JP2003264999A - Vector control device for ac motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vector control device capable of achieving high-efficiency drive of an AC motor. <P>SOLUTION: The vector control device operates a voltage vector phase so that a motor-torque component current feed-back value follows a torque- component command value. The device is also characterized in that a voltage- vector amplitude command is made variable corresponding to a flux-component current feed-back value. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control device for an AC motor such as a permanent magnet motor, a reluctance motor or an induction motor.

[0002]

2. Description of the Related Art Conventionally, in order to control the output torque of an AC motor of this type with high accuracy, current feedback control is generally performed on the Cartesian coordinates dq axes that rotate in synchronization with the rotating magnetic flux of the motor. Is.

However, when the dq-axis current feedback control is performed, in a high-speed rotation operation state in which the maximum voltage that can be output by the inverter is exceeded, depending on the configuration of the limit process of the proportional-integral control that constitutes the current feedback control. May be unstable in control.

On the other hand, the inventor previously proposed a method of fixing the voltage vector amplitude and controlling the motor torque by operating only the voltage vector phase (Japanese Patent Laid-Open No. 09-
No. 084399).

[0005]

However, in the previously proposed voltage vector amplitude fixed and voltage vector phase manipulation control method, the voltage vector amplitude is determined by using the motor equivalent circuit model and the current command value. If the set value of the motor equivalent circuit constant is different from that of the actual machine, the current operating point will be different from the assumed operating point.

The above-mentioned case where the current operating point is different from the assumed operating point specifically means that the magnetic flux component current is different from the magnetic flux component current command. In this case, unnecessary weakening magnetic flux current or strengthening Magnetic flux current flows. Therefore, it is assumed that the efficiency will decrease due to the increase of motor copper loss.

An object of the present invention is to provide a vector control device that achieves highly efficient driving of an AC motor.

[0008]

In order to achieve the above object, the present invention relates to a vector of an AC motor which operates a voltage vector phase so that a motor torque component current feedback value follows a torque component current command value. In the control device, the voltage vector amplitude command is variable according to the magnetic flux component current feedback value.

According to the present invention, the voltage vector amplitude is fixed,
In the voltage vector phase operation control method, by changing the voltage vector amplitude according to the deviation between the magnetic flux component current feedback value and the command value, the magnetic flux component current matches the optimum magnetic flux component current setting, and motor efficiency is improved. Is achieved.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment: Corresponding to Claim 1) FIG.
As shown in FIG. 4, the vector control device for an AC motor of this embodiment is applied to an inverter that drives an AC motor as a main circuit, and the dq axis voltage model calculation unit 11
A polar coordinate converter 12, an amplitude corrector 13, a phase corrector 14, a voltage amplitude calculator 15, and a voltage phase calculator 16.
And a PWM waveform calculation unit 17.

The d-axis current command IdRef and the q-axis current command IqRef are given to the dq-axis voltage model calculation unit 11, and the dq-axis voltage model calculation unit 11 calculates the d-axis voltage command Vd and the q-axis voltage command by the following calculation. Vq is obtained and output.

Vd = R · IdRef−ω · Lq · IqRef Vq = R · IqRef + ω · Ld · IdRef + ω · Φ
PM (R: resistance, Ld, Lq: dq axis inductance, ω:
dq-axis rotation frequency, ΦPM: Permanent magnet magnetic flux) In the polar coordinate conversion unit 12, the dq-axis voltage commands Vd and Vq output from the dq-axis voltage model calculation unit 11 are input, and the voltage vector amplitude V1 is obtained by the following calculation. , And obtains and outputs the voltage vector phase δ.

[0014]

[Equation 1]

The amplitude correction unit 13 receives the d-axis current command IdRef and the d-axis current feedback value Id obtained from the main circuit side as input, and calculates and outputs the voltage vector amplitude correction value ΔV1 by the following calculation.

ΔV1 = G (s)  (IdRef-Id) (s is a Laplace operator, G (s) is a control gain) In the phase correction value calculator 14, the q-axis current command IqR
ef and the q-axis current feedback value Iq obtained from the main circuit side are input, and the voltage vector phase correction value Δδ is obtained and output by the following calculation.

Δδ = H (s) · (IqRef-Iq) (S is the Laplace operator, H (s) is the control gain) As H (s), proportional / integral control can be considered.

In the voltage amplitude calculator 15, the voltage vector amplitude V1 output from the polar coordinate converter 12 and the voltage vector amplitude correction value ΔV output from the amplitude corrector 13 are shown.
With 1 as an input, a new voltage vector amplitude V1 'is obtained and output by the following calculation.

V1 '= V1-.DELTA.V1 In the voltage phase calculator 16, the voltage vector phase .delta. Output from the polar coordinate converter 12 and the voltage vector phase correction value .DELTA..delta. A new voltage vector phase δ ′ is calculated and output.

Δ ′ = δ + Δδ In the PWM waveform calculation unit 17, the voltage amplitude calculation unit 15
The voltage vector amplitude V1 ′ output from the voltage phase calculation unit 16, the voltage vector phase δ ′ output from the voltage phase calculation unit 16, and the motor rotor phase θ obtained by a sensor or the like attached to an AC motor (not shown) are input as follows. Three-phase voltage commands VuRef, VvRef, VwRef are obtained by calculation.

[0021]

[Equation 2]

Inverter output PWM waveforms Vu, Vv, V
w is obtained by a generally used triangular wave comparison method, and is given to the switching element of each phase of the inverter (not shown). In this case, the triangular wave TRI has an amplitude Vdc / 2.
(Vdc is an inverter input DC voltage) and the frequency is, for example, 5 kHz, which is higher than the inverter output frequency.

(1) When VuRef> TRI, Vu = Vdc / 2 VuRef <TRI, Vu = −Vdc / 2 (2) When VvRef> TRI, Vv = Vdc / 2 VvRef <TRI, Vv = -Vdc / 2 (3) When VwRef> TRI, Vw = Vdc / 2 When VwRef <TRI, Vw = -Vdc / 2 As described above, in this embodiment, the voltage vector amplitude is fixed and the voltage vector is fixed. Under the phase operation control,
The amplitude correction unit 13 obtains the voltage vector amplitude correction value ΔV1 using the d-axis current command IdRef and the d-axis current feedback value Id obtained from the main circuit side, and the voltage vector amplitude correction value ΔV1 is output from the polar coordinate conversion unit 12. By subtracting from the amplitude V1, the voltage vector amplitude corresponding to the deviation between the magnetic flux component current feedback value and the command value is obtained.

Therefore, since the voltage vector amplitude is variable according to the deviation between the magnetic flux component current feedback value and the command value, the magnetic flux component current is made to match the optimum magnetic flux component current setting, and unnecessary weakening magnetic flux current or strengthening is performed. It is possible to perform voltage vector phase control without causing a problem such as a decrease in efficiency due to an increase in motor copper loss due to magnetic flux current.

(Second Embodiment: Corresponding to Claim 2) FIG.
As shown in FIG. 7, the vector control device for an AC motor according to the second embodiment can switch between the PWM voltage waveform output operation mode and the 1-pulse voltage waveform output operation mode according to the first embodiment, The problem is suppressed, and the dq axis voltage model calculation unit 11, the polar coordinate conversion unit 12, the amplitude correction unit 13, the phase correction unit 14, and the voltage amplitude calculation unit 15 that are the constituent elements of the first embodiment. In addition to the voltage phase calculation unit 16 and the PWM waveform calculation unit 17, the maximum value determination unit 21, the 1-pulse waveform calculation unit 22, and the PWM
The 1-pulse switching unit 23 is additionally provided.

The dq-axis voltage model calculation unit 11, the polar coordinate conversion unit 12, the phase correction unit 14, and the voltage amplitude calculation unit 15
The operations of the voltage phase calculation unit 16 and the PWM waveform calculation unit 17 are the same as those in the first embodiment, and the voltage vector amplitude is fixed and the voltage vector phase operation control is performed as the PWM voltage waveform output operation mode. Since the voltage vector amplitude is variable according to the deviation between the magnetic flux component current feedback value and the command value, the magnetic flux component current can be matched with the optimum magnetic flux component current setting.

The one pulse voltage waveform output operation mode operates as follows. That is, the maximum value determination unit 21
In, the voltage vector amplitude V1 ′ output from the voltage amplitude calculator 15 is input, and the voltage vector maximum flag PWMmode is output by the following conditional branch.

First, the maximum voltage vector amplitude V1Max that can be output by the inverter is obtained by the following calculation.

[0029]

[Equation 3] (1) When V1 ′> V1Max, PWMmode = 1 (2) When V1 ′ <V1Max, PWMmode = 0 In the amplitude correction unit 13, the d-axis current command IdRef
, D-axis current feedback value Id, and maximum value determination unit 2
Maximum voltage vector flag PWMmod output from 1
Using e as an input, the voltage vector amplitude correction value ΔV1 is obtained and output by the following calculation.

(1) When PWMmode = 0, ΔV1 = G (s)  (IdRef-Id) (s is Laplace operator, G (s) is control gain) (2) When PWMmode = 1, (a ) When IdRef> Id, ΔV1 = G (s) · (I
dRef−Id) (b) When IdRef <Id, ΔV1 holds the previous value. 1 In the pulse waveform calculation unit 22, the voltage phase calculation unit 1
Three-phase one-pulse waveforms Vu1p, Vv1p, and Vw1p are obtained and output by the following calculation using the voltage vector phase δ ′ output from 6 and the motor rotor phase θ as input.

(1) When 0 ° <(θ + δ ′ + 90 °) <180 °, Vu1P = Vdc / 2 When 180 ° <(θ + δ ′ + 90 °) <360 °, Vu1P = −Vdc / 2 (2) 0 ° <(θ + δ ′ + 90 ° -120 °) <180
When °, Vv1P = Vdc / 2 180 ° <(θ + δ ′ + 90 ° −120 °) <360 °
At that time, Vv1P = −Vdc / 2 (3) 0 ° <(θ + δ ′ + 90 ° −240 °) <180
When °, Vw1P = Vdc / 2 180 ° <(θ + δ ′ + 90 ° −240 °) <360 °
At this time, Vw1P = −Vdc / 2 In the PWM1 pulse switching unit 23, the three-phase PWM waveforms VuPWM, Vv output from the PWM waveform calculation unit 17
PWM, VwPWM, and three-phase one-pulse waveform Vu1p, Vv1p, Vw1 output from the one-pulse waveform calculator 22
p and the voltage vector maximum flag PWMmode flag output from the maximum value determination unit 21 are input, and three-phase pulse waveforms Vu, Vv, and Vw are obtained and output by the following conditional branch.

(1) When PWMmode = 1, Vu = Vu1p Vv = Vv1p Vw = Vw1p (2) When PWMmode = 0, Vu = VuPWM Vv = VvPWM Vw = VwPWM With the vector controller of the AC motor having the above configuration, It is possible to operate by switching between the PWM voltage waveform output operation mode and the 1-pulse voltage waveform output operation mode. In this case, in the PWM 1-pulse switching unit 23, the three-phase pulse waveforms Vu, Vv, Vw according to the conditional branching described above. Since it is possible to output, it is possible to suppress a transient phenomenon such as current discontinuity associated with switching between the two modes and perform smooth switching.

(Third Embodiment: Corresponding to Claim 3) FIG.
As shown in FIG. 3, the AC motor vector control device according to the third embodiment is a component of the AC motor vector control device according to the third embodiment as shown in FIG. a dq-axis voltage model calculation unit 11,
Polar coordinate conversion unit 12, amplitude correction unit 13, and phase correction unit 1
4, a voltage amplitude calculator 15, a voltage phase calculator 16,
In addition to the PWM waveform calculation unit 17, the control mode determination unit 31
And a d-axis current control unit 32 and a q-axis current control unit 33.

Here, the dq axis voltage model calculation unit 11 and
Voltage amplitude calculator 15, voltage phase calculator 16, PWM
The operation of the waveform calculator 17 is the same as that of the first embodiment.

In the control mode determination unit 21, the voltage vector amplitude V1 'output from the voltage amplitude calculation unit 15 is input, and the following conditional branch is performed to switch between the dq axis current feedback control mode and the voltage phase control mode. A control mode flag VECmode for performing the above is output.

The switching voltage vector amplitude set value V1CHG is obtained by the following calculation.

[0037]

[Equation 4] (RATE is a value larger than 0 and smaller than 1) From the above equation, the maximum voltage V1Max that can be output by the inverter is obtained.
On the other hand, the dq-axis current feedback control and the voltage phase control mode can be switched with a small value of a fixed ratio. In the voltage phase control mode described in the first embodiment, stable operation may not be obtained in an operating region where the voltage amplitude is small, such as near zero speed.

On the other hand, in the dq-axis current feedback control, control instability may occur in an operating region where the voltage amplitude is close to the inverter output maximum voltage.

Therefore, in order to make up for the drawbacks of both of them and to switch the quantity control mode in an operating region where they can operate stably, it is desirable to select RATE from around 0.5 to 0.9. Of course, other values can achieve the purpose.

(1) When V1 ′> V1CHG, VECmode = 1 (2) When V1 ′ <V1CHG, VECmode = 0 The operations of the voltage amplitude correction unit 13 and the voltage phase correction unit 14 are basically the first operation. The same as the embodiment, but the control mode flag VECm output from the control mode determination unit 21.
When VECmode = 1 with new input of ode, the same operation as in the first embodiment is performed, and VECmo
When de = 0, the output is held and the operation is not performed.

In the d-axis current controller 32, the d-axis current command IdRef, the d-axis current feedback value Id,
The d-axis voltage command Vd output from the dq-axis voltage model calculation unit 11 is input, and a new d-axis voltage command Vd is obtained and output.

[0042] Vd = Vd + K (s) (IdRef-Id) (S is the Laplace operator, K (s) is the control gain) Proportional integral control is conceivable as K (s).

In the q-axis current controller 33, the q-axis current command IqRef, the q-axis current feedback value Iq,
The q-axis voltage command Vq output from the dq-axis voltage model calculation unit 11 is input to obtain and output a new q-axis voltage command Vq.

[0044] Vq = Vq + L (s) (IqRef-Iq) (S is the Laplace operator, L (s) is the control gain) Proportional-integral control can be considered as L (s).

With the vector control device for the AC motor having the above-described structure, the voltage phase control mode has a drawback that stable operation cannot be obtained in an operating region where the voltage amplitude is small such as near zero speed, and the dq-axis current feedback control has. Since both of the drawbacks of control instability in the operating region where the voltage amplitude is close to the maximum voltage that can be output by the inverter can be compensated for each other, stable control can be performed in the entire speed region.

[0046]

As described above, according to the present invention, in the voltage vector amplitude fixed and voltage vector phase operation control system, the voltage vector amplitude is made variable according to the deviation between the magnetic flux component current feedback value and the command value. Thus, it is possible to provide a vector control device for an AC motor that can match the magnetic flux component current with the optimum magnetic flux component current setting and achieve high efficiency of the motor.

[Brief description of drawings]

FIG. 1 is a block diagram of a vector control device for an AC motor according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a vector control device for an AC motor according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a vector control device for an AC motor according to a third embodiment of the present invention.

[Explanation of symbols]

11 ... dq-axis voltage model calculator 12 ... Polar coordinate converter 13 ... Amplitude correction unit 14 ... Phase correction unit 15 ... Voltage amplitude calculator 16 ... Voltage phase calculator 17 ... PWM waveform calculator 21 ... Maximum value determination unit 22 ... 1 pulse waveform calculator 23 ... PWM 1 pulse switching unit 31 ... Control mode determination unit 32 ... d-axis current controller 33 ... q-axis current controller

Claims (3)

[Claims] 1. A vector control device for an AC motor, which operates a voltage vector phase so that a motor torque component current feedback value follows a torque component current command value, wherein the voltage vector amplitude command corresponds to a magnetic flux component current feedback value. A vector control device for an AC motor, comprising: 2. When the voltage vector amplitude command is larger than the maximum voltage that can be output by the inverter, the output voltage is synchronized with the inverter frequency to output a one-pulse waveform that is turned on and off once per cycle, and the voltage vector amplitude command is output. 2. The vector of the AC motor according to claim 1, further comprising switching means for switching the voltage waveform so as to output a pulse width modulation waveform corresponding to the voltage command when is smaller than the maximum voltage that can be output by the inverter. Control device. 3. The current feedback on the orthogonal dq coordinate axes rotating in synchronization with the rotor of the AC motor on condition that the voltage vector amplitude command has become a certain ratio or less with respect to the maximum inverter output voltage. 2. The vector control device for an AC motor according to claim 1, further comprising switching means for switching control modes so as to perform control.