JP6636216B2 - AC motor control device - Google Patents

Description

  The present application relates to a control device for controlling an AC motor, and more particularly to an output voltage control of a power converter that drives the AC motor.

  In a power converter for driving an AC motor, particularly an inverter using PWM (Pulse-Width Modulation), switching elements of two arms perform a switching operation based on a voltage command to generate an AC voltage and output the AC voltage to an AC load. I do. At this time, a dead time (Td), which is a period during which the switching elements of the two arms are simultaneously turned off, is provided for the purpose of preventing short-circuit destruction due to simultaneous conduction of the switching elements of the two arms. Due to this dead time, a distortion occurs in the output voltage of the inverter, torque torque occurs in the AC motor driven by the inverter, and control accuracy of the AC motor deteriorates.

For this reason, conventionally, a method is known in which a compensation signal calculated based on the output current of the power converter is added to a voltage command of the power converter to suppress output voltage distortion.
In the following conventional technique, output voltage distortion is estimated based on an output voltage command value and an output current value of a power converter, and the amplitude of a compensation signal is adjusted based on the estimated value (for example, see Patent Document 1). .
It is also disclosed that a direction orthogonal to the induced voltage of the load is obtained, and the output voltage command value is corrected based on the value of the estimated output voltage error in the direction orthogonal to the induced voltage and the output current value ( For example, see Patent Document 2).

Japanese Patent No. 3536114 Japanese Patent No. 4448351

  In the power converter, a delay time occurs in switching due to the influence of the parasitic capacitance of the switching element and the impedance in the wiring. For this reason, the voltage error, which is the output voltage distortion generated due to the dead time, also changes from a rectangular wave shape. In the above-mentioned conventional method, the magnitude of the voltage error is suppressed, but a spike-shaped voltage error sometimes remains near the zero cross phase of the current.

  The present application discloses a technique for solving the above-described problem. In a control device for an AC motor, by appropriately generating a voltage command for a power converter, a current near a 0 cross phase is obtained. An object of the present invention is to prevent spike-shaped voltage errors from occurring and to suppress output voltage errors with high accuracy.

  A control device for an AC motor disclosed in the present application generates a voltage command for a power converter that drives the AC motor, controls the AC motor, and detects a phase current of each phase of the AC motor. A correction unit that calculates a correction voltage for compensating an output voltage error of the power converter to correct the voltage command; and a voltage error feature value that extracts a feature value of the output voltage error based on the detected phase current. An extraction unit; and a correction voltage adjustment unit that adjusts a parameter of the correction voltage based on the extracted feature amount of the output voltage error. The correction voltage adjustment unit includes a first adjustment unit that adjusts, as the parameter, a parasitic capacitance in the power converter, which is a first parameter corresponding to a slope of the correction voltage, wherein the correction unit includes: The correction voltage is calculated using the parameter adjusted by the correction voltage adjustment unit.

  According to the control device for an AC motor disclosed in the present application, the parasitic capacitance in the power converter, which corresponds to the slope of the correction voltage for compensating the output voltage error of the power converter, is adjusted near the zero cross phase of the current. This prevents the occurrence of a spike-like output voltage error in the above, and suppresses the output voltage error with high accuracy.

FIG. 2 is a functional block diagram showing a configuration of a control device for the AC motor according to the first embodiment. FIG. 2 is a diagram illustrating a hardware configuration of a control device for the AC motor according to the first embodiment. FIG. 4 is a waveform diagram illustrating an output voltage error of the power converter. FIG. 4 is a waveform diagram of an output current and an error voltage of the power converter. FIG. 3 is a control block diagram illustrating a voltage error feature amount extraction unit according to the first embodiment. FIG. 3 is a control block diagram illustrating a correction voltage adjustment unit according to the first embodiment. FIG. 5 is a diagram illustrating a switching operation of the inverter according to the first embodiment. FIG. 5 is a diagram illustrating a switching operation of the inverter according to the first embodiment. FIG. 3 is a waveform chart of each part of the inverter according to the first embodiment. It is the elements on larger scale of FIG. FIG. 5 is a waveform chart showing a component orthogonal to a current vector of an output voltage error according to the first embodiment. FIG. 5 is a diagram illustrating an operation of a correction voltage adjustment unit according to the first embodiment. FIG. 5 is a diagram illustrating an operation of a correction voltage adjustment unit according to the first embodiment. FIG. 13 is a functional block diagram illustrating a configuration of a control device for an AC motor according to a third embodiment. FIG. 13 is a block diagram illustrating an operation in a parameter adjustment mode in the control device for the AC motor according to the third embodiment. FIG. 13 is a block diagram illustrating an operation in a normal mode in the control device for the AC motor according to the third embodiment. FIG. 14 is a functional block diagram illustrating a configuration of a control device for an AC motor according to a fourth embodiment. FIG. 14 is a control block diagram illustrating a correction voltage adjustment unit according to a fourth embodiment.

Embodiment 1 FIG.
Hereinafter, a control device for an AC motor according to the first embodiment will be described with reference to the drawings.
FIG. 1 is a functional block diagram showing a configuration of the control device for an AC motor according to the first embodiment. As shown in FIG. 1, the control device 10 of the AC motor 1 controls the driving of the AC motor 1 by controlling a PWM inverter which is a power converter 3 having a switching element.
The control device 10 includes a power converter 3, a phase current detector 4 as a phase current detector, a voltage error characteristic amount extraction unit 100, a correction unit 220 including a correction voltage calculation unit 200 and an adder 210, And a voltage adjusting unit 300. The AC motor 1 includes a phase detector 2.

  In this case, the control device 10 includes the power converter 3, but the power converter 3 may be arranged outside the control device 10 and controlled by the control device 10. Also, the phase current detector 4 may be arranged outside the control device 10. In this case, the current detection unit in the control device 10 controls the phase current of each phase based on the current signal from the phase current detector 4. iuvw is detected.

The control device 10 shown in FIG. 1 can be realized, for example, by a hardware configuration as shown in FIG. As shown in FIG. 2, the control device 10 includes a power converter 3, a phase current detector 4, a processor 12, and a storage device 13. Then, the processor 12 inputs the three-phase voltage command Vuvw * from the higher-level control device 11, reads out the program stored in the storage device 13, and executes the program. The functions of the voltage error characteristic amount extraction unit 100, the correction unit 220, and the correction voltage adjustment unit 300 in FIG. 1 are realized by executing a program on the processor 12.
Note that the plurality of processors 12 and the plurality of storage devices 13 may execute the above functions in cooperation with each other.

As described above, in the power converter 3, switching control is performed by providing a dead time, which is a period in which the switching elements of the two arms are simultaneously turned off, and a disturbance voltage is generated in the output voltage by the dead time. It becomes a voltage error with respect to the voltage command.
FIG. 3 is a waveform diagram for one cycle of the U-phase for explaining the output voltage error of the power converter 3.
The Td disturbance voltage P due to the dead time is determined from the dead time period Td, the carrier frequency fc, and the DC voltage Vdc of the power converter 3, has a small area of (Td · Vdc), and has the U-phase current iu This is a pulse voltage generated in the reverse polarity fc times in a half cycle.

The Td disturbance voltage P of each phase is a rectangular wave-shaped error voltage having an amplitude of VTd = Td.fc.Vdc and having a polarity opposite to the polarity of the phase current [i] output from the power converter 3, assuming a time average. It turns out that it is equivalent to Q. The symbol [] indicates that the quantity in [] is a vector.
Assuming that the switching operation is performed ideally without delay, the rectangular wave error voltage Q can be expressed by (−sgn ([i]) · VTd). In this case, a correction voltage R having a polarity opposite to that of the error voltage Q, that is, a rectangular wave voltage having the same polarity as the phase current and having an amplitude of VTd is added in advance to each phase of the voltage command input to the power converter 3. This makes it possible to correct the Td disturbance voltage. The correction voltage R having a rectangular waveform is represented by (sgn ([i]). VTd).

  However, actually, the switching ON / OFF time occurs due to the influence of the parasitic capacitance of the switching element and the impedance in the wiring. As shown in FIG. 4, the actual Td disturbance voltage (error voltage) affected by these influences has a rectangular wave-like angle, and has a slope in a minute phase section sandwiching the zero cross phase where the current passes through zero. It has a smooth trapezoidal wavy shape.

  In the control device 10, a correction voltage Vuvwc of each phase for compensating an output voltage error (hereinafter, a voltage error or an error voltage) with respect to the voltage command Vuvw * of each phase given from the higher-level control device 11 is calculated by the correction voltage calculation unit 200 The adder 210 adds the correction voltage Vuvwc to the voltage command Vuvw *, and outputs the corrected voltage command 3a to the power converter 3. Power converter 3 drives AC motor 1 under output control based on corrected voltage command 3a. Then, the current iuvw of each phase flowing through the AC motor 1 is detected by the phase current detector 4. At this time, the two-phase current may be detected and the remaining one-phase current may be calculated and obtained.

  The voltage error feature value extraction unit 100 extracts the voltage error feature value Vqi as follows. First, based on the detected phase current iuvw and the phase θre from the phase detector 2, a current vector phase θi is calculated after conversion into a dq-axis current on a rotating magnetic field. Then, a current vector and a voltage component Vdqi (Vdi, Vqi) in the orthogonal direction thereof are calculated from the phase current iuvw using the current vector phase θi. The orthogonal voltage component Vqi of the calculated current vector is a feature amount of the voltage error. Further, the voltage error feature quantity extraction unit 100 calculates the reproduced phase current iuvwRP based on the phase current iuvw and the current vector phase θi.

The correction voltage adjustment unit 300 receives the current vector phase θi and the voltage error characteristic amount Vqi from the voltage error characteristic amount extraction unit 100, and receives the correction voltage Vuvwc from the correction voltage calculation unit 200. Then, the parasitic capacitance C as a first parameter corresponding to the slope of the correction voltage Vuvwc and the amplitude α of the correction voltage Vuvwc are adjusted and output as a second parameter.
The correction voltage calculation unit 200 calculates the correction voltage Vuvwc for each phase based on the reproduced phase current iuvwRP, the amplitude α, and the parasitic capacitance C.

Next, details of the operation of the voltage error characteristic amount extraction unit 100 will be described below with reference to FIG. Note that the configuration shown in FIG. 5 is an example, and the configuration is not limited to this.
As shown in FIG. 5, the detected phase current iuvw is converted by a coordinate converter (three-phase-dq converter) 101 into a dq-axis current idq (id, iq) on the rotational coordinates based on the phase θre. .
The dq-axis current idq is filtered by a low-pass filter (LPF) 102 and then input to a current vector phase calculator 103. The current vector phase calculator 103 obtains the current vector phase θi by obtaining the arc tangent of the filtered dq-axis current idq and adding it to the phase θre.

The dq-axis current idq is also input to the amplitude calculator 104, and the amplitude calculator 104 calculates the phase current amplitude in (= √ ((2/3) · (id ² + iq ² ))). Then, the phase current calculator 105 calculates a reproduced phase current iuvwRP (iuRP, ivRP, iwRP) based on the current vector phase θi from the amplitude in and the current vector phase θi by the following equation (1).

  Further, the phase current iuvw is converted into a dqi-axis current idqi (idi, iqi) by a coordinate converter (three-phase-dqi converter) 106 that converts the current vector phase θi into dqi coordinates that are coordinates synchronized with the current vector phase θi. Then, the motor inverse model calculator 107 that obtains a voltage from a current according to the voltage equation of the AC motor 1 obtains a dqi-axis voltage Vdqi (Vdi, Vqi) from a dqi-axis current idqi by the following equation (2). The voltage component Vqi in the orthogonal direction of the current vector is a feature value of the voltage error.

  Here, R is a winding resistance of the AC motor 1, Ld and Lq are dq-axis inductances of the AC motor 1, and p is a differential operator. Regarding the differential operation, there are a number of known techniques, such as mounting as a pseudo-differential operation in combination with a low-pass filter, and these can be used.

Next, details of the operation of the correction voltage adjustment unit 300 will be described below with reference to FIG. Note that the configuration shown in FIG. 6 is an example, and the configuration is not limited to this.
As shown in FIG. 6, the correction voltage adjustment unit 300 converts the correction voltage Vuvwc into a dqi-axis voltage Vdqic by a coordinate converter (three-phase-dqi converter) 301 that converts the current vector phase θi into dqi coordinates. To obtain the orthogonal voltage component Vqic of the current vector. The multiplier 302 multiplies the qi-axis voltage Vqic by the voltage error characteristic amount Vqi, which is also a voltage component in the orthogonal direction of the current vector, to obtain a multiplication result 302a.

  The multiplication result 302a is input to a parasitic capacitance adjuster 303 as a first adjuster and an amplitude adjuster 304 as a second adjuster. The parasitic capacitance adjuster 303 adjusts the parasitic capacitance C corresponding to the slope of the correction voltage Vuvwc, and the amplitude adjuster 304 adjusts the amplitude α of the correction voltage Vuvwc. The parasitic capacitance adjuster 303 adjusts the parasitic capacitance C by multiplying the multiplication result 302a by a predetermined gain K1 and performing integration adjustment only in a predetermined section. The amplitude adjuster 304 adjusts the amplitude α by multiplying the multiplication result 302a by a predetermined gain (−K2: K2> 0) and performing integral adjustment. The details of the adjustment of the amplitude α and the parasitic capacitance C will be described later.

As described above, the correction voltage calculation unit 200 calculates the correction voltage Vuvwc for each phase based on the reproduced phase current iuvwRP, the amplitude α, and the parasitic capacitance C. The principle will be described below.
The power converter 3 is configured by a three-phase PWM inverter, and the switching operation of the inverter for one phase will be described with reference to FIGS. FIG. 7 is a circuit diagram of the inverter 20 for one phase including the parasitic capacitances C1 and C2 (C1 = C2 = C). The inverter 20 for one phase is configured by connecting a leg in which two switching elements S1 and S2 each having a diode connected in anti-parallel to each other in series are connected in parallel to a DC power supply 21 having a voltage Vdc. A connection point between the two switching elements S1 and S2 serves as an AC output terminal, and the switching elements S1 and S2 have parasitic capacitances C1 and C2 in parallel.

For the sake of simplicity, consider the case where the current i is positive. In the model of the inverter 20 including the parasitic capacitances C1 and C2, for example, the following operation is performed at the timing when the switching element S2 is turned off and the switching element S1 is turned on. That is, as shown in FIG. 8, even when the switching element S1 is turned on, the voltage does not rise to the power supply voltage Vdc until the charging of the parasitic capacitance C1 is completed. The voltage does not become 0 until the discharge is completed. The behavior of the output voltage at this time will be described with reference to FIG.
As shown in FIG. 9, a P command VP as a voltage command to the positive switching element S1 and an N command VN as a voltage command to the negative switching element S2 are provided with a dead time Td. In this case, an output voltage like the ideal output voltage Vout-a is ideally obtained. However, the output voltage has a delay time Tdr of the rising timing and a delay time Tdf of the falling timing. Further, there is a voltage Vr (i) from when the voltage actually starts rising until the parasitic capacitance C is completely charged, and a voltage Vf (i) from when the voltage starts falling until the parasitic capacitance C is completely discharged. Considering these, the actual output voltage has a voltage waveform like the output voltage Vout-b.

The delay times Tdr and Tdf between the rise and fall of the output voltage are different, and the voltages Vr (i) and Vf (i) are also different. The voltage Vr (i) and the voltage Vf (i) often vary in a complicated manner depending on the current, and it is difficult to accurately formulate them.
Therefore, the total amount of Vr (i) + Vf (i) is considered without individually considering the voltages Vr (i) and Vf (i). That is, the charge / discharge voltage Vp (i) = Vr (i) + Vf (i), and an output voltage model (output voltage Vout-md) in which charging is completed instantaneously and discharged linearly at a constant current i / 2. Think.
At this time, Vp (i) is represented by the area S of the triangle shown in FIG.
Discharge time t1 = (C · Vdc) / ([i] / 2)
And
S = Vdc · t1 · (１ ／) = (C · Vdc ² ) / [i]
Becomes

Since such a triangle having the area S appears at the carrier frequency fc in a half cycle, Vp (i) is expressed by the following equation (3).
Vp (i) = C · Vdc ² · fc / [i] (3)

The voltage error of the output voltage is considered in two situations, that is, when the discharge time t1 is equal to or less than the dead time Td and when the discharge time t1 is longer than the dead time Td.
First, the discharge time t1 is equal to or less than the dead time Td, ie,
In the case of (C · Vdc) / ([i] / 2) ≦ Td,
The voltage error is the sum of the error voltage Q shown in FIG. 3 and Vp (i) according to the above equation (3). Since there are also voltage errors due to the delay times Tdr and Tdf between the rise time and the fall time, when the amplitude α is introduced as a parameter for adaptively adjusting these, the voltage error Vuvwer is calculated by the following equation (4). expressed.
[Vuvwer]
= Α (Td · fc · Vdc · (−sgn ([i])) + C · Vdc ² · fc / [i])
... (4)

Next, the discharge time t1 is longer than the dead time Td, ie,
When (C · Vdc) / ([i] / 2)> Td,
Although the triangle of Vp (i) does not fit in the dead time Td section and is partially truncated, it is difficult to formulate. Therefore, a voltage error Vuvwer that can be smoothly switched from the voltage error represented by the above equation (4) is set.

Since the correction voltage Vuvwc for compensating for the voltage error Vuvwer is obtained by inverting the polarity of the voltage error, the correction voltage Vuvwc is obtained by the following equation (5).
[Vuvwc]
(│ [i] │ ≧ ith) = α (Td · fc · Vdc · sgn ([i]) − C · Vdc ² · fc / [i])
(When | [i] | <it) = α (Td ² · fc / 4C) · [i])
Where is = 2C · Vdc / Td
... (5)

  As described above, the correction voltage calculation unit 200 calculates the correction voltage Vuvwc of each phase using the above equation (5) based on [i], which is the reproduced phase current iuvwRP, and the amplitude α and the parasitic capacitance C. I do.

Next, adjustment of the amplitude α and the parasitic capacitance C by the correction voltage adjustment unit 300 will be described below with reference to FIGS.
As described above, the actual Td disturbance voltage is a smooth trapezoidal wave having a rectangular wave-like corner and a slope in a minute phase section sandwiching the zero cross phase where the current passes through zero ( (See FIG. 4). Assuming that the voltage output to the AC motor 1 cannot be completely corrected and a voltage error remains, if the output voltage is subjected to rotational coordinate conversion in a direction orthogonal to the direction synchronized with the current vector phase θi as shown in FIG. As shown in (1), the voltage component Vqi in the current vector orthogonal direction (qi direction) is not a zero but a sawtooth waveform. If the sawtooth-shaped qi-axis voltage component Vqi is close to 0, there is almost no residual voltage error, and it can be determined that the voltage error due to the dead time Td has been accurately corrected.

Therefore, as shown in FIGS. 12 and 13, the signal processing of the Fourier analysis is applied to correct the qi-axis voltage Vqi, which is the characteristic amount of the voltage error, as the target signal and the signal synchronized with the residual voltage error as the base signal. The qi-axis voltage Vqic of the voltage Vuvwc is set. Then, the residual voltage error component included in the qi-axis voltage Vqi is extracted to cancel the residual voltage error.
As shown in FIG. 12, the excess or deficiency of the amplitude α, which is a parameter of the correction voltage Vuvwc, appears in the amplitude itself including the polarity of Vqi. Therefore, α can be obtained by integrating the multiplication result 302 a by the multiplier 302 with the amplitude adjuster 304. A loop is formed to feed back this α to the correction voltage calculation unit 200. Since the integral adjustment gain (−K2) of the amplitude adjuster 304 is negative, α is adjusted so as to reduce the residual voltage error. When the residual voltage error disappears, α does not change.

  Further, the parasitic capacitance C is a parameter relating to the slope of the correction voltage Vuvwc, and the excess or deficiency appears in the slope of Vqi in the 0 cross section (section sandwiching the 0 cross point) as shown in FIG. The zero cross point of Vqi is a zero cross point of a three-phase current that appears six times in one cycle of the electrical angle. That is, the slope of the zero cross section of Vqi is the slope of the zero cross section of Vqi in the phase section sandwiching the zero current cross phase.

  Therefore, C can be obtained by integrating the multiplication result 302a of the multiplier 302 by the parasitic capacitance adjuster 303 in a predetermined phase section Ti sandwiching the current 0 cross phase. The phase section Ti is a phase section in which the inclination near the current 0 cross phase is reflected, and as shown in FIG. 13, is a phase section in which the time change rate of Vqi is steeper. In this case, the smaller phase section of the peak-to-peak is selected as the phase section Ti. Then, the parasitic capacitance adjuster 303 may be operated in the phase section Ti.

Further, it is not necessary to select all of the peak-to-peak section as the phase section, and in order to prevent malfunction, a phase section from half of one peak value to half of the other peak value, or one of the peak values A phase section from 1/4 to 1/4 of the other peak value may be used. Then, it is set to operate the parasitic capacitance adjuster 303 in the selected phase section.
C adjusted by multiplying the integration result by the gain K1 is fed back to the correction voltage calculation unit 200. Since the amplitude α is adjusted so as to reduce the residual voltage error, the adjustment of the parasitic capacitance C is performed so as to operate with an appropriate response.

In this way, the amplitude α of the correction voltage Vuvwc is adjusted so as to cancel the residual voltage error, and the slope of the correction voltage Vuvwc is adjusted by adjusting the parasitic capacitance C that divides the integration section. Thereby, the slope of the correction voltage Vuvwc is adjusted so as to match the slope of the Td disturbance voltage in a minute phase section sandwiching the current 0 cross phase.
As described above, the Td disturbance voltage to be corrected has a smooth trapezoidal waveform as shown in FIG. 4, and the correction voltage to be generated has the same shape. In this embodiment, the slope and amplitude of the correction voltage Vuvwc can be individually adjusted. Therefore, the trapezoidal waveform can be adjusted more accurately, the occurrence of a spike-like output voltage error near the current 0 cross phase can be prevented, and the output voltage error can be suppressed with high accuracy.

Embodiment 2 FIG.
Next, a control device for an AC motor according to the second embodiment will be described.
In the first embodiment, the correction voltage calculation unit 200 calculates the correction voltage Vuvwc for each phase using the above equation (5) based on [i], which is the reproduced phase current iuvwRP, and the amplitude α and the parasitic capacitance C. In the second embodiment, the correction voltage Vuvwc is obtained by another calculation. Other configurations are the same as those in the first embodiment.

As described above, the output voltage of the inverter includes the delay times Tdr and Tdf between the rising time and the falling time, and the voltages Vr (i) and Vf (i) until the charging and discharging of the parasitic capacitance C is completed. (See FIG. 9). In this case, the output voltage is a rectangular wave component as an output voltage model.
(Td · fc · Vdc + (Tdr−Tdf) · fc · Vdc)
= (Td + Tdr-Tdf) · fc · Vdc
And Vp (i) represented by the above equation (3), which is the remaining component.

Assuming that the amplitude α is a parameter for adjusting only the rectangular wave component, the correction voltage Vuvwc can be given by the following equation (6).
[Vuvwc]
= Α · Td · fc · Vdc · sgn ([i]) − C · Vdc ² · fc / ([i] + ix)
... (6)
Here, ix is a correction term that sets the correction voltage Vuvwc to 0 when the current i is 0, and is defined as follows.
ix = C · Vdc / (α · Td)

By using the following equation (7) for the correction voltage Vuvwc, the polarity can be changed with the same absolute value according to the current sign.
[Vuvwc]
When (| [i] | ≧ 0) = α · Td · fc · Vdc · sgn ([i]) − C · Vdc ² · fc / ([i] + ix)
When (| [i] | <0) = α · Td · fc · Vdc · sgn ([i]) − C · Vdc ² · fc / ([i] −ix)
Where ix = C · Vdc / (α · Td)
... (7)

  In this embodiment, the calculation load for calculating the correction voltage Vuvwc is larger than in the first embodiment. However, since the amplitude α is a parameter for adjusting only the rectangular wave component, the correction voltage Vuvwc is obtained with high accuracy. The output voltage error can be suppressed with higher accuracy.

Embodiment 3 FIG.
Next, a control device for an AC motor according to the third embodiment will be described. FIG. 14 is a functional block diagram showing a configuration of the control device for an AC motor according to the third embodiment.
The control device 10A operates in two operation modes: a normal mode and a parameter adjustment mode. The control device 10A includes a power converter 3, a phase current detector 4, a voltage error feature amount extraction unit 100, A correction unit 220 including a voltage calculation unit 200 and an adder 210, a correction voltage adjustment unit 300A, a parameter acquisition command generator 400, a command switch 410, and a parameter storage unit 500 are provided. Further, the control device 10A has a sequence for shifting to the normal mode after performing the operation in the parameter adjustment mode.
Configurations and operations other than the correction voltage adjustment unit 300A, the parameter acquisition command generator 400, the command switch 410, and the parameter storage unit 500 are the same as those in the first embodiment.

  The hardware configuration in the third embodiment is the same as that shown in FIG. In this case, the functions of the voltage error characteristic amount extraction unit 100, the correction unit 220, the correction voltage adjustment unit 300A, the parameter acquisition command generator 400, the command switch 410, and the parameter storage unit 500 are read from the storage device 13. The program is realized by being executed on the processor 12.

FIG. 15 is a block diagram illustrating the operation of the control device 10A in the parameter adjustment mode, and FIG. 16 is a block diagram illustrating the operation of the control device 10A in the normal mode.
In the parameter adjustment mode, the command switch 410 selects the voltage command Vuvw ** output from the parameter acquisition command generator 400. The parameter acquisition command generator 400 stores a control pattern of the AC motor 1 for determining the amplitude α and the parasitic capacitance C, which are the parameters of the correction voltage Vuvwc, and a voltage command Vuvw ** capable of realizing the control pattern. Is generated and output.
Then, as shown in FIG. 15, the voltage error characteristic amount extraction unit 100, the correction unit 220, and the correction voltage adjustment unit 300A adjust and correct the amplitude α and the parasitic capacitance C by the same operation as in the first embodiment. The voltage command Vuvw ** is corrected by calculating the voltage Vuvwc. At this time, the amplitude α and the parasitic capacitance C output from the correction voltage adjustment unit 300A are also input and stored in the parameter storage unit 500.

Thereafter, when the parameters α and the parasitic capacitance C converge, the mode shifts from the parameter adjustment mode to the normal mode. In the normal mode, the command switch 410 selects the externally supplied voltage command Vuvw *, and the correction voltage adjustment unit 300A and the parameter acquisition command generator 400 stop functioning.
Then, as shown in FIG. 16, the parameter storage unit 500 outputs the amplitude α and the parasitic capacitance C converged by the adjustment in the parameter adjustment mode to the correction voltage calculation unit 200. The correction voltage calculation unit 200 calculates the correction voltage Vuvwc of each phase based on the reproduced phase current iuvwRP, the amplitude α, and the parasitic capacitance C, as in the first embodiment, and the correction voltage Vuvwc is a voltage command Vuvw *. Is added to

  As described above, in the third embodiment, the control device 10A is configured to operate with the two types of operation modes of the normal mode and the parameter adjustment mode. Therefore, in the normal mode, the calculation of the parameter adjustment is unnecessary. become. Therefore, the same effect as in the first embodiment can be obtained, and the calculation load can be reduced.

  Also in this embodiment, the correction voltage Vuvwc may be calculated by applying the second embodiment, and the same effect is obtained.

Embodiment 4 FIG.
Next, a control device for an AC motor according to the fourth embodiment will be described.
FIG. 17 is a functional block diagram showing the configuration of the control device for an AC motor according to the fourth embodiment, and FIG. 18 is a control block diagram showing a correction voltage adjusting unit in the control device.
In the control device 10B according to this embodiment, the correction voltage adjustment unit 300B adjusts only the parasitic capacitance C as a parameter of the correction voltage Vuvwc. The correction voltage calculation unit 200 acquires the parasitic capacitance C from the correction voltage adjustment unit 300B, and uses the amplitude setting value that is a preset value for the amplitude α to calculate the reproduction phase current iuvwRP, the amplitude α, the parasitic capacitance C Is used to calculate the correction voltage Vuvwc for each phase. Other configurations are the same as those in the first embodiment.
Also, the hardware configuration in the fourth embodiment is the same as that shown in FIG.

As shown in FIG. 18, the correction voltage adjustment unit 300B receives the current vector phase θi and the voltage error characteristic amount Vqi from the voltage error characteristic amount extraction unit 100, and outputs the correction voltage Vuvwc from the correction voltage calculation unit 200. Is entered. The coordinate converter (three-phase-dqi converter) 301 converts the correction voltage Vuvwc into a dqi-axis voltage Vdqic to obtain the orthogonal voltage component Vqic of the current vector. The multiplier 302 multiplies the qi-axis voltage Vqic by the voltage error characteristic amount Vqi, which is also a voltage component in the orthogonal direction of the current vector, to obtain a multiplication result 302a.
The multiplication result 302a is input to the parasitic capacitance adjuster 303, and the parasitic capacitance adjuster 303 adjusts the parasitic capacitance C corresponding to the slope of the correction voltage Vuvwc. The parasitic capacitance adjuster 303 adjusts the parasitic capacitance C by integrating the multiplication result 302a for a predetermined phase section Ti sandwiching the current 0 cross phase and multiplying by a predetermined gain K1.
The method of adjusting the parasitic capacitance C is the same as in the first embodiment.

  As described above, the slope of the correction voltage Vuvwc is adjusted by adjusting the parasitic capacitance C so as to cancel the residual voltage error. Thereby, the slope of the correction voltage Vuvwc is adjusted so as to match the slope of the Td disturbance voltage in a minute phase section sandwiching the current 0 cross phase. Therefore, generation of a spike-like output voltage error near the current 0 cross phase can be prevented, and the output voltage error can be suppressed with high accuracy. Further, since the amplitude set value is used without performing the adjustment calculation of the amplitude α, the calculation load can be reduced.

  Also in this embodiment, the third embodiment is applied to operate in two types of operation modes, a normal mode and a parameter adjustment mode, so that the calculation load can be further reduced. In this case, the parasitic capacitance C is adjusted in the parameter adjustment mode, and the adjusted parasitic capacitance C is used in the normal mode. As the amplitude α, the same amplitude set value is used in both operation modes.

Although this application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments may apply to particular embodiments. However, the present invention is not limited thereto, and can be applied to the embodiment alone or in various combinations.
Accordingly, innumerable modifications not illustrated are envisioned within the scope of the technology disclosed herein. For example, a case where at least one component is deformed, added or omitted, and a case where at least one component is extracted and combined with components of other embodiments are included.

  REFERENCE SIGNS LIST 1 AC motor, 3 power converter, 4 phase current detector, 10, 10A, 10B control device, 100 voltage error characteristic amount extraction unit, 101 coordinate converter, 102 low pass filter, 105 phase current calculator, 200 correction voltage calculation Unit, 220 correction unit, 300, 300A, 300B correction voltage adjustment unit, 303 parasitic capacitance adjustment unit, 304 amplitude adjustment unit, 100 parameter acquisition command generator, 410 command switcher, 500 parameter storage unit.

Claims (10)

In the control device that generates a voltage command of the power converter that drives the AC motor and controls the AC motor,
A current detection unit that detects a phase current of each phase of the AC motor,
A correction unit that calculates a correction voltage for compensating an output voltage error of the power converter and corrects the voltage command;
A voltage error feature amount extraction unit that extracts a feature amount of the output voltage error based on the detection phase current;
A correction voltage adjustment unit that adjusts a parameter of the correction voltage based on the extracted feature amount of the output voltage error,
The correction voltage adjustment unit has a first adjustment unit that adjusts a parasitic capacitance in the power converter, which is a first parameter corresponding to a slope of the correction voltage as the parameter,
The correction unit calculates the correction voltage using the parameter adjusted by the correction voltage adjustment unit,
Control device for AC motor. The first adjustment unit calculates and adjusts the first parameter in a phase section sandwiching the zero cross phase of the detection phase current.
The control device for an AC motor according to claim 1. The phase section is a phase section having a steeper time change rate among the peak to peak sections of the feature amount.
The control device for an AC motor according to claim 2. The correction unit calculates a correction voltage so as to compensate for the output voltage error, using a disturbance voltage resulting from a dead time of switching of the power converter as the output voltage error,
The control device for an AC motor according to any one of claims 1 to 3. The voltage error feature amount extraction unit,
Converting the detected phase current into a dq-axis current on a rotating magnetic field of the AC motor,
The dq-axis current is filtered to obtain a current vector phase,
Detecting the orthogonal current component of the current vector from the detected phase current based on the current vector phase, and calculating the orthogonal voltage component of the current vector as the feature amount based on the orthogonal current component;
The control device for an AC motor according to any one of claims 1 to 4. The voltage error feature quantity extraction unit further reproduces a phase current from the dq-axis current based on the current vector phase, and the correction unit calculates the correction voltage based on the reproduced phase current.
A control device for an AC motor according to claim 5. The correction voltage adjustment unit further includes a second adjustment unit that adjusts a second parameter corresponding to the amplitude of the correction voltage as the parameter,
The correction unit calculates the correction voltage using the first and second parameters adjusted by the correction voltage adjustment unit;
The control device for an AC motor according to any one of claims 1 to 6. The correction unit calculates the correction voltage using the first parameter adjusted by the correction voltage adjustment unit and an amplitude set value of the correction voltage.
The control device for an AC motor according to any one of claims 1 to 6. A storage unit for holding the above parameters is provided, and two operation modes of a normal mode and a parameter adjustment mode are provided,
In the parameter adjustment mode, the correction voltage adjustment unit adjusts the parameter and holds the adjusted parameter in the storage unit,
When the adjustment of the parameters is completed, the mode is switched from the parameter adjustment mode to the normal mode,
In the normal mode, the operation of the correction voltage adjustment unit is stopped, and the correction unit obtains the parameter from the storage unit and calculates the correction voltage.
The control device for an AC motor according to any one of claims 1 to 8. The power converter includes the power converter, the power converter outputs a voltage according to the voltage command to the AC motor to drive the AC motor,
The control device for an AC motor according to any one of claims 1 to 9.

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