JP4937766B2 - Voltage inverter control device - Google Patents

Description

  The present invention relates to a control device for a voltage-type inverter, and more specifically, when an electric motor is driven by a voltage-type inverter that outputs an AC voltage having a desired magnitude and frequency by turning on and off a semiconductor switching element, the output of the inverter The present invention relates to a control device for compensating for an error or distortion included in a voltage.

In a normal voltage type inverter, switching elements constituting upper and lower arms are alternately conducted to generate an AC voltage having a desired magnitude and frequency. However, as is well known, the switching element has an operation delay at the time of turn-off, and thereby a short-circuit prevention period (dead time) is provided in the switching pattern in order to prevent an arm short circuit due to the upper and lower arms being simultaneously turned on.
However, due to this dead time, the output voltage of the voltage type inverter has an error with respect to the output voltage command, and distortion of the output voltage due to this causes torque ripple when the motor is driven.

As described in Patent Document 1, as a conventional technique for compensating for the distortion of the output voltage due to the dead time described above, the output voltage distortion is estimated based on the output voltage command and output current of the inverter. A method for adjusting the amplitude (compensation amount) of a compensation signal added to an output voltage command based on an estimated value is known.
Hereinafter, this prior art will be described with reference to FIG.

In FIG. 2, 101 is a voltage type PWM (pulse width modulation) inverter that outputs a voltage proportional to the voltage command, and 102 is an electric motor driven by the inverter 101.
In the inverter 101, a block 101 a indicated by a broken line models that the output voltage distortion Δv due to the dead time described above occurs according to the polarity of the output current i detected by the current detection unit 110. .

Reference numeral 103 denotes an input of a d-axis voltage command v _d ^* in the magnetic flux axis direction of the electric motor 102 in the rotating magnetic field coordinate system, a q-axis voltage command v _q ^* and a phase reference signal θ ^* (= ω ^* t) orthogonal thereto. The coordinate transformation means for outputting the output voltage command v ^* of the stator coordinate system, 109 is the addition means for adding the output voltage command v ^* and the compensation signal Δv ^* from the compensation means 105 described later, and 106 is the output current i. Is converted into a d-axis current i _d and a q-axis current i _q in a rotating magnetic field coordinate system, 107 is a d-axis voltage command v _d ^* , a q-axis voltage command v _q ^* , a d-axis current _id and a q-axis Distortion component estimation means for estimating a voltage distortion component (compensation residual component) based on the current i _q , 108 is a compensation amount adjustment means for adjusting the compensation amount based on the estimated voltage distortion component and the output current i, and 108 a is a voltage Means for inverting polarity of distortion component, 108 b is a polarity detecting means for outputting a switching signal according to the polarity of the output current i, 108c is an integrating means for integrating the output of the distortion component estimating means 107 selected by the switching signal or its inverted output, and 105 is the output current i. Compensation means for outputting a compensation signal Δv ^* corresponding to the polarity to the adding means 109.

In the above configuration, the output voltage distortion Δv can be estimated by a model in which a distortion component acts on a path from the voltage command v _d ^* , v _q ^{* of} each axis to the output voltage of the inverter 101, and distortion component estimation means 107 estimates a voltage distortion component according to the principle of a disturbance observer using the d-axis voltage command v _d ^* , the q-axis voltage command v _q ^* , the d-axis current i _d and the q-axis current i _q . The compensation amount adjusting means 108 controls the compensation signal Δv ^* from the compensation means 105 so that the voltage distortion component approaches zero, and the addition means 109 adds it to the original output voltage command v ^*. The output voltage distortion Δv is minimized.

That is, by adding the compensation signal Δv ^* to the original output voltage command v ^* and performing feedforward control of the output voltage distortion Δv, the output voltage v is suppressed from being included by compensating for the output voltage distortion. ing. The amplitude of the compensation signal (compensation amount) has the largest compensation effect when it matches the amplitude of the voltage distortion component, and a compensation residual component is generated even if it is larger or smaller than that. Whether the compensation amount is excessive or insufficient is determined by 108, and the compensation amount is controlled to the optimum value via the compensation means 105 based on the determination result.

Japanese Patent No. 3536114 (paragraphs [0007] to [0012], FIG. 1 etc.)

In the above prior art, the voltage distortion component estimated by the distortion component estimation means 107 serving as a disturbance observer includes the back electromotive force (speed electromotive force) of the motor 102, so that the output voltage command is used using the estimated distortion component as it is. Can not compensate. For this reason, it is necessary to adjust the compensation amount using the compensation amount adjusting unit 108 and the compensation unit 105.
The compensation amount adjusting means 108 and the compensating means 105 determine overcompensation or undercompensation based on the waveform of the voltage distortion component by performing integration, a difference calculation of the integral value, etc., and compensating according to the discrimination result. Complicated processing of determining the amount is performed, which leads to complicated circuit configuration and increased calculation load.

  Furthermore, when the above-described conventional technique is applied to open loop control such as V / f constant control, the voltage of the d-axis component, which is the magnetic flux axial direction component of the motor, is also compensated. There was also a problem that the excitation current was not secured and the stability deteriorated.

  Therefore, the problem to be solved by the present invention is that the output voltage distortion of the inverter can be minimized without requiring a complicated circuit configuration and arithmetic processing, and the electric motor can be stabilized even in open loop control such as constant V / f control. An object of the present invention is to provide a control device for a drivable voltage type inverter.

In order to solve the above problems, a voltage type inverter control device according to claim 1 controls a voltage type inverter that drives an electric motor by outputting an AC voltage of a desired magnitude and frequency by turning on and off a semiconductor switching element. A voltage distortion component estimation means for sequentially estimating the output voltage distortion component of the inverter using the output voltage command and output current of the inverter, and a compensation means for compensating the output voltage of the inverter with the output voltage distortion component, In the control device of the voltage type inverter provided with
The voltage distortion component estimation means includes
A q-axis output voltage is estimated from a q-axis current detection value orthogonal to the magnetic flux axis of the motor obtained by converting the AC current detection value of the inverter, and the q-axis output voltage and the q-axis output voltage command are used. a first estimating means for estimating a q-axis disturbance voltage including q-axis output voltage error due to the inverter dead time, the counter electromotive force component of the electric motor, and the d-axis interference component orthogonal to the magnetic flux axis of the motor ,
Second estimating means for estimating a q-axis output voltage from the q-axis current detection value and estimating the back electromotive force component using the q-axis output voltage and a q-axis output voltage command;
Third estimation means for estimating the d-axis interference component using a d-axis current detection value in the magnetic flux axis direction of the electric motor obtained by coordinate conversion of the AC current detection value of the inverter and an angular frequency command of the inverter; Have
The compensation means includes
Using a compensation voltage generated from said d-axis interference component estimated by first the q-axis disturbance voltage estimated by the estimating means and said counter electromotive force component estimated by the second estimation means the third estimation means The output voltage command is corrected.

The invention according to claim 2, Oite the control device of the voltage-type inverter according to claim 1, as an input the d-axis current command value of the flux axis of the motor, coordinate transformation an alternating current detection value of the inverter This is provided with current control means for controlling the d-axis current by feeding back the detected d-axis current value .

The invention according to claim 3 is to control the control device of the voltage-type inverter according to claim 1 or 2 Oite, by the rotational speed V / f constant control of the electric motor.

Invention Oite the control device of the voltage-type inverter as set forth in any one of claims 1 to 3, the first estimating means and / or the second estimation means, the disturbance estimation observer according to claim 4 It is comprised by .

  In the present invention, by using the q-axis voltage command and q-axis current of the inverter, the disturbance voltage including the q-axis voltage error due to the inverter dead time, the back electromotive force component of the motor, and the d-axis interference component is estimated. The inverter output voltage command is corrected using the disturbance voltage as a compensation voltage. At the same time, the d-axis current is fed back to control the d-axis voltage command, thereby controlling the excitation current of the motor in the low speed region.

  Therefore, it is possible to easily compensate for the output voltage distortion of the inverter without requiring complicated processing such as determination of excess or deficiency of the compensation amount and adjustment of the compensation amount as in the prior art, and prevent the occurrence of torque ripple in the motor. At the same time, the harmonics of the AC power supply can be reduced and the control accuracy can be increased. In addition, since the exciting current of the motor is ensured even in open loop control such as V / f constant control, the motor can be driven stably even at low speeds.

  Furthermore, the back electromotive force component of the motor is estimated using the q-axis voltage command and q-axis current of the inverter, and the back electromotive force component included in the disturbance voltage is compensated in the high-speed region, so that the motor can be It can be driven stably.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of this embodiment. In FIG. 1, 1 is a voltage type PWM inverter that outputs an AC voltage having a desired magnitude and frequency, 2 is an induction motor connected to an output terminal of each phase (U, V, W phase) of the inverter 1, frequency setting device for setting the omega ₁ ^* (frequency command for the inverter 1) primary angular frequency command for the induction motor 2, integrated and integrating means for outputting a phase reference signal theta ₁ ^* of the primary angular frequency command omega ₁ ^* 4, Reference _numeral 5 denotes a d-axis voltage command v _1d ^* and a q-axis voltage command v _1q ^* in the rotating magnetic field coordinate system based on the phase reference signal θ ₁ ^* , and each phase voltage command v _u ^* , v _v ^* , v in the stator coordinate system. Coordinate conversion means for converting to _w ^* .

Reference numeral 6 denotes current detection means for detecting the output currents i _u , i _v , i _w of the inverter 1, and 7 denotes the output currents i _u , i _v , i _w of the stator coordinate system based on the phase reference signal θ ₁ ^* . Coordinate conversion means for converting the d-axis current i _1d and the q-axis current i _1q in the rotating magnetic field coordinate system, and V / f conversion means 8 for outputting the q-axis voltage command v _1q ^* from the primary angular frequency command ω ₁ ^* , 9 is a high-speed disturbance estimation observer as a first estimating means for estimating and outputting the disturbance voltage v _dis from the q-axis voltage command v _1q ^* and the q-axis current i _1q , and 10 is the q-axis voltage command v _1q ^* and the q-axis A low-speed disturbance estimation observer as a second estimation means that estimates and outputs the back electromotive force component v _emf from the current i _1q , 11 uses a d-axis current i _1d , a primary angular frequency command ω ₁ ^*, and a leakage inductance L _σ . D-axis interference component v _cmp D-axis interference component computing means 12 as third estimating means for computing, current control means 12 for outputting a d-axis voltage command v _1d ^* with the d-axis current command i _1d ^* and the d-axis current i _1d as inputs, 13 the counter electromotive force component _v subtracting means for subtracting the d-axis interference component _{v cmp} from _emf, subtracting means for outputting a value obtained by subtracting the output of the subtraction means 13 from the disturbance voltage _{v dis} as a compensation voltage _{v c} is 14, 15 is the original q-axis voltage command v _1q ^* and the compensation voltage v _c and the addition to the corrected q-axis voltage command v adding means for outputting _1q ^*.
In the above configuration, the high-speed disturbance estimation observer 9, the low-speed disturbance estimation observer 10, and the d-axis interference component calculation means 11 constitute the voltage distortion component estimation means in the claims, and the subtraction means 13, 14 and the addition means 15 are compensation means. It is composed.

Next, the operation of this embodiment will be described.
The control method in the embodiment shown in FIG. 1 is a known induction motor control method called V / f constant control, and the ratio between the primary angular frequency ω _{1 of the} induction motor 2 and the primary voltage v ₁ is kept constant. This is a method for efficiently controlling the rotation speed of the induction motor 2 over a wide range.

First, the primary angular frequency command ω ₁ ^* set by the frequency setting unit 3 is input to the V / f conversion unit 8, and a primary voltage command (output voltage command) corresponding to the primary angular frequency command ω ₁ ^* is output. The Here, since the d-axis component of the voltage command does not directly affect the torque generated by the induction motor 2, the V / f conversion unit 8 outputs the q-axis voltage command v _1q ^* corresponding to the primary angular frequency command ω ₁ ^{* .} Is output as the primary voltage command. Hereinafter, q-axis voltage command as needed _{v 1q} ^* of the primary voltage command _v ^1q *, the primary voltage of the q-axis voltage _{v 1q v 1q,} shall the q-axis current _{i q} also referred to as primary current _{i q.}

Compensation of the output voltage distortion of the inverter 1 will be described later. The primary voltage command v _1q ^* is input to the coordinate conversion means 5, and the sine wave is converted by coordinate conversion using the phase reference signal θ ₁ ^* from the integration means 4. Output voltage commands v _u ^* , v _v ^* , v _w ^* are generated. According to the PWM signal obtained by comparing these voltage commands v _u ^* , v _v ^* , and v _w ^* with the carrier wave signal in the inverter 1, the semiconductor switching element of the inverter 1 is turned on / off, thereby the inverter 1 Output voltages v _u , v _v , and v _w are controlled and supplied to the induction motor 2.

On the other hand, the output voltage distortion caused by the dead time of the inverter 1 is compensated by the disturbance voltage v _dis estimated by the high-speed disturbance estimation observer 9 in the rotating magnetic field coordinate system.
Here, when the relationship between the primary current i _1q and the primary voltage v _1q of the induction motor 2 is obtained from the voltage equation of the induction motor expressed in the rotating magnetic field coordinate system given by the formula 1, the formula 2 is obtained.

In these formulas,
φ _2d , φ _2q : d-axis motor flux and q-axis motor flux,
v _1d , i _1d : d-axis voltage and d-axis current on the primary side of the induction motor,
v _1q , i _1q : q-axis voltage and q-axis current on the primary side of the induction motor,
ω ₁ : primary angular frequency,
ω _m : rotational angular frequency (electrical angular velocity),
R ₁ : primary resistance value,
R ₂ : secondary resistance value,
L _σ : leakage inductance,
L _m : exciting inductance,
p: a differential operator.

In Equation 2, the second term on the right side is the interference component due to the d-axis, and the fourth term is the back electromotive force component. The third term on the right side is considered to be zero because there is no effect at low speed.
When the sum of the error voltage due to the dead time of the inverter 1 and the d-axis interference component and the back electromotive force component is defined as the disturbance voltage _vdis , Equations 2 to 3 can be obtained.

Here, it is considered that the disturbance voltage v _dis is estimated by a disturbance observer configured in the same manner as in the prior art. That is, based on the relationship between the primary current i _1q and the primary voltage v _1q shown in Formula 3, the output voltage (= (R ₁ + R ₂ + pL _σ ) i _1q ) of the inverter 1 applied to the induction motor 2 is primary. Estimated from current i _1q .
Then, the high-speed disturbance estimation observer 9 takes the difference between the estimated output voltage (= (R ₁ + R ₂ + pL _σ ) i _1q ) and the primary voltage command v _1q ^* as shown in the following equation (4). multiplied by a gain K through T ₁ of the low-pass filter, and outputs as a disturbance voltage estimation value _{^ v dis.} In Equation 4, any value with the symbol “^” is an estimated value.

Here, as the disturbance component due to the dead time, when the primary output frequency is f (= ω ₁ / 2π), an AC ripple component having a frequency six times that appears on the q axis. Accordingly, the time constant T ₁ in Equation 4 is set to the range shown in Equation 5, for example, when the disturbance voltage is estimated in a time sufficiently faster than 6 times the output frequency.

Further, as described above, the disturbance voltage estimated value ^ _vdis includes the back electromotive force component of the induction motor 2 and the interference component due to the d axis in addition to the error voltage due to the dead time. The back electromotive force component is also compensated, and the voltage becomes excessive during open loop control such as V / f control, which causes a problem in stability.
Accordingly, the counter electromotive force component v _emf of the fourth term on the right side in Equation 2 is calculated by the low-speed disturbance estimation observer 10, and the d-axis interference component v _cmp (= ω) of the second term on the right side is calculated by the d-axis interference component calculation unit 11. ₁ L _σ i _1d ) is calculated and inputted to the subtracting means 13 and 14 with the sign shown in the figure, thereby compensating the disturbance voltage estimated value ^ v _dis which is the output of the high-speed disturbance estimation observer 9 and compensating voltage v _c. Is generated.

The slow disturbance estimation observer 10 constitutes a disturbance estimation observer for outputting the estimated back EMF ^ v _emf shown has the same structure as equation 4, the time constant in the formula 6 and T _2.

Here, the back electromotive force v _emf depends on the rotational angular frequency ω ₁ from Equation 2, and the change is very slow with respect to the disturbance component due to the dead time. Therefore, the time constant T ₂ in Equation 6 can be estimated by setting the back electromotive force v _emf to an extent that the disturbance component due to the dead time can be neglected. For example, the time constant T ₂ is set in the range shown in Equation 7.

The estimated back electromotive force ^ v _emf output from the low-speed disturbance estimation observer 10 includes the d-axis interference component v _{cmp of} the second term on the right side of Equation 2, but it is moderate if it is estimated to v _cmp and compensated as a disturbance component. Since stability deteriorates in the high-speed region, this is calculated using the primary angular frequency ω ₁ , the d-axis current i _1d and the leakage inductance L _σ as shown in Formula 8, and is compensated forward.

The d-axis interference component v _cmp calculated as described above is compensated by subtracting it from the estimated counter electromotive force ^ v _emf by the subtracting means 13. The output of the subtraction means 13 compensates for the disturbance voltage estimation value ^ v _dis is input to the next stage of the subtraction means 14, and outputs the result as a compensation voltage v _c.

Since the compensation voltage v _c is applied to the primary voltage command v _1q ^* in addition means 15, the result, estimates only error voltage due to dead time, excluding the counter electromotive force corresponding amount from the disturbance voltage as a voltage distortion component, A system for compensating the primary voltage command v _1q ^* can be configured. Thereby, the output voltage distortion of the inverter 1 can always be minimized.

Next, the current control means 12 will be described.
The current control means 12 sets the output obtained by multiplying the deviation between the d-axis current command i _1d ^* and the d-axis current i _1d by the gain as the d-axis voltage command v _1d ^*, and quickly _sets the d-axis current i _1d to d This is to follow the shaft current command i _1d ^* . In addition, in order to ensure the excitation current in the low speed region of the electric motor 2 independently of the above-described V / f constant control on the q axis, the d axis current command i _1d ^* is set to a constant value (about 30% of the rated current). Current).

As a result of the above, it is possible to prevent the occurrence of torque ripple in the induction motor 2 and to reduce the harmonics of the AC power supply and increase the control accuracy. Furthermore, the feedback control of the d-axis current i _1d makes it possible to drive the electric motor 2 stably even in a low speed region.

  In this embodiment, the case where the induction motor 2 is driven by the inverter 1 is targeted, but the present invention is also applicable to a drive system of another motor such as a synchronous motor. In the present embodiment, the constant V / f control is shown as the control method of the inverter 1, but the present invention can also be applied to other control methods such as vector control.

It is a block diagram which shows embodiment of this invention. It is a block diagram which shows the prior art described in patent document 1. FIG.

Explanation of symbols

1: Voltage type PWM inverter 2: Induction motor 3: Frequency setting means 4: Integration means 5, 7: Coordinate conversion means 6: Current detection means 8: V / f conversion means 9: High-speed disturbance estimation observer (first estimation means) )
10: Low-speed disturbance estimation observer (second estimation means)
11: d-axis interference component calculation means (third estimation means)
12: Current control means 13, 14: Subtraction means 15: Addition means

Claims (4)

A control device for a voltage type inverter that drives an electric motor by outputting an AC voltage of a desired magnitude and frequency by turning on and off a semiconductor switching element, and using the output voltage command and output current of the inverter, the output voltage of the inverter In a voltage type inverter control device comprising:
The voltage distortion component estimation means includes
A q-axis output voltage is estimated from a q-axis current detection value orthogonal to the magnetic flux axis of the motor obtained by converting the AC current detection value of the inverter, and the q-axis output voltage and the q-axis output voltage command are used. a first estimating means for estimating a q-axis disturbance voltage including q-axis output voltage error due to the inverter dead time, the counter electromotive force component of the electric motor, and the d-axis interference component orthogonal to the magnetic flux axis of the motor ,
Second estimating means for estimating a q-axis output voltage from the q-axis current detection value and estimating the back electromotive force component using the q-axis output voltage and a q-axis output voltage command;
Third estimation means for estimating the d-axis interference component using a d-axis current detection value in the magnetic flux axis direction of the electric motor obtained by coordinate conversion of the AC current detection value of the inverter and an angular frequency command of the inverter; Have
The compensation means includes
Using a compensation voltage generated from said d-axis interference component estimated by first the q-axis disturbance voltage estimated by the estimating means and said counter electromotive force component estimated by the second estimation means the third estimation means A control apparatus for a voltage type inverter , wherein the output voltage command is corrected. In the voltage type inverter control device according to claim 1,
Current control means for controlling the d-axis current by feeding back the d-axis current detection value obtained by converting the alternating current detection value of the inverter with the d-axis current command value in the magnetic flux axis direction of the motor as an input. A control device for a voltage type inverter characterized by the above. In the control apparatus of the voltage type inverter according to claim 1 or 2,
A voltage type inverter control device, wherein the rotation speed of the electric motor is controlled by V / f constant control . In the control apparatus of the voltage type inverter as described in any one of Claims 1-3,
A control apparatus for a voltage type inverter, wherein the first estimation means and / or the second estimation means is constituted by a disturbance estimation observer .

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