when the alternating voltage command is positive)... (6)

[0107] Vhn = alternating voltage command % x Enk (when the alternating voltage command is negative)... (7)

[0108] wherein Epk is the variation ratio of the P-side direct current voltage detection value, which is calculated by equation (8). Enk is the variation ratio of the N-side direct current voltage detection value, which is calculated by equation (9).

[0109] Epk = EpFB / Eb... (8)

[0110] Enk = EnFB / Eb... (9)

[0111] In addition, here, EpFB is the P-side direct current voltage detection value detected and output by the direct current voltage detector 35. EnFB is the N-side direct current voltage detection value detected and output by the direct current voltage detector 36. Eb indicates the reference value of the direct current voltage. In the case where the direct current voltage does not vary from the reference value, Epk and Enk are 1.

[0112] Figure 9 is a diagram for explaining the 3-level unipolar modulation voltage operator 72.

[0113] 3-level unipolar modulation voltage calculator 72 inputs the AC phase voltage command values (Vuref, Vvref, Vwref) and the DC voltage detection values (EpFB, EnFB) as inputs, calculates the variation ratios Epk, Enk by the DC voltage variation ratio calculator 721 according to the equations (8), (9), and outputs them. The Epk, Enk and the Vuref, Vvref, Vwref are input to the phase voltage calculator 722. The phase voltage calculator 722 calculates Vhp, Vhn according to the equations (6), (7), respectively, and outputs them. The Vhp, Vhn of each phase are input to the unipolar motor phase voltage calculator 723 together with the AC phase voltage command values. The unipolar motor phase voltage calculator 723 outputs Vhp when the polarity of the AC voltage command value is positive, and outputs Vhn when it is negative. In this way, the motor AC phase voltage push values Vuh_u, Vvh_u, Vwh_u in the case of unipolar modulation are generated.

[0114] As described above, in Embodiment 1, in the 3-level power converter, the variation of the DC voltage is taken into account in the AC phase voltage command, the operation mode is switched between the bipolar modulation and the unipolar modulation, and the motor AC line-to-line voltage estimation values (Vuvh, Vvwh) are calculated from the motor AC phase voltage push values (Vuh, Vvh, Vwh), whereby the correction control is performed. Thereby, compared with the case where the existing motor AC line-to-line voltage detector is used, high-precision correction control that is not affected by the ripple component caused by the rectangular wave, the filter delay, and the like can be performed. In addition, since the AC line-to-line voltage detector is not used, the risk of erroneous operation of the correction control, unscheduled stop, and the like caused by abnormality of the AC line-to-line voltage detector is eliminated.

[0115] [Embodiment 2]

[0116] In Embodiment 2, a power conversion device using a 2-level converter is exemplified.

[0117] Figure 10 is a whole configuration view of the power conversion device of Embodiment 2. In Figure 10 The power conversion device 102 of the present embodiment shown in Figure 1 The same structures as those of the power conversion device 100 related to Embodiment 1 shown in Figure 1 The power conversion device 102 of Embodiment 2 differs from the power conversion device 100 of

[0118] Here, mainly the parts different from Embodiment 1 in Embodiment 2 are described.

[0119] In the power conversion device 102 of Embodiment 2, the inverter control device 6 is provided with 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, the speed controller 62, the current controller 63, the pulse generator 64, the excitation current command generator 66, the flux controller 67, the correction controller 68, and the adder 69 are substantially the same as those of Embodiment 1.

[0120] Here, the 2-level motor voltage calculator 80 is described in detail.

[0121] As shown in FIG. 8, the inverter voltage command values (the AC phase voltage command 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 calculator 80. The 2-level motor voltage calculator 80 uses these input signals to calculate the motor AC line-to-line voltage estimation values (Vuvh, Vvwh) and outputs them. The motor AC line-to-line voltage estimation values are input to the correction controller 68. Figure 10

[0122] Next, the 2-level motor voltage calculator 80 related to Embodiment 2 is described in more detail.

[0123] Figure 11 is a diagram for explaining the 2-level motor voltage calculator 80. In a 3-level inverter and a 2-level inverter, the method of calculating the motor voltage is different. The 2-level motor voltage calculator 80 is provided with a 2-level modulation voltage calculator 81 and an AC line-to-line voltage calculator 82. In the 2-level motor voltage calculator 80, the motor AC phase voltage estimation values (Vuh, Vvh, Vwh) and the motor AC line-to-line voltage estimation values (Vuvh, Vvwh) are calculated and output based on the AC phase voltage command values (Vuref, Vvref, Vwref) and the DC voltage detection values (VdcFB).

[0124] Next, the calculation of the motor AC phase voltage estimation values in Embodiment 2 is described.

[0125] Figure 12 is a diagram for explaining the relationship between the voltage command and the output rectangular wave voltage in the 2-level case.

[0126] ​In the case of 2-level, unlike the case of 3-level, the pulse signal is generated in such a manner that the area of one pulse of the positive side and the negative side coincides with the command. As the voltage command, for example, in the case of outputting 100% voltage, a pulse signal is generated in which the pulse width of the P side is 100%. In the case of outputting 0% voltage, a pulse signal is generated in which the pulse width of the P side is 50% and the pulse width of the N side is 50%. In the case of outputting -100% voltage, a pulse signal is generated in which the pulse width of the N side is 100%.

[0127] Here, if the direct current voltage Vdc between the P side and the N side varies with respect to the reference, the voltage command does not coincide with the actual output voltage. Therefore, in order to estimate the alternating current phase voltage of the actual motor, the amount of variation caused by the direct current voltage needs to be taken into account. In 2-level, by reflecting the variation ratio of the direct current voltage Vdc in the alternating current voltage command, the alternating current phase voltage estimation value of the motor can be calculated. Therefore, in the present embodiment, as in Expression (10), the alternating current phase voltage is estimated by multiplying the original voltage command by the variation ratio.

[0128] Vh = Alternating current voltage command % x Vdck... (10)

[0129] where Vdck is the variation ratio of the direct current voltage detection value, which is calculated by Expression (11).

[0130] Vdck = VdcFB / Vdcb... (11)

[0131] where VdcFB is the direct current voltage detection value between the P side and the N side, which is detected and output by the direct current voltage detector 37. Vdcb indicates the reference value of the direct current voltage. In the case where the direct current voltage does not vary with respect to the reference value, Vdck is 1.

[0132] Figure 13 is a diagram for explaining the 2-level modulation voltage calculator 81.

[0133] The alternating current phase voltage command values (Vuref, Vvref, Vwref) and the direct current voltage detection value (VdcFB) are input to the 2-level modulation voltage calculator 81. The direct current voltage variation ratio calculator 811 calculates and outputs Vdck from VdcFB according to Expression (11). Vdck and Vuref, Vvref, Vwref are input to the phase voltage calculator 812. The phase voltage calculator 812 calculates and outputs the motor alternating current phase voltage estimation values Vuh, Vvh, Vwh according to Expression (10).

[0134] As described above, in Embodiment 2, in the 2-level converter, the variation of DC voltage is considered in the AC phase voltage command, and the estimated values ​​of the AC line-to-line voltage of the motor (Vuvh, Vvwh) are calculated based on the AC phase voltage drive values ​​(Vuh, Vvh, Vwh), and used for correction control. Therefore, compared to using a conventional motor AC line-to-line voltage detector, it is not affected by ripple components caused by rectangular waves or filter delays, and correction control can be performed with high precision. Furthermore, since an AC line-to-line voltage detector is not used, the risk of malfunctions in correction control or unplanned shutdowns caused by abnormalities in the AC line-to-line voltage detector can be eliminated.

[0135] Furthermore, in the correction control of this embodiment, the excitation current is corrected based on the estimated motor voltage value of this embodiment, thereby controlling the fluctuation of the speed electromotive force caused by the change in excitation inductance due to magnetic flux saturation to a predetermined value. In addition, the slip amount can also be corrected based on the estimated motor voltage value of this embodiment, thereby appropriately controlling the slip control error caused by the change in the secondary resistance of the motor.

[0136] [Example 3]

[0137] In Example 3, a power conversion device with a self-testing function for diagnosing abnormalities of the AC line-to-line voltage detector is illustrated in a structure that includes an AC line-to-line voltage detector and uses its detected value for correction control.

[0138] Figure 14 This is an overall structural diagram of the power conversion device in Example 3.

[0139] exist Figure 14 In the power conversion device 103 of this embodiment shown, for the power conversion device 103 of this embodiment ... Figure 1 The power conversion device 100 of Embodiment 1 shown has the same structure and is labeled with the same reference numerals. The power conversion device 103 of Embodiment 3 is the same as... Figure 1 The difference in the power conversion device 100 shown is that it includes an AC line voltage detector 10 and a filter circuit 11, and also adds an AC line voltage detector anomaly detector 90 and a display 91.

[0140] Here, we will mainly describe the parts of Example 3 that differ from Example 1.

[0141] As described above, in devices equipped with AC line-to-line voltage detectors, malfunctions in the correction control caused by abnormalities in the AC line-to-line voltage detector can lead to unplanned shutdowns. Therefore, in the power conversion device 103 of Embodiment 3, a structure is adopted for diagnosing abnormalities in the AC line-to-line voltage detector using an estimated motor voltage value.

[0142] Next, the AC line voltage detector anomaly detector 90 involved in Embodiment 3 will be described in detail.

[0143] like Figure 14 As shown, 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 arithmetic unit 70, an AC line-to-line voltage detector anomaly detector 90, and a display 91. The speed command generator 61, speed controller 62, current controller 63, pulse generator 64, neutral point voltage controller 65, excitation 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 in Embodiment 1.

[0144] Here, we will specifically describe the AC line voltage detector anomaly detector 90.

[0145] like Figure 14 As shown, the AC line voltage detector 10 receives the detected AC line voltage values ​​(VuvFB, VvwFB) from the AC line voltage detector 10 via the filter circuit 11, and the estimated AC line voltage values ​​(Vuvh, Vvwh) of the motor are received from the 3-level motor voltage calculator 70. Based on these input signals, the AC line voltage detector anomaly detector 90 performs anomaly diagnosis on the AC line voltage detector.

[0146] Figure 15 This is a flowchart for diagnosing abnormalities in an AC line voltage detector.

[0147] Normally, if the power converter is not stopped, the output of the AC line-to-line voltage detector will not be zero. However, in the event of an anomaly such as a broken wire or slack in the AC line-to-line voltage detection circuit, only the output of the AC line-to-line voltage detector will be zero.

[0148] exist Figure 15 In the anomaly diagnosis 201 shown, in step 202, if the output of any AC line voltage detector is zero, in step 203, it is determined that there is an anomaly in the AC line voltage detection circuit of the corresponding location, that is, an anomaly in the wiring connected to the AC line voltage detector, indicating that there is an anomaly in the AC line voltage detection circuit. Furthermore, if the output of the AC line voltage detector is sufficiently close to zero, it can be determined that the output of the AC line voltage detector is substantially zero. Therefore, if the output of the AC line voltage detector is below a predetermined threshold, it is determined that there is an anomaly in the AC line voltage detection circuit of that location.

[0149] In the case where the output of either of the AC line-to-line voltage detectors is not zero in step 202, the AC line-to-line voltage detection value VuvFB between U and V is compared with the reference in step 204, with the AC line-to-line voltage estimation value Vuvh between U and V serving as the reference. In the case where there is a deviation of more than a predetermined threshold between the 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 a display indicating that the AC line-to-line voltage detector Vuv is abnormal is performed in step 205.

[0150] In the case where there is no deviation of more than a predetermined threshold between the AC line-to-line voltage detection value VuvFB and the AC line-to-line voltage estimation value Vuvh between U and V in step 204, the AC line-to-line voltage detection value VvwFB between V and W is compared with the reference in step 206, with the AC line-to-line voltage estimation value Vvwh between V and W serving as the reference. In the case where there is a deviation of more than a predetermined threshold between the AC line-to-line voltage detection value VvwFB and the reference, it is determined that there is an abnormality in the AC line-to-line voltage detector, and a display indicating that the AC line-to-line voltage detector Vvw is abnormal is performed in step 207.

[0151] In the case where a display indicating an abnormality is performed in any one of steps 203, 205, and 207, a message prompting an inspection and replacement of the abnormal site is displayed in step 208 of the series of operations, and the series of operations is ended. Figure 15

[0152] As described above, in the power conversion device having the AC line-to-line voltage detector, by comparing the AC line-to-line voltage estimation value as a reference, an abnormality in the AC line-to-line voltage detector is detected, and a display prompting an inspection and replacement of the AC line-to-line voltage detector having a defect is performed, so that maintenance can be performed efficiently.

[0153] [Embodiment 4]

[0154] In Embodiment 4, a power conversion device having a function of continuing operation when an abnormality occurs in the AC line-to-line voltage detector is exemplified in a structure provided with the AC line-to-line voltage detector and using a detection value thereof for correction control. A case where operation is continued using a substitute signal instead of the detection value when an abnormality occurs in the AC line-to-line voltage detector is referred to as a coping operation.

[0155] Figure 16 is a whole structure diagram of the power conversion device related to Embodiment 4.

[0156] Further, in Figure 16 the power conversion device 104 of Embodiment 4 shown in FIG. 10, the AC line-to-line voltage detection value VuvFB between U and V is compared with the reference in step 204, with the AC line-to-line voltage estimation value Vuvh between U and V serving as the reference. In the case where there is a deviation of more than a predetermined threshold between the 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 a display indicating that the AC line-to-line voltage detector Vuv is abnormal is performed in step 205. Figure 14 ​The same components of the power conversion device 103 of Embodiment 3 are denoted by the same reference numerals. The power conversion device 104 of Embodiment 4 differs from the power conversion device 103 of Embodiment 3 in that an abnormality-time operation value switcher 92 is additionally provided.

[0157] Here, the portion of Embodiment 4 that differs from Embodiment 3 will be mainly described.

[0158] The AC line-to-line voltage detection values (VuvFB, VvwFB) are input to the abnormality-time operation value switcher 92 from the AC line-to-line voltage detector 10 via the filter circuit 11, and at the same time, the abnormality determination information indicating whether the AC line-to-line voltage estimation values (Vuvh, Vvwh) of the motor are abnormal or not are input from the AC line-to-line voltage detector abnormality determiner 90. If there is no information indicating that the AC line-to-line voltage detection values of the motor are abnormal in the abnormality determination information, the abnormality-time operation value switcher 92 outputs the detection values of the AC line-to-line voltage detector 10 to the correction controller 68. However, when it is indicated in the abnormality determination information that the AC line-to-line voltage detection values of the motor are abnormal, the abnormality-time operation value switcher 92 outputs a substitute signal instead of the detection values of the AC line-to-line voltage detector 10 that are abnormal to the correction controller 68.

[0159] Next, the abnormality-time operation value switcher 92 of Embodiment 4 will be described in detail.

[0160] Figure 17 is a diagram for explaining the abnormality-time operation value switcher 92.

[0161] In Figure 17 , the AC line-to-line voltage detection values VuvFB, VvwFB are input to the abnormality-time operation value switcher 92, and the AC line-to-line voltage estimation values (Vuvh, Vvwh) and signals (VuvFB abnormality determination signal, VvwFB abnormality determination signal) indicating whether the detection values of the AC line-to-line voltage detector 10 are abnormal or not are input from the AC line-to-line voltage detector abnormality determiner 90. The VuvFB abnormality determination signal is a signal indicating whether the AC line-to-line voltage detection value VuvFB is abnormal or not. The VvwFB abnormality determination signal is a signal indicating whether the AC line-to-line voltage detection value VvwFB is abnormal or not.

[0162] If VuvFB is abnormal, the abnormality-time operation value switcher 92 outputs the motor AC line-to-line voltage estimation value Vuvh instead of VuvFB as Vuvout to the correction controller 68. In addition, if VvwFB is abnormal, the abnormality-time operation value switcher 92 outputs the motor AC line-to-line voltage estimation value Vvwh instead of VvwFB as Vvwout to the correction controller 68. In the correction controller 68, the correction amount is calculated based on Vuvout, Vvwout.

[0163] As explained above, in the present embodiment, as in Embodiment 3, in the power conversion device having the AC line-to-line voltage detector, the abnormality of the AC line-to-line voltage detector is judged by comparing the AC line-to-line voltage estimation value as a reference, the inspection and replacement of the AC line-to-line voltage detector in which the abnormality is recommended are performed, and the display is performed, so that the maintenance can be efficiently performed.

[0164] Further, in the present embodiment, in the case where it is judged that the abnormality exists in the AC line-to-line voltage detector, in parallel with the display of the inspection and replacement of the AC line-to-line voltage detector in which the abnormality is recommended, the abnormal AC line-to-line voltage detection value is replaced with the corresponding AC line-to-line voltage estimation value, so that the operation can be continued, and the risk of the unscheduled stop of the system provided with the power conversion device can be reduced. For example, thereby, the operation of the system coping with the operation continuation can be performed until the next periodic inspection, and in the periodic inspection, the replacement of the determined abnormal AC line-to-line voltage detector and the like can be promptly performed.

[0165] Further, in Embodiments 3 and 4, the case where the 3-level converter is used is explained, but it is not limited thereto. Even in the case where the 2-level converter is used, the same application can be made.

[0166] The above explained embodiments include the matters shown below. However, the matters included in the above explained embodiments are not limited to the matters shown below.

[0167] (Matter 1)

[0168] A power conversion device has:

[0169] a converter that converts an AC input into a plurality of potentials;

[0170] an inverter that converts a voltage of the plurality of potentials into an AC output to a motor;

[0171] a smoothing capacitor that is connected between two potentials of the plurality of potentials and that suppresses a potential variation between the potentials;

[0172] 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;

[0173] a current detector that detects an output current of the inverter and outputs the output current of the inverter as an inverter output current;

[0174] an inverter output current controller that generates an inverter output voltage command for the inverter in such a manner that the inverter output current coincides with an inverter output current command;

[0175] a motor voltage calculator that calculates an estimated value of an AC line-to-line voltage of the motor, i.e., a motor voltage estimated value, from the inverter output voltage command and the DC voltage detection value;

[0176] a correction control section that calculates a correction value for correcting a signal for controlling the motor from the motor voltage estimated value;

[0177] an adder that adds the correction value to a control command signal to generate the inverter output current command.

[0178] Thus, an estimated value of an AC line-to-line voltage of the motor is calculated from an inverter output voltage command and a DC voltage detection value, and a correction value for correcting a signal for controlling the motor is calculated from the estimated value, so that high-precision correction control can be performed without using an AC line-to-line voltage detector.

[0179] (Article 2)

[0180] The power conversion device according to Article 1,

[0181] The power conversion device is capable of switching a plurality of modulation schemes,

[0182] The motor voltage calculator calculates the motor voltage estimated value by an operation method corresponding to the modulation scheme of the power conversion device.

[0183] Thus, a power conversion device that can switch a plurality of modulation schemes according to use or the like can be realized.

[0184] (Article 3)

[0185] The power conversion device according to Article 2,

[0186] The power conversion device is a 3-level power conversion device,

[0187] The plurality of modulation schemes include a bipolar modulation scheme,

[0188] The motor voltage calculator includes:

[0189] a pulse width calculator that calculates a pulse width of a positive side and a pulse width of a negative side from the inverter output voltage command;

[0190] a DC voltage variation amount calculator that calculates a variation amount of the DC voltage detection value with respect to a predetermined reference voltage;

[0191] a correction amount calculator that calculates a correction amount using the pulse widths and the variation amount,

[0192] In the bipolar modulation mode, the power conversion device calculates the correction amount using the pulse width calculator, the DC voltage variation amount calculator, and the correction amount calculator, and calculates the motor voltage estimation value by correcting the inverter output voltage command by the correction amount.

[0193] Thus, in the 3-level bipolar modulation mode, high-precision control of the motor can be performed.

[0194] (Paragraph 4)

[0195] The power conversion device according to Paragraph 2,

[0196] The power conversion device is a 3-level power conversion device,

[0197] The plurality of modulation modes include a unipolar modulation mode,

[0198] The motor voltage calculator includes:

[0199] a DC voltage variation ratio calculator that calculates a variation ratio of the DC voltage detection value with respect to a predetermined reference voltage;

[0200] a phase voltage calculator that calculates an AC phase voltage estimation value in a case where the AC voltage command is positive and in a case where the AC voltage command is negative, based on the inverter output voltage command, i.e., the AC voltage command, and the variation ratio,

[0201] In the unipolar modulation mode, the power conversion device calculates the AC phase voltage estimation value by the DC voltage variation ratio calculator and the phase voltage calculator, and outputs the AC phase voltage estimation value corresponding to the polarity of the AC voltage command, thereby generating the motor voltage estimation value.

[0202] Thus, in the 3-level unipolar modulation mode, high-precision control of the motor can be performed.

[0203] (Paragraph 5)

[0204] The power conversion device according to Paragraph 1,

[0205] The power conversion device is a 2-level power conversion device,

[0206] The motor voltage calculator includes a DC voltage variation ratio calculator that calculates a variation ratio of the DC voltage detection value with respect to a predetermined reference voltage,

[0207] The power conversion device calculates the variation ratio by the DC voltage variation ratio calculator, and calculates the motor voltage estimation value based on the inverter output voltage command, i.e., the AC voltage command, and the variation ratio.

[0208] Thus, high-precision control of the motor can be performed in the 2-level modulation system.

[0209] (Items 6)

[0210] A power conversion device has:

[0211] a converter that converts an AC input into a plurality of potentials;

[0212] an inverter that converts voltages of the plurality of potentials into an AC output to a motor;

[0213] a smoothing capacitor connected between two of the plurality of potentials for suppressing a potential variation between the potentials;

[0214] 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;

[0215] an AC line-to-line voltage detector that detects an output voltage of the inverter and outputs the same as a motor voltage detection value;

[0216] a correction control section that calculates a correction value for correcting a signal for controlling the motor based on the motor voltage detection value;

[0217] a summer that adds the correction value to a control command signal to generate an inverter output current command;

[0218] a current detector that detects an output current of the inverter and outputs the same as an inverter output current;

[0219] an inverter output current controller that generates an inverter output voltage command for the inverter in such a manner that the inverter output current coincides with the inverter output current command;

[0220] a motor voltage calculation section that calculates an estimated value of an AC line-to-line voltage of the motor, i.e., a motor voltage estimated value, based on the inverter output voltage command and the DC voltage detection value;

[0221] an AC line-to-line voltage detector abnormality determiner that determines an abnormality of the AC line-to-line voltage detector based on the motor voltage estimated value.

[0222] Thus, an estimated value of an AC line-to-line voltage of a motor is calculated based on an inverter output voltage command and a DC voltage detection value, and an abnormality of an AC line-to-line voltage detector is determined based on the estimated value, so that the abnormality of the AC line-to-line voltage detector can be detected in a configuration using the AC line-to-line voltage detector.

[0223] (Item 7)

[0224] The power conversion device according to Item 6,

[0225] The AC line-to-line voltage detector abnormality determiner determines that a wiring connected to an AC line-to-line voltage detector whose output is below a predetermined threshold value is abnormal.

[0226] Thus, in a configuration using an AC line-to-line voltage detector, it is also possible to detect an abnormality in a wiring connected to the AC line-to-line voltage detector.

[0227] (Item 8)

[0228] The power conversion device according to Item 6,

[0229] The power conversion device further includes an abnormality-time calculated value switcher that, when an AC line-to-line voltage detector is determined to be abnormal by the AC line-to-line voltage detector abnormality determiner, inputs the motor voltage estimated value calculated by the motor voltage calculation section to the correction control section instead of the motor voltage detection value from the AC line-to-line voltage detector determined to be abnormal.

[0230] Thus, when an abnormality in an AC line-to-line voltage detector is determined, the motor voltage estimated value calculated by the motor voltage calculation section is switched in accordance with the motor voltage detection value from the AC line-to-line voltage detector that has become abnormal, and therefore, in a configuration using an AC line-to-line voltage detector, even if an AC line-to-line voltage detector becomes abnormal, it is possible to normally continue control of the motor.

[0231] (Item 9)

[0232] The power conversion device according to any one of Items 6 to 8,

[0233] The AC line-to-line voltage detector abnormality determiner causes a display to display information related to the abnormality when it is determined that an abnormality has occurred in an AC line-to-line voltage detector.

[0234] Thus, when an abnormality in an AC line-to-line voltage detector is determined, information related to the abnormality is displayed, and therefore, in a configuration using an AC line-to-line voltage detector, it is possible to easily recognize an abnormality in an AC line-to-line voltage detector.

[0235] (Item 10)

[0236] A motor control method for a power conversion device that includes:

[0237] a converter that converts an AC input into a plurality of potentials;

[0238] an inverter that converts a voltage of the plurality of potentials into an alternating-current output to the motor;

[0239] a smoothing capacitor connected between two of the plurality of potentials for suppressing a potential variation between the potentials;

[0240] a direct-current voltage detector that detects a potential difference between the potentials to which the smoothing capacitor is connected as a direct-current voltage detection value,

[0241] wherein an output current of the inverter is detected as an inverter output current;

[0242] an inverter output voltage command for the inverter is generated in a manner such that the inverter output current coincides with an inverter output current command;

[0243] a motor voltage estimation value that is an estimation value of an alternating-current line-to-line voltage of the motor is calculated from the inverter output voltage command and the direct-current voltage detection value;

[0244] a correction value that corrects a signal for controlling the motor is calculated from the motor voltage estimation value;

[0245] the correction value is added to a control command signal to generate the inverter output current command.

[0246] (Article 11)

[0247] An abnormality detection method for detecting an abnormality in a power conversion device that includes:

[0248] a converter that converts an alternating-current input into a plurality of potentials;

[0249] an inverter that converts a voltage of the plurality of potentials into an alternating-current output to the motor;

[0250] a smoothing capacitor connected between two of the plurality of potentials for suppressing a potential variation between the potentials;

[0251] a direct-current voltage detector that detects a potential difference between the potentials to which the smoothing capacitor is connected as a direct-current voltage detection value;

[0252] an alternating-current line-to-line voltage detector that detects an output voltage of the inverter and outputs the same as a motor voltage detection value,

[0253] wherein

[0254] a correction value that corrects a signal for controlling the motor is calculated from the motor voltage detection value;

[0255] adding the correction value to a control command signal to generate an inverter output current command;

[0256] detecting an output current of the inverter as an inverter output current;

[0257] generating an inverter output voltage command for the inverter in such a manner that the inverter output current coincides with the inverter output current command;

[0258] calculating a motor voltage estimation value, which is an estimation value of an AC line-to-line voltage of the motor, from the inverter output voltage command and the DC voltage detection value;

[0259] judging an abnormality of the AC line-to-line voltage detector based on the motor voltage estimation value.

Claims

1. A power conversion device, characterized by, has: a converter that converts an AC input into a plurality of potentials; an inverter that converts voltages of the plurality of potentials into an AC output to a motor; a smoothing capacitor that is connected between two of the plurality of potentials for suppressing a 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 as an inverter output current and outputs the inverter output current; an inverter output current controller that generates an inverter output voltage command for the inverter in such a manner that the inverter output current coincides with an inverter output current command; a motor voltage calculator that calculates an estimated value of an AC line-to-line voltage of the motor, that is, a motor voltage estimated value, from the inverter output voltage command and the DC voltage detection value; a correction control unit that calculates a correction value that corrects a control command signal for controlling the motor from the motor voltage estimated value; an adder that adds the correction value to the control command signal to generate the inverter output current command.

2. The power conversion device according to claim 1, wherein the power conversion device is capable of switching a plurality of modulation methods, the motor voltage calculator calculates the motor voltage estimated value by an operation method corresponding to the modulation method of the power conversion device.

3. The power conversion device according to claim 2, wherein the power conversion device is a 3-level power conversion device, a bipolar modulation method is included in the plurality of modulation methods, the motor voltage calculator includes: a pulse width calculator that calculates pulse widths of positive and negative sides from the inverter output voltage command; a DC voltage variation amount calculator that calculates a variation 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 widths 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 amount calculator, and the correction amount calculator, and calculates the motor voltage estimated value by correcting the inverter output voltage command by the correction amount.

4. The power conversion device according to claim 2, wherein the power conversion device is a 3-level power conversion device, the plurality of modulation methods include a unipolar modulation method, the motor voltage calculator includes: a DC voltage variation ratio calculator that calculates a variation ratio of the DC voltage detection value with respect to a predetermined reference voltage; a phase voltage calculator that calculates an AC phase voltage estimated value in a case where the AC voltage command is positive and in a case where the AC voltage command is negative from the inverter output voltage command, that is, an AC voltage command, and the variation ratio. In the single-pole modulation mode, the power conversion device calculates the AC phase voltage estimation value by the DC voltage variation ratio calculator and the phase voltage calculator, outputs the AC phase voltage estimation value corresponding to the polarity of the AC voltage command, and thereby generates the motor voltage estimation value.

5. The power conversion device according to claim 1, wherein the power conversion device is a 2-level power conversion device, the motor voltage calculator includes a DC voltage variation ratio calculator that calculates a variation 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 estimation value from the inverter output voltage command, i.e., the AC voltage command, and the variation ratio.

6. A power conversion device, characterized by, has: a converter that converts an AC input into a plurality of potentials; an inverter that converts a voltage of the plurality of potentials into an AC output to a motor; a smoothing capacitor that is connected between two of the plurality of potentials, and that suppresses a 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; an AC line-to-line voltage detector that detects an output voltage of the inverter and outputs the detected output voltage as a motor voltage detection value; a correction control unit that calculates a correction value that corrects a control command signal for controlling the motor, based on the motor voltage detection value; an adder that adds the correction value to the control command signal, and generates an inverter output current command; 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 voltage command generator that generates an inverter output voltage command for the inverter in such a manner that the inverter output current coincides with the inverter output current command; a motor voltage calculation unit that calculates an estimation value of an AC line-to-line voltage of the motor, i.e., a motor voltage estimation value, based on the inverter output voltage command and the DC voltage detection value; an AC line-to-line voltage detector abnormality determiner that determines an abnormality of the AC line-to-line voltage detector based on the motor voltage estimation value.

7. The power conversion device according to claim 6, wherein the AC line-to-line voltage detector abnormality determiner determines that there is an abnormality in a wiring connected to the AC line-to-line voltage detector that outputs the AC line-to-line voltage detection value that is below a predetermined threshold value.

8. The power conversion device according to claim 6, wherein the power conversion device further includes an abnormality-time calculation value switcher that, when the AC line-to-line voltage detector abnormality determiner determines that there is an abnormality in the AC line-to-line voltage detector, inputs 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-to-line voltage detector that is determined to have the abnormality.

9. The power conversion device according to any one of claims 6 to 8, wherein The AC line-to-line voltage detector abnormality determiner displays information related to the abnormality on the display when it is determined that the AC line-to-line voltage detector has an abnormality.

10. A motor control method of a power conversion device, the power conversion device including: a converter that converts an AC input into a plurality of potentials; an inverter that converts voltages of the plurality of potentials into an AC output to a motor; a smoothing capacitor connected between two of the plurality of potentials for suppressing a potential variation between the potentials; and 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, characterized by: detecting an output current of the inverter as an inverter output current; generating an inverter output voltage command for the inverter in such a manner that the inverter output current coincides with an inverter output current command; calculating a motor voltage estimation value that is an estimation value of an AC line-to-line voltage of the motor from the inverter output voltage command and the DC voltage detection value; calculating a correction value that corrects a control command signal for controlling the motor from the motor voltage estimation value; and adding the correction value to the control command signal to generate the inverter output current command.

11. An abnormality detection method for detecting an abnormality in a power conversion device, the power conversion device including: a converter that converts an AC input into a plurality of potentials; an inverter that converts voltages of the plurality of potentials into an AC output to a motor; a smoothing capacitor connected between two of the plurality of potentials for suppressing a 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; and an AC line-to-line voltage detector that detects an output voltage of the inverter and outputs the detected voltage as a motor voltage detection value, characterized by: calculating a correction value that corrects a control command signal for controlling the motor from the motor voltage detection value; adding the correction value to the 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 in such a manner that the inverter output current coincides with the inverter output current command; calculating a motor voltage estimation value that is an estimation value of an AC line-to-line voltage of the motor from the inverter output voltage command and the DC voltage detection value; and determining an abnormality of the AC line-to-line voltage detector based on the motor voltage estimation value. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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