Power conversion device and electric motor control method

Abstract

To provide a technique that allows accurate correction control without using an AC line voltage detector.SOLUTION: A power conversion device has: a converter; an inverter that converts voltage having a plurality of potentials into AC output to an electric motor; a DC voltage detector that detects the potential difference between two potentials in the plurality of potentials as a DC voltage detection value; a current detector that detects output current from the inverter and outputs it as inverter output current; an inverter output current controller that generates an inverter output voltage command to the inverter so that the inverter output current matches an inverter output current command; an electric motor voltage operator that calculates an electric motor voltage estimation value that is an estimation value of the AC line voltage of the electric 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 electric motor from the electric motor voltage estimation value; and an adder that adds the correction value to a control command signal to generate the inverter output current command.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a power conversion device including an inverter that drives an electric motor. [Background technology]

[0002] As a power converter for driving an electric motor, a power converter that converts the power of an AC power source into power with variable voltage and variable frequency is known. The main circuit of this power converter includes a converter that converts AC to DC, a DC circuit connected to the converter, and an inverter that is connected to the converter via the DC circuit and converts DC to AC, and the DC circuit includes a smoothing capacitor. This power converter controls the speed and torque of the electric motor by varying the magnitude and frequency of the AC voltage applied to the motor with the inverter.

[0003] A speed control system and a current control system are used as the control system for the motor. The speed control system detects the speed of the motor with a speed detector and feeds back the detected value by the speed detector. The current control system detects the current flowing through the motor with a current detector and feeds back the detected value by the current detector. There is also a method of making corrections to command values ​​to improve the accuracy of motor control (Patent Documents 1 and 2).

[0004] There is a method to detect the AC line voltage of a motor with an AC line voltage detector and apply corrections to the control using the detected value. For example, in the control of an induction motor, the slip amount and speed electromotive voltage of the induction motor are controlled, but there is a risk of accuracy degradation due to deviations between the design values ​​and actual values ​​and characteristic changes of the motor's resistance and mutual inductance. Therefore, there is a correction control method in which the deviation between the design value and the actual value is extracted from the detection value of the AC line voltage of the motor, and a correction amount is applied to the slip amount and excitation current to make the deviation zero. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-208397 A [Patent Document 2] Japanese Patent Application Publication No. 09-149658 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned method of correcting control using a detected value of an AC line voltage, the AC line voltage detector detects the output voltage from a semiconductor element in the power converter. The output voltage is a square wave caused by switching, and the detected value contains a large ripple component, which may degrade accuracy.

[0007] Furthermore, if a filter circuit with a large time constant is used to reduce this large ripple component and the output of the filter circuit is detected, a delay will occur in the detection of the output voltage, and this delay may result in a deterioration in accuracy.

[0008] Furthermore, in a configuration using an AC line voltage detector, an abnormality may occur in the AC line voltage detector, which may result in a deterioration in the accuracy of correction control or, in the worst case, an unplanned stoppage.

[0009] One object of the present disclosure is to provide a technique that enables highly accurate correction control without using an AC line voltage detector.

[0010] Another object of the present disclosure is to provide a technique that enables detection of an abnormality in an AC line voltage detector in a configuration that uses an AC line voltage detector. [Means for solving the problem]

[0011] A power conversion device according to one embodiment of the present disclosure includes a converter that converts an AC input into a plurality of potentials, an inverter that converts the voltage of the plurality of potentials into an AC output to an electric motor, a smoothing capacitor that is connected between two of the plurality of potentials and suppresses potential fluctuations 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 it 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 matches an inverter output current command, a motor voltage calculator that calculates a motor voltage estimate that is an estimate of the AC 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 that corrects a signal for controlling the motor from the motor voltage estimate value, and an adder that adds the correction value to a control command signal to generate the inverter output current command.

[0012] A power conversion device according to another aspect of the present disclosure includes 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 an electric motor, a smoothing capacitor that is connected between two of the plurality of potentials and suppresses potential fluctuations 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 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 for correcting a signal for controlling the electric motor from the motor voltage detection value, and a control circuit that controls the correction value. the inverter output current controller generates an inverter output voltage command to the inverter so that the inverter output current matches the inverter output current command; a motor voltage calculation unit calculates a motor voltage estimate that is an estimate of the AC line voltage of the motor from the inverter output voltage command and the DC voltage detection value; and an AC line voltage detector abnormality determiner that determines an abnormality in the AC line voltage detector based on the motor voltage estimate. Effect of the Invention

[0013] According to one aspect of the present disclosure, an estimate of the AC line voltage of the motor is calculated from the inverter output voltage command and the detected DC voltage, and a correction value for correcting a signal for controlling the motor is calculated from the estimate, thereby enabling highly accurate correction control without using an AC line voltage detector.

[0014] According to another aspect of the present disclosure, an estimate of the AC line voltage of the motor is calculated from the inverter output voltage command and the DC voltage detection value, and an abnormality in the AC line voltage detector is determined based on the estimate, thereby making it possible to detect an abnormality in the AC line voltage detector in a configuration that uses an AC line voltage detector. [Brief description of the drawings]

[0015] [Figure 1]1 is an overall configuration diagram of a power conversion device according to a first embodiment. [Diagram 2] FIG. 4 is a diagram showing the magnetic flux saturation characteristics of a motor. [Diagram 3] FIG. 13 is a diagram showing the relationship between speed, excitation current, and speed electromotive force. [Figure 4] FIG. 1 is a diagram showing a configuration of a conventional power conversion device for comparison with the power conversion device of the present embodiment. [Diagram 5] FIG. 2 is a diagram for explaining the configuration of a three-level motor voltage calculator 70. [Figure 6] FIG. 13 is a diagram illustrating the relationship between a voltage command and an output rectangular wave voltage in a dipolar state. [Figure 7] FIG. 2 is a diagram for explaining a three-level dipolar modulation voltage calculator 71. [Figure 8] 5A and 5B are diagrams illustrating the relationship between a voltage command and an output rectangular wave voltage during unipolar modulation. [Figure 9] FIG. 2 is a diagram for explaining a three-level unipolar modulation voltage calculator 72. [Figure 10] FIG. 11 is an overall configuration diagram of a power conversion device according to a second embodiment. [Figure 11] FIG. 2 is a diagram for explaining a two-level motor voltage calculator 80. [Figure 12] FIG. 13 is a diagram for explaining the relationship between a voltage command and an output rectangular wave voltage in the case of two levels. [Figure 13] FIG. 2 is a diagram for explaining a two-level modulation voltage calculator 81. [Figure 14] FIG. 11 is an overall configuration diagram of a power conversion device according to a third embodiment. [Figure 15] 4 is a flowchart of an abnormality diagnosis for an AC line voltage detector. [Figure 16] FIG. 11 is an overall configuration diagram of a power conversion device according to a fourth embodiment. [Figure 17] FIG. 13 is a diagram for explaining an abnormality-time calculation value switch 92. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Some embodiments will be described with reference to the drawings. Note that the embodiments described below do not limit the invention according to the claims, and all of the elements and combinations thereof described in the embodiments are not necessarily essential to the solution of the invention. EXAMPLES

[0017] In the first embodiment, a power conversion device using a three-level converter is illustrated.

[0018] FIG. 1 is a diagram of an overall configuration of a power conversion device according to a first embodiment.

[0019] The power conversion device 100 is a device that converts AC power from an AC power source 1 to drive an electric motor 4. The power conversion device 100 includes a converter unit (also called a converter) 2 that converts AC power from the AC power source 1 into DC power, an inverter unit (also called an inverter) 3 that converts the DC power output by the converter unit 2 into desired AC power and drives the electric motor 4, a converter control device 5 that controls the converter unit 2, and an inverter control device 6 that controls the inverter unit 3.

[0020] The converter unit 2 is a so-called three-level converter, which converts AC power into DC power with a positive potential (first potential) level, a neutral point (zero) potential (second potential) level, and a negative potential (third potential) level. The inverter unit 3 is a so-called three-level inverter, which converts DC power with 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 electric motor 4. Between the converter unit 2 and the inverter unit 3, the positive potential level is connected by a P wiring 40, the neutral point potential level is connected by a C wiring 41, and the negative potential level is connected by an N wiring 42.

[0021] The converter unit 2 includes a converter power conversion section 21, a converter P-side smoothing capacitor 22 and a converter N-side smoothing capacitor 23 for suppressing fluctuations in DC voltage, a converter P-side DC voltage detector 25 for measuring the terminal voltage of the converter P-side smoothing capacitor 22, a converter N-side DC voltage detector 26 for measuring the terminal voltage of the converter N-side smoothing capacitor 23, and a converter neutral resistor 24 connected to the C wiring 41 for suppressing DC resonance.

[0022] The inverter unit 3 includes an inverter power conversion section 31, an inverter P-side smoothing capacitor 32 connected between a positive potential level and a neutral potential level and suppressing potential fluctuations between these potentials, an inverter N-side smoothing capacitor 33 connected between the neutral potential level and a negative potential level and suppressing potential fluctuations between these potentials, an inverter P-side DC voltage detector 35 for measuring the terminal voltage of the inverter P-side smoothing capacitor 32, an inverter N-side DC voltage detector 36 for measuring the terminal voltage of the inverter N-side smoothing capacitor 33, and an inverter neutral point resistor 34 connected to a C wiring 41 and for suppressing DC resonance.

[0023] 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.

[0024] The inverter control device 6 controls the inverter power conversion unit 31 so that the output torque and speed of the electric motor 4 satisfy desired characteristics. The configuration of the inverter control device 6 will be described later.

[0025] The power conversion device 100 further includes a current detector 7 that detects and outputs the output current of the converter unit 2, a speed detector 8 directly connected to the motor 4 that detects and outputs the speed of the motor 4, and a current detector 9 that detects and outputs the output current of the inverter unit 3.

[0026] A signal (output signal) of the detection value detected by the current detector 7 is input to the converter control device 5. In addition, signals (output signals) of the detection values ​​detected by the DC voltage detectors 25, 26 are also input to the converter control device 5. The converter control device 5 performs various calculation processes based on these input detection values, and outputs a signal to control the converter power conversion unit 21.

[0027] A signal (output signal) of the detection value detected by the speed detector 8 and a signal (output signal) of the detection value detected by the current detector 9 are input to the inverter control device 6. The inverter control device 6 performs various calculation processes based on these input detection values, and outputs a signal to control the inverter power conversion unit 31.

[0028] 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 .

[0029] The DC voltage command generator 51 outputs a DC voltage command value, which is a command value of the DC voltage to be outputted from the converter unit 2, to the DC voltage controller 52.

[0030] 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 DC voltage detection values ​​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 sum of the DC voltage detection values ​​input from the DC voltage detector 25 and the DC voltage detector 26 matches the DC voltage command value.

[0031] The neutral point voltage controller 55 calculates a voltage command such that the neutral point voltage becomes zero based on the difference between the detection values ​​of the DC voltages input from the DC voltage detectors 25 and 26 , and outputs the voltage command to the current controller 53 .

[0032] The current controller 53 calculates a converter voltage command value so that the converter output current detection value output from the current detector 7 coincides with the converter output current command value input from the DC voltage controller 52, and outputs the calculated 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.

[0033] The pulse generator 54 calculates a pulse signal for controlling the on / off of each switching element of the converter power conversion unit 21 so that the output voltage by 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.

[0034] 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 .

[0035] The speed command generator 61 outputs a speed command value, which is a command value for the speed at which the electric motor 4 is operated, to the speed controller 62 .

[0036] The speed controller 62 calculates a torque current command value for the motor so 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 for the motor to a current controller 63. Here, the combination of the torque current command value for the motor and an excitation current command value for the motor, which will be described later, is called an inverter output current command value.

[0037] The neutral point voltage controller 65 calculates a voltage command such that the neutral point voltage becomes zero based on the difference between the detected DC voltage values ​​input from the DC voltage detector 35 and the DC voltage detector 36, and outputs the voltage command to the current controller 63.

[0038] The current controller 63 calculates an inverter voltage command value so 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.

[0039] The pulse generator 64 generates a pulse signal for controlling the on / off of each switching element of the inverter power conversion unit 31 so that the output voltage from 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.

[0040] Next, a configuration for implementing correction control for improving the accuracy of control over the electric motor 4 in the power conversion device 100 will be described.

[0041] The inverter control device 6 of the power conversion device 100 further includes an excitation current command generator 66, a magnetic flux controller 67, a correction controller 68, an adder 69, and a three-level motor voltage calculator .

[0042] When the motor to be controlled is, for example, an induction motor, the control device controls the excitation current to set the magnetic flux of the induction motor to a predetermined value. Also, to effectively utilize the control range of the induction motor, a control is used that varies the magnetic flux according to the speed. To achieve this, the excitation current command generator 66 outputs a reference excitation current command value for setting the magnetic flux of the motor 4 to a magnetic flux controller 67. The magnetic flux controller 67 receives the speed detection value output from the speed detector 8 as an input, calculates and outputs an excitation current command value obtained by varying the reference excitation current command value according to the speed detection value.

[0043] Before explaining the correction control, the influence of magnetic flux saturation of the motor will be explained. As shown in formula (1), the magnetic flux Φ of the motor is the product of the excitation inductance M and the excitation current Im of the motor.

[0044] Φ = M × Im … (1)

[0045] FIG. 2 is a diagram showing the magnetic flux saturation characteristics of the motor.

[0046] In the magnetic flux controller 67, when the excitation current is controlled to be reduced inversely proportional to the speed from a certain speed (called "base speed") to the maximum speed (called "top speed"), the speed electromotive force (=speed x magnetic flux) of the motor can be made constant from the base speed to the top speed. Figure 3 is a diagram showing the relationship among the speed, the excitation current, and the speed electromotive force.

[0047] However, as shown in Fig. 2, when there is magnetic flux saturation, the excitation inductance M increases as the magnetic flux decreases. In other words, M_Top>M_Base. Therefore, in a control that reduces the excitation current in inverse proportion to the speed, there is a risk that the magnetic flux and the speed electromotive voltage will become larger than expected. And, if the effect of the increase in the speed electromotive voltage exceeds the output voltage of the power conversion device, there is a risk that it will become impossible to control.

[0048] Therefore, correction control is performed to suppress the increase in the speed electromotive voltage caused by the influence of magnetic flux saturation of the motor.

[0049] Fig. 4 is a diagram showing the configuration of a conventional power conversion device for comparison with the power conversion device of this embodiment. In Fig. 4, the same components as those of the power conversion device according to the first embodiment shown in Fig. 1 are given the same reference numerals. The power conversion device 101 of Fig. 4 includes an AC line voltage detector 10 and a filter circuit 11, and an AC line voltage detection value output by the AC line voltage detector 10 is input to a correction controller 68 via the filter circuit 11. When the AC line voltage detection value is larger than expected, the correction controller 68 calculates and outputs a correction value for lowering the excitation current.

[0050] The adder 69 adds the correction value from the correction controller 68 to the excitation current command value output from the magnetic flux controller 67. Specifically, in the case of magnetic flux saturation as shown in FIG. 2, when the magnetic flux controller 67 outputs an excitation current command value inversely proportional to the speed, the speed electromotive voltage increases. Therefore, the correction controller 68 outputs a negative correction value that further reduces the excitation current so that the actual speed electromotive voltage 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) that is smaller than the inversely proportional value as shown in the middle part of FIG. 3, and as a result, the speed electromotive voltage becomes constant.

[0051] By performing correction control in this way, it is possible to suppress an increase in the speed electromotive voltage of the motor. However, in the conventional method using the AC line voltage detector 10 as shown in FIG. 4, the detection accuracy is poor because the detected voltage value is a square wave. If a filter circuit with a large time constant is inserted to reduce the ripple of the square wave, there is a problem that the accuracy of the correction control decreases due to delay. In addition, there is a risk of malfunction due to an abnormality in the AC line voltage detector 10.

[0052] The power conversion device 100 according to this embodiment has the following measures taken to address these issues.

[0053] The three-level motor voltage calculator 70 according to the first embodiment will be specifically described.

[0054] 1, a three-level motor voltage calculator 70 receives as input 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. The three-level motor voltage calculator 70 uses these input signals to calculate AC line voltage estimates (Vuvh, Vvwh) of the motor 4. The AC line voltage estimates of the motor 4 are input to a correction controller 68.

[0055] Next, the three-level motor voltage calculator 70 according to the first embodiment will be described more specifically.

[0056] FIG. 5 is a diagram for explaining the configuration of the three-level motor voltage calculator 70. As shown in FIG.

[0057] The three-level motor voltage calculator 70 includes a three-level dipolar modulation voltage calculator 71, a three-level unipolar modulation voltage calculator 72, a correction calculation selection unit 73, and an AC line voltage calculator 74.

[0058] The three-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, there are three-level inverters using dipolar modulation used at low voltages and unipolar modulation used at high voltages, and the calculation method of the motor voltage differs for each modulation method. Therefore, the correction calculation selection unit 73 selects whether to output a dipolar or unipolar motor AC phase voltage estimate value based on a signal indicating dipolar or unipolar. The signal indicating dipolar or unipolar is, for example, a voltage command value. It is sufficient to determine that the voltage command value is unipolar when it is larger than a certain set value, and dipolar when it is smaller.

[0059] Then, the AC line voltage calculator 74 calculates and outputs the motor AC line voltage estimates (Vuvh, Vvwh) from the motor AC phase voltage estimates (Vuh, Vvh, Vwh) selected by the correction calculation selection unit 73.

[0060] Next, the calculation method of the estimated motor AC phase voltage value will be described for each of the dipolar modulation and unipolar modulation.

[0061] <Calculation method for dipolar modulation>

[0062] First, the calculation of the estimated motor AC phase voltage value during three-level dipolar modulation will be described.

[0063] FIG. 6 is a diagram for explaining the relationship between a voltage command and an output rectangular wave voltage in the dipolar mode.

[0064] A power conversion device converts the magnitude of a voltage command into a pulse width and controls the on / off of each switching element in the power conversion section to output a voltage that matches the command as an average voltage. In the case of dipolar modulation, a pulse signal is generated so 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 outputting zero voltage, the positive and negative sides are made to have the same pulse width, making the average voltage zero.

[0065] Here, if the positive DC voltage Ep and the negative DC voltage En are the same, that is, if the positive and negative sides are balanced, the voltage will be zero. However, if the positive DC voltage Ep and the negative DC voltage En are different, that is, if the positive and negative sides are unbalanced, the voltage will not be zero. Therefore, when estimating and calculating the AC phase voltage of an actual motor, it is necessary to take into account the fluctuation due to the DC voltage. However, in dipolar modulation, the output voltage is determined by the difference between the Ep side and the En side, so the AC phase voltage of the motor cannot be estimated by reflecting the ratio of Ep or En in the voltage command. Therefore, in this embodiment, the estimation is performed by adding a correction amount to the original voltage command as follows. That is, the correction amount ΔVh is calculated by the formula (2).

[0066] ΔVh=Vdb×α×ΔEp-Vdb×(1-α)×ΔEn …(2)

[0067] Here, Vdb is the reference voltage command for dipolar operation, and α indicates the pulse width on the Ep side and is calculated using equation (3).

[0068] α = (AC voltage command% + 50%) / 100% … (3)

[0069] For example, when expressing a voltage command of 50% or less with dipolar modulation, by setting Vdb to 50% voltage, the pulse width on the Ep side to α calculated using equation (3), and the pulse width on the En side to 1-α, when the voltage command is 25%, it is possible to obtain 50% voltage x (75 / 100) - 50% voltage x (1 - 75 / 100) = 25% voltage. The correction amount is calculated by taking into account the fluctuations of Ep and En. ΔEp is the fluctuation of Ep and is calculated using equation (4). ΔEn is the fluctuation of En and is calculated using equation (5).

[0070] ΔEp = EpFB / Eb-1 … (4)

[0071] ΔEn = EnFB / Eb-1 … (5)

[0072] Here, EpFB is the P-side DC voltage detection value detected and output by DC voltage detector 35. EnFB is the N-side DC voltage detection value detected and output by DC voltage detector 36. Eb indicates the reference value of the DC voltage. When there is no variation from the reference value, ΔEp and ΔEn are zero.

[0073] For example, assuming that there is a 1.1-fold fluctuation on the Ep side and a 0.9-fold fluctuation on the En side, the output voltage when the voltage command is 0% will be 50% voltage x (50 / 100) x 1.1-50% voltage x (1-50 / 100) x 0.9 = 5% voltage. Furthermore, according to formula (2), the correction amount ΔVh = 50% voltage x (50 / 100) x 0.1-50% voltage x (1-50 / 100) x (-0.1) = 5%. An estimated value of the motor AC phase voltage can be obtained by adding the correction amount ΔVh = 5% to the voltage command of 0%.

[0074] FIG. 7 is a diagram for explaining the three-level dipolar modulation voltage calculator 71. As shown in FIG.

[0075] The three-level dipolar modulation voltage calculator 71 receives the AC phase voltage command values ​​(Vuref, Vvref, Vwref) and the DC voltage detection values ​​(EpFB, EnFB) as inputs, calculates α for each phase according to equation (3) in the Ep side pulse width calculator 711, and outputs αu, αv, and αw. The DC voltage fluctuation calculator 712 calculates and outputs ΔEp and ΔEn from EpFB and EnFB according to equations (4) and (5). ΔEp, ΔEn, αu, αv, and αw are input to a correction amount calculator 713.

[0076] A correction amount calculator 713 calculates and outputs correction amounts ΔVhu, ΔVhv, and ΔVhw for each phase according to equation (2). The correction amounts ΔVhu, ΔVhv, and ΔVhw are input to a dipolar motor phase voltage calculator 714 together with an AC phase voltage command value. The dipolar motor phase voltage calculator 714 adds the correction amount to the AC phase voltage command for each phase to calculate and output motor AC phase voltage estimate values ​​Vuh_d, Vvh_d, and Vwh_d during dipolar modulation.

[0077] <Calculation method for unipolar modulation>

[0078] Next, the calculation of the estimated motor AC phase voltage value during three-level unipolar modulation will be described.

[0079] FIG. 8 is a diagram for explaining the relationship between a voltage command and an output rectangular wave voltage during unipolar modulation.

[0080] In the case of unipolar modulation, unlike dipolar modulation, a pulse signal is generated so that the area that changes depending on the pulse width on the positive and negative sides matches the command. For example, when outputting a 50% voltage, the positive side has a 50% pulse width, and the average voltage is 50%.

[0081] At this time, if the positive DC voltage Ep fluctuates with respect to the reference, the output will not be 50% voltage. Therefore, when estimating and calculating the AC phase voltage of an actual motor, it is necessary to take into account the fluctuation due to the DC voltage. In the case of unipolar modulation, it is sufficient to reflect the fluctuation ratio of Ep in the voltage command. Similarly, the negative side can be calculated by reflecting the fluctuation ratio of En in the voltage command. Therefore, in this embodiment, the estimated value of the AC phase voltage is calculated by multiplying the original voltage command by the fluctuation ratio, as shown in equations (6) and (7).

[0082] Vhp = AC voltage command% × Epk (when AC voltage command is positive) … (6)

[0083] Vhn = AC voltage command % × Enk (when the AC voltage command is negative) … (7)

[0084] Here, Epk is the fluctuation ratio of the P-side DC voltage detection value and is calculated by equation (8). Enk is the fluctuation ratio of the N-side DC voltage detection value and is calculated by equation (9).

[0085] Epk = EpFB / Eb ... (8)

[0086] Enk = EnFB / Eb … (9)

[0087] Here, EpFB is the P-side DC voltage detection value detected and output by DC voltage detector 35. EnFB is the N-side DC voltage detection value detected and output by DC voltage detector 36. Eb indicates the reference value of the DC voltage. When the DC voltage does not vary from the reference value, Epk and Enk are 1.

[0088] FIG. 9 is a diagram for explaining the three-level unipolar modulation voltage calculator 72. As shown in FIG.

[0089] The three-level unipolar modulation voltage calculator 72 receives the AC phase voltage command values ​​(Vuref, Vvref, Vwref) and the DC voltage detection values ​​(EpFB, EnFB) as inputs, and calculates and outputs the fluctuation ratios Epk and Enk in a DC voltage fluctuation ratio calculator 721 according to equations (8) and (9). Epk, Enk, Vuref, Vvref, and Vwref are input to a phase voltage calculator 722. The phase voltage calculator 722 calculates and outputs Vhp and Vhn, respectively, according to equations (6) and (7). Vhp and Vhn of each phase are input to a unipolar motor phase voltage calculator 723 together with the AC phase voltage command value. The unipolar motor phase voltage calculator 723 outputs Vhp if the polarity of the AC voltage command value is positive, and outputs Vhn if it is negative. In this manner, the motor AC phase voltage estimates Vuh_u, Vvh_u, Vwh_u in the case of unipolar modulation are generated.

[0090] As described above, in the first embodiment, in the three-level power converter, the fluctuation of the DC voltage is taken into consideration in the AC phase voltage command, the calculation method is switched between dipolar modulation and unipolar modulation, and the motor AC line voltage estimates (Vuvh, Vvwh) are calculated from the motor AC phase voltage estimates (Vuh, Vvh, Vwh), and correction control is performed based on the calculated values. As a result, compared to the case where a conventional motor AC line voltage detector is used, it is possible to perform highly accurate correction control that is not affected by ripple components due to square waves or filter delays. In addition, since no AC line voltage detector is used, risks such as malfunction of correction control or unplanned stoppage due to an abnormality in the AC line voltage detector are eliminated. EXAMPLES

[0091] In the second embodiment, a power conversion device using a two-level converter will be illustrated.

[0092] Fig. 10 is an overall configuration diagram of a power conversion device according to a second embodiment. In a power conversion device 102 of this embodiment shown in Fig. 10, the same components as those of the power conversion device 100 according to the first embodiment shown in Fig. 1 are denoted by the same reference numerals. The power conversion device 102 of the second embodiment differs from the power conversion device 100 shown in Fig. 1 in that it does not have parts related to the neutral point, which are characteristic of a three-level converter, such as converter neutral point resistors 24 and 34 and neutral point voltage controllers 55 and 65, and that a DC voltage detector 37 detects Vdc between the P side and the N side.

[0093] Here, differences between the first and second embodiments will be mainly described.

[0094] In the power conversion device 102 of the second embodiment, 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 magnetic flux controller 67, a correction controller 68, an adder 69, and a two-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 magnetic flux controller 67, the correction controller 68, and the adder 69 are basically the same as those in the first embodiment.

[0095] Here, the two-level motor voltage calculator 80 will be specifically described.

[0096] 10, the inverter voltage command values ​​(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 two-level motor voltage calculator 80. Using these input signals, the two-level motor voltage calculator 80 calculates and outputs AC line voltage estimates (Vuvh, Vvwh) of the motor. The AC line voltage estimates of the motor are input to the correction controller 68.

[0097] Next, the two-level motor voltage calculator 80 according to the second embodiment will be described more specifically.

[0098] 11 is a diagram for explaining a two-level motor voltage calculator 80. The three-level inverter and the two-level inverter have different methods for calculating the motor voltage. The two-level motor voltage calculator 80 includes a two-level modulation voltage calculator 81 and an AC line voltage calculator 82. The two-level motor voltage calculator 80 calculates and outputs motor AC phase voltage estimates (Vuh, Vvh, Vwh) and motor AC line voltage estimates (Vuvh, Vvwh) from AC phase voltage command values ​​(Vuref, Vvref, Vwref) and a DC voltage detection value (VdcFB).

[0099] Next, the calculation of the motor AC phase voltage estimate value in the second embodiment will be described.

[0100] FIG. 12 is a diagram for explaining the relationship between a voltage command and an output rectangular wave voltage in the case of two levels.

[0101] Unlike the 3-level case, in the 2-level case, pulse signals are generated so that the area of ​​a single pulse on both the positive and negative sides matches the command. For example, when outputting a 100% voltage as a voltage command, a pulse signal with a 100% pulse width on the P side is generated. When outputting a 0% voltage, a pulse signal with a 50% pulse width on the P side and a 50% pulse width on the N side is generated. When outputting a -100% voltage, a pulse signal with a 100% pulse width on the N side is generated.

[0102] Here, if the DC voltage Vdc between the P side and N side fluctuates with respect to the reference, the voltage command and the actual output voltage will not match. Therefore, in order to estimate and calculate the actual AC phase voltage of the motor, it is necessary to take into account the fluctuation due to the DC voltage. In the two-level system, the estimated AC phase voltage of the motor can be calculated by reflecting the fluctuation ratio of the DC voltage Vdc in the AC voltage command. Therefore, in this embodiment, the AC phase voltage is estimated and calculated by multiplying the original voltage command by the fluctuation ratio, as shown in equation (10).

[0103] Vh = AC voltage command% × Vdck …(10)

[0104] Here, Vdck is the fluctuation ratio of the DC voltage detection value and is calculated by equation (11).

[0105] Vdck = VdcFB / Vdcb … (11)

[0106] Here, VdcFB is the DC voltage detection value between the P side and the N side detected and output by the DC voltage detector 37. Vdcb indicates the reference value of the DC voltage. When the DC voltage does not vary from the reference value, Vdck becomes 1.

[0107] FIG. 13 is a diagram for explaining the two-level modulation voltage calculator 81. As shown in FIG.

[0108] The AC phase voltage command values ​​(Vuref, Vvref, Vwref) and the DC voltage detection value (VdcFB) are input to the two-level modulation voltage calculator 81. The DC voltage fluctuation ratio calculator 811 calculates and outputs Vdck from VdcFB in accordance with equation (11). Vdck, Vuref, Vvref, and Vwref are input to a phase voltage calculator 812. The phase voltage calculator 812 calculates and outputs motor AC phase voltage estimation values ​​Vuh, Vvh, and Vwh in accordance with equation (10).

[0109] As described above, in the second embodiment, in the two-level converter, the fluctuation of the DC voltage is taken into account in the AC phase voltage command, and the motor AC line voltage estimated value (Vuvh, Vvwh) is calculated from the motor AC phase voltage estimated value (Vuh, Vvh, Vwh), and correction control is performed using this. As a result, correction control can be performed with high accuracy without being affected by ripple components due to square waves or filter delays, as compared to the case where a conventional motor AC line voltage detector is used. In addition, since an AC line voltage detector is not used, risks such as malfunction of correction control and unplanned stoppage due to an abnormality in the AC line voltage detector can be eliminated.

[0110] In the correction control in this embodiment, the fluctuation of the speed electromotive voltage caused by the change in excitation inductance due to magnetic flux saturation is controlled to a predetermined value by correcting the excitation current based on the motor voltage estimated value in this embodiment. In addition, the slip control error caused by the change in the secondary resistance of the motor can also be appropriately controlled by correcting the slip amount based on the motor voltage estimated value in this embodiment. EXAMPLES

[0111] In the third embodiment, a power conversion device having an AC line voltage detector and a self-check function for diagnosing an abnormality in the AC line voltage detector in a configuration in which the detected value is used for correction control will be exemplified.

[0112] FIG. 14 is a diagram of an overall configuration of a power conversion device according to a third embodiment.

[0113] In a power conversion device 103 of the present embodiment shown in Fig. 14, the same components as those in the power conversion device 100 according to the first embodiment shown in Fig. 1 are denoted by the same reference numerals. The power conversion device 103 of the third embodiment differs 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 in that an AC line voltage detector abnormality determiner 90 and a display 91 are added.

[0114] Here, differences between the first and second embodiments in the third embodiment will be mainly described.

[0115] As described above, in a device equipped with an AC line voltage detector, an unplanned stop may occur due to a malfunction of correction control caused by an abnormality in the AC line voltage detector. Therefore, the power conversion device 103 of the third embodiment is configured to diagnose an abnormality in the AC line voltage detector by using an estimated motor voltage value.

[0116] Next, the AC line voltage detector abnormality determiner 90 according to the third embodiment will be specifically described.

[0117] 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 magnetic flux controller 67, a correction controller 68, an adder 69, a three-level motor voltage calculator 70, an AC line voltage detector abnormality determiner 90, and a display 91. The speed command generator 61, the speed controller 62, the current controller 63, the pulse generator 64, the neutral point voltage controller 65, the excitation current command generator 66, the magnetic flux controller 67, the correction controller 68, the adder 69, and the three-level motor voltage calculator 70 are basically the same as those in the first embodiment.

[0118] Here, the AC line voltage detector abnormality determiner 90 will be specifically described.

[0119] 14, AC line voltage detector abnormality determiner 90 receives the AC line voltage detection values ​​(VuvFB, VvwFB) from AC line voltage detector 10 via filter circuit 11, and receives the AC line voltage estimation values ​​(Vuvh, Vvwh) of the motor from three-level motor voltage calculator 70. Based on these input signals, AC line voltage detector abnormality determiner 90 performs abnormality diagnosis of the AC line voltage detector.

[0120] FIG. 15 is a flowchart of an abnormality diagnosis for the AC line voltage detector.

[0121] Normally, unless the power converter is stopped, the output of the AC line voltage detector is not zero. If there is some abnormality, such as a break or loosening of the AC line voltage detection loop, only the output of the AC line voltage detector becomes zero.

[0122] In the abnormality diagnosis 201 shown in Fig. 15, if the output of any of the AC line voltage detectors is zero in step 202, then in step 203 it is determined that there is an abnormality in the AC line voltage detection loop at the relevant location, i.e., an abnormality in the wiring connected to the AC line voltage detector, and a message is displayed indicating that there is an abnormality in the AC line voltage detection loop. Note that at this time, if the output of the AC line voltage detector is sufficiently close to zero, it may 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 equal to or lower than a predetermined threshold value, it is determined that there is an abnormality in the AC line voltage detection loop at the relevant location.

[0123] If the output of any of the AC line voltage detectors is not zero in step 202, the estimated U-V AC line voltage value Vuvh is used as a reference and the detected U-V AC line voltage value VuvFB is compared with the reference in step 204. If there is a deviation between the detected U-V AC line voltage value VuvFB and the reference by a predetermined threshold or more, it is determined that there is an abnormality in the AC line voltage detector, and in step 205, a message is displayed to the effect that there is an abnormality in the Vuv AC line voltage detector.

[0124] If there is no deviation of a predetermined threshold or more between the detected AC line voltage value VuvFB between the UV and the estimated AC line voltage value Vuvh between the UV in step 204, the estimated AC line voltage value Vvwh between the V and W is used as a reference and the detected AC line voltage value VvwFB between the V and W is compared with the reference in step 206. If there is a deviation of a predetermined threshold or more between the detected AC line voltage value VvwFB between the V and W and the reference, it is determined that there is an abnormality in the AC line voltage detector, and in step 207, a message is displayed to the effect that there is an abnormality in the Vvw AC line voltage detector.

[0125] If an abnormality is displayed in any of steps 203, 205, and 207, a message prompting inspection and replacement of the abnormal part is displayed in step 208 of FIG. 15, and the series of operations is terminated.

[0126] As described above, in a power conversion device having an AC line voltage detector, by comparing the AC line voltage estimated value with a reference, it is possible to detect an abnormality in the AC line voltage detector and perform efficient maintenance by displaying a message recommending inspection and replacement of the defective AC line voltage detector. EXAMPLES

[0127] In the fourth embodiment, a power conversion device having an AC line voltage detector and a function of continuing operation when an abnormality occurs in the AC line voltage detector in a configuration in which the detection value of the AC line voltage detector is used for correction control is illustrated. Continuing operation by using an alternative signal instead of the detection value when an abnormality occurs in the AC line voltage detector is referred to as a "standby operation."

[0128] FIG. 16 is a diagram of an overall configuration of a power conversion device according to a fourth embodiment.

[0129] In the power conversion device 104 of the fourth embodiment shown in Fig. 16, the same components as those in the power conversion device 103 according to the third embodiment shown in Fig. 14 are denoted by the same reference numerals. The power conversion device 104 of the fourth embodiment differs from the power conversion device 103 of the third embodiment in that a switch 92 for switching an abnormality-time calculation value is additionally provided.

[0130] Here, differences between the fourth embodiment and the third embodiment will be mainly described.

[0131] The abnormality-time calculation value switch 92 receives the AC line voltage detection values ​​(VuvFB, VvwFB) from the AC line voltage detector 10 via the filter circuit 11, together with abnormality determination information indicating whether or not there is an abnormality in the AC line voltage estimate values ​​(Vuvh, Vvwh) of the motor, which is output from the AC line voltage detector abnormality determiner 90. If the abnormality determination information does not indicate that there is an abnormality in the AC line voltage detection value of the motor, the abnormality-time calculation value switch 92 outputs the detection value of the AC line voltage detector 10 to the correction controller 68. However, if the abnormality determination information indicates that there is an abnormality in the AC line voltage detection value of the motor, the abnormality-time calculation value switch 92 outputs a substitute signal to the correction controller 68, instead of the detection value of the abnormal AC line voltage detector 10.

[0132] Next, the abnormality-time calculation value switch 92 according to the fourth embodiment will be specifically described.

[0133] FIG. 17 is a diagram for explaining the abnormality-time calculation value switch 92. As shown in FIG.

[0134] 17, the AC line voltage detection values ​​VuvFB, VvwFB are input to an abnormality calculation value switch 92, and further, an AC line voltage estimate value (Vuvh, Vvwh) and signals indicating whether or not the detection value of AC line voltage detector 10 is abnormal (VuvFB abnormality judgment signal, VvwFB abnormality judgment signal) are input from an AC line voltage detector abnormality determiner 90. The VuvFB abnormality judgment signal is a signal indicating whether or not the AC line voltage detection value VuvFB is abnormal. The VvwFB abnormality judgment signal is a signal indicating whether or not the AC line voltage detection value VvwFB is abnormal.

[0135] If VuvFB is abnormal, the abnormality-time calculation value switch 92 outputs the motor AC line voltage estimate value Vuvh, instead of VuvFB, as Vuvout to the correction controller 68. Also, if VvwFB is abnormal, the abnormality-time calculation value switch 92 outputs the motor AC line voltage estimate value Vvwh, instead of VvwFB, as Vvwout to the correction controller 68. The correction controller 68 calculates a correction amount based on Vuvout and Vvwout.

[0136] As described above, in this embodiment, as in the third embodiment, in a power conversion device having an AC line voltage detector, an abnormality in the AC line voltage detector is determined by performing a comparison with an AC line voltage estimated value as a reference, and a display is displayed recommending inspection and replacement of the defective AC line voltage detector, thereby enabling efficient maintenance.

[0137] Furthermore, in this embodiment, when it is determined that an abnormality exists in an AC line voltage detector, a display is displayed recommending inspection and replacement of the abnormal AC line voltage detector, and at the same time, the abnormal AC line voltage detection value is replaced with the corresponding AC line voltage estimated value, thereby allowing operation to continue and reducing the risk of an unplanned shutdown of a system equipped with a power conversion device. For example, this allows the operation of the system to continue by running the system until the next regular inspection, and during the regular inspection, the identified abnormal AC line voltage detector can be quickly replaced, etc.

[0138] Although the third and fourth embodiments have been described as examples using a three-level converter, the present invention is not limited to this example and can be similarly applied to cases using a two-level converter.

[0139] The above-described embodiment includes the following items. However, the items included in the above-described embodiment are not limited to the following items.

[0140] (Item 1) A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between 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 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 estimation value, which is an estimation value of an AC 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 electric motor from the electric motor voltage estimation value; an adder that adds the correction value to a control command signal to generate the inverter output current command; A power conversion device having the following: According to this, an estimate of the AC line voltage of the motor is calculated from the inverter output voltage command and the DC voltage detection value, and a correction value for correcting the signal for controlling the motor is calculated from the estimate, making it possible to perform highly accurate correction control without using an AC line voltage detector.

[0141] (Item 2) The power conversion device is capable of switching between a plurality of modulation methods, The motor voltage calculator calculates the motor voltage estimation value using a calculation method corresponding to a modulation method of the power conversion device. Item 1. A power conversion device as described in item 1. This makes it possible to realize a power conversion device that can switch between a plurality of modulation methods depending on the application, etc.

[0142] (Item 3) the power converter is a three-level power converter; The plurality of modulation methods includes a dipolar modulation method, The motor voltage calculator includes: a pulse width calculator that calculates positive and negative pulse widths from the inverter output voltage command; a DC voltage fluctuation calculator that calculates a fluctuation amount of the DC voltage detection value with respect to a predetermined reference voltage; and a correction amount calculator that calculates a correction amount using the pulse width and the fluctuation amount. Equipped with When the dipolar modulation method is used, the correction amount is calculated using the pulse width calculator, the DC voltage fluctuation amount calculator, and the correction amount calculator, and the inverter output voltage command is corrected by the correction amount to calculate the motor voltage estimation value. Item 3. The power conversion device according to item 2. This allows for highly accurate control of the motor when a three-level dipolar modulation scheme is used.

[0143] (Item 4) the power converter is a three-level power converter; The plurality of modulation methods includes a unipolar modulation method, The motor voltage calculator includes: a DC voltage fluctuation ratio calculator that calculates a fluctuation ratio of the DC voltage detection value to a predetermined reference voltage, and a phase voltage calculator that calculates an AC phase voltage estimation value when the AC voltage command is positive and when the AC voltage command is negative, from an AC voltage command that is the inverter output voltage command and the fluctuation ratio, When the unipolar modulation method is used, the DC voltage fluctuation ratio calculator and the phase voltage calculator calculate the AC phase voltage estimation value, and output the AC phase voltage estimation value according to the polarity of the AC voltage command, thereby generating the motor voltage estimation value. Item 3. The power conversion device according to item 2. This allows for highly accurate control of the motor when a three-level unipolar modulation scheme is used.

[0144] (Item 5) The power converter is a two-level power converter; 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, Calculating the fluctuation ratio by the DC voltage fluctuation ratio calculator, and calculating the motor voltage estimated value from the AC voltage command, which is the inverter output voltage command, and the fluctuation ratio. Item 1. A power conversion device as described in item 1. This enables highly accurate control of the motor in a two-level modulation system.

[0145] (Item 6) A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between potentials to 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 detection value; a correction control unit that calculates a correction value for correcting a signal for controlling the electric motor from the detected electric motor voltage 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 detected 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 estimation value that is an estimation value of an AC line voltage of the motor from the inverter output voltage command and the DC voltage detection value; an AC line voltage detector abnormality determiner that determines an abnormality in the AC line voltage detector based on the motor voltage estimate value; A power conversion device having the following: According to this, an estimate of the AC line voltage of the motor is calculated from the inverter output voltage command and the DC voltage detection value, and an abnormality in the AC line voltage detector is determined based on the estimate, making it possible to detect an abnormality in the AC line voltage detector in a configuration that uses an AC line voltage detector.

[0146] (Item 7) the AC line voltage detector abnormality determiner determines that there is an abnormality in wiring connected to an AC line voltage detector whose output is equal to or lower than a predetermined threshold value; Item 7. The power conversion device according to item 6. According to this, in a configuration using an AC line voltage detector, it is further possible to detect an abnormality in the wiring connected to the AC line voltage detector.

[0147] (Item 8) and an abnormality-time calculation value switch 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 calculation unit to the correction control unit instead of the motor voltage detection value from the AC line voltage detector determined to be abnormal. Item 7. The power conversion device according to item 6. According to this, an abnormality in the AC line voltage detector is determined and the motor voltage detection value from the abnormal AC line voltage detector is switched to the motor voltage estimate value calculated by the motor voltage calculation unit. Therefore, in a configuration using an AC line voltage detector, it is possible to continue control of the motor normally even if the AC line voltage detector becomes abnormal.

[0148] (Item 9) when determining that an abnormality has occurred in the AC line voltage detector, the AC line voltage detector abnormality determiner causes a display device to display information about the abnormality. Item 9. The power conversion device according to any one of items 6 to 8. According to this, when an abnormality is determined in the AC line voltage detector, information regarding the abnormality is displayed, making it possible to easily know the abnormality of the AC line voltage detector in a configuration that uses an AC line voltage detector.

[0149] (Item 10) A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between potentials to which the smoothing capacitor is connected as a DC voltage detection value; A method for controlling an electric motor using a power conversion device comprising: 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 an inverter output current command; calculating a motor voltage estimate value, which is an estimate value of an AC line voltage of the motor, from the inverter output voltage command and the DC voltage detection value; calculating a correction value for correcting a signal for controlling the motor from the motor voltage estimate value; adding the correction value to a control command signal to generate the inverter output current command; Electric motor control method.

[0150] (Item 11) A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between potentials to 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 detection value; An abnormality detection method for detecting an abnormality in a power conversion device comprising: calculating a correction value for correcting a signal for controlling the electric motor from the detected electric motor voltage value; adding the correction value to 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; calculating an estimated motor voltage value, which is an estimated value of an AC line voltage of the motor, from the inverter output voltage command and the detected DC voltage value; determining whether or not the AC line voltage detector is abnormal based on the estimated motor voltage value; Anomaly detection methods. [Explanation of symbols]

[0151] 1...AC power supply, 2...converter unit, 3...inverter unit, 4...electric motor, 5...converter control device, 6...inverter control device, 7...current detector, 8...speed detector, 9...current detector, 10...AC 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, 6 3...current controller, 64...pulse generator, 65...neutral point voltage controller, 66...excitation current command generator, 67...magnetic flux controller, 68...compensation controller, 69...adder, 70...3-level motor voltage calculator, 71...3-level dipolar modulation voltage calculator, 72...3-level unipolar modulation voltage calculator, 73...compensation calculation selection unit, 74...AC line voltage calculator, 80...2-level motor voltage calculator, 81...2-level modulation voltage calculator, 82...AC line voltage calculator, 90...AC line voltage detector abnormality judgment device, 91... display device, 92... abnormality-time calculation value switch, 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 fluctuation amount calculator, 713... correction amount calculator, 714... dipolar motor phase voltage calculator, 721... DC voltage fluctuation ratio calculator, 722... phase voltage calculator, 723... unipolar motor phase voltage calculator, 811... DC voltage fluctuation ratio calculator, 812... phase voltage calculator

Claims

1. A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between 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 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 estimation value, which is an estimation value of an AC 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 control command signal for controlling the electric motor from the electric motor voltage estimation value; an adder that adds the correction value to the control command signal to generate the inverter output current command; A power conversion device having the following:

2. The power conversion device is capable of switching between a plurality of modulation methods, The motor voltage calculator calculates the motor voltage estimation value using a calculation method corresponding to a modulation method of the power conversion device. The power conversion device according to claim 1 .

3. the power converter is a three-level power converter; The plurality of modulation methods includes a dipolar modulation method, The motor voltage calculator includes: a pulse width calculator that calculates positive and negative pulse widths from the inverter output voltage command; a DC voltage fluctuation calculator that calculates a fluctuation amount of the DC voltage detection value with respect to a predetermined reference voltage; and a correction amount calculator that calculates a correction amount using the pulse width and the fluctuation amount. Equipped with When the dipolar modulation method is used, the correction amount is calculated using the pulse width calculator, the DC voltage fluctuation amount calculator, and the correction amount calculator, and the inverter output voltage command is corrected by the correction amount to calculate the motor voltage estimation value. The power conversion device according to claim 2 .

4. the power converter is a three-level power converter; The plurality of modulation methods includes a unipolar modulation method, The motor voltage calculator includes: a DC voltage fluctuation ratio calculator that calculates a fluctuation ratio of the DC voltage detection value to a predetermined reference voltage, and a phase voltage calculator that calculates an AC phase voltage estimation value when the AC voltage command is positive and when the AC voltage command is negative, from an AC voltage command that is the inverter output voltage command and the fluctuation ratio, When the unipolar modulation method is used, the DC voltage fluctuation ratio calculator and the phase voltage calculator calculate the AC phase voltage estimation value, and output the AC phase voltage estimation value according to the polarity of the AC voltage command, thereby generating the motor voltage estimation value. The power conversion device according to claim 2 .

5. the power converter is a two-level power converter; 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, Calculating the fluctuation ratio by the DC voltage fluctuation ratio calculator, and calculating the motor voltage estimated value from the AC voltage command, which is the inverter output voltage command, and the fluctuation ratio. The power conversion device according to claim 1 .

6. A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between potentials to 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 detection value; a correction control unit that calculates a correction value for correcting a control command signal for controlling the electric motor from the detected electric motor voltage value; an adder that adds the correction value to the control command signal to generate an inverter output current command; a current detector that detects an output current of the inverter and outputs the detected 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 estimation value, which is an estimation value of an AC line voltage of the motor, from the inverter output voltage command and the DC voltage detection value; an AC line voltage detector abnormality determiner that determines an abnormality in the AC line voltage detector based on the motor voltage estimate value; A power conversion device having the following:

7. the AC line voltage detector abnormality determiner determines that there is an abnormality in wiring connected to an AC line voltage detector whose output is equal to or lower than a predetermined threshold value; The power converter according to claim 6.

8. and an abnormality-time calculation value switch 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 calculation unit to the correction control unit instead of the motor voltage detection value from the AC line voltage detector determined to be abnormal. The power converter according to claim 6.

9. when determining that an abnormality has occurred in the AC line voltage detector, the AC line voltage detector abnormality determiner causes a display device to display information about the abnormality. The power conversion device according to any one of claims 6 to 8.

10. A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between potentials to which the smoothing capacitor is connected as a DC voltage detection value; A method for controlling an electric motor using a power conversion device comprising: 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 an inverter output current command; calculating a motor voltage estimate value, which is an estimate value of an AC line voltage of the motor, from the inverter output voltage command and the DC voltage detection value; calculating a correction value for correcting a control command signal for controlling the motor from the motor voltage estimation value; adding the correction value to the control command signal to generate the inverter output current command; Electric motor control method.

11. A converter that converts an AC input into a plurality of potentials; an inverter for converting the voltages of the plurality of potentials into an AC output for an electric motor; a smoothing capacitor connected between two of the plurality of potentials to suppress potential fluctuation between the potentials; a DC voltage detector that detects a potential difference between potentials to 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 detection value; An abnormality detection method for detecting an abnormality in a power conversion device comprising: calculating a correction value for correcting a control command signal for controlling the electric motor from the detected electric motor voltage 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 such that the inverter output current coincides with the inverter output current command; calculating an estimated motor voltage value, which is an estimated value of an AC line voltage of the motor, from the inverter output voltage command and the detected DC voltage value; determining whether the AC line voltage detector is abnormal based on the estimated motor voltage value; Anomaly detection methods.

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