JP2009213212A - Variable-speed driving device for synchronous motors - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem that arises when an alternating current signal is added to a q-axis current command to forcedly produce a high-frequency torque ripple in a variable-speed driving device for synchronous motors: when a voltage component becomes higher than the outputtable maximum voltage of an inverter, voltage saturation occurs and thus it is impossible to accurately generate a current command. <P>SOLUTION: An alternating current signal generator is caused to generate a d-axis high-frequency current command delayed by a phase of 90° from a q-axis high-frequency current command. This d-axis high-frequency current command is added to a d-axis current command and the result of this addition is input to a current control unit. When a synchronous motor is reversely rotated, this d-axis high-frequency current command is advanced by a phase of 90° from the q-axis high-frequency current command. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a variable speed drive device for a synchronous motor, and more particularly to a control device for simulating torque ripple.

  For driving a synchronous motor known as a permanent magnet type synchronous motor (PM motor) or a field winding type synchronous motor, vector control is generally performed based on a signal detected by a position sensor attached to the motor. Such a control apparatus is used for speed and position control of a position servo or the like, but there are cases where it is desired to generate vibration torque during rotation at a constant speed. For example, this corresponds to the case where it is desired to simulate the torque ripple of the engine of the power measuring device.

FIG. 4 shows the prior art of a variable speed drive device that can simulate torque ripple by generating vibration torque. Usually, the magnetic pole axis is defined as d-axis and its orthogonal axis is defined as q-axis. A current command (high-frequency current command) corresponding to a high-frequency torque component for generating torque is generated from the AC signal generator 3 and superimposed on the q-axis current command from the current command converter 2. The difference between the q-axis current command and the detected current i _q after superimposition and the difference between the d-axis current “0” command and the detected current i _d are respectively input to the current controller (ACR control) 4 and output voltage command vd. ^{* And} vq * are output. The output voltage commands vd ^* and vq * are respectively input to the two-phase / three-phase coordinate converter 5 and converted into a three-phase AC voltage command, and the inverter 7 is switched via the PWM circuit 6 based on the AC voltage command. Control the element.

The high-frequency current and the generated voltage in the variable speed driving device when the PM motor is taken as an example are as follows.
Assuming that the dq coordinates are orthogonal two-axis coordinates rotating at a constant fundamental wave angular frequency ω, the voltage-current equation of the PM motor is expressed by equation (1).

Where v _d and v _q are dq axis voltages, i _d and i _q are dq axis currents, R is resistance, L _d is d axis inductance, L _q is q axis inductance, p is a differential operator, and ω is a fundamental wave. Angular frequency, φ _d is permanent magnet magnetic flux (φ _q = 0)
Here, when the PM motor is operated at a constant fundamental wave angular frequency ω and the steady current component i _d0 is i _q0 , the high frequency currents Δi _d and Δi _q are input to generate vibration torque, and the dq axis The currents i _d and i _q are as shown in equation (2).

If this equation (2) is substituted into the voltage-current equation of equation (1), it can be separated into a voltage component due to steady current and a voltage component due to high-frequency current as in equation (3).

Here, assuming that the fundamental wave angular frequency ω is high and the frequency component ω _{v of the} high-frequency current is also sufficiently high, the voltage drop component due to R in the third term on the right side of equation (3) is generated by other inductances. Ignore it because it is much smaller than the voltage to be applied. The differential operator p in the first term is omitted because i _d0 and i _q0 are steady current components. Therefore, when the voltage component generated by the steady current and the voltage component generated by the high-frequency current are separated by the above approximation, the respective components are expressed by the equations (5) and (6). Become.

Next, generation of the high-frequency current command in FIG. 4 will be described.
A sinusoidal high frequency current command is applied from the AC signal generator 3 only to the q-axis component while the d-axis current is fixed at zero. In this case, this corresponds to applying a current as shown in equation (7). The high-frequency voltage component output from the current controller 4 to generate a high-frequency current corresponding to this high-frequency current command is obtained by substituting Equation (7) into Equation (6) as shown in Equation (8).

Where Δi _qv is the amplitude current of the high frequency current and ω _v is the angular frequency of the high frequency current.

The high-frequency current component of equation (7) is only the q-axis component, but both high-frequency voltage dq axial components are generated. From equation (8), it can be seen that an amplitude voltage proportional to the fundamental angular frequency ω component is generated on the d-axis, and an amplitude voltage component proportional to the high-frequency angular frequency ω _v is generated on the q-axis voltage. Since these are a sin function and a cos function with the same angular frequency ω _v , an elliptical voltage locus is drawn on the dq axis coordinates.
FIG. 5 shows steady current components (i _d0 , i _q0 ) and high-frequency current components (Δi _d , Δi _q ) on the dq axis coordinates. Here, the mathematical expression in FIG. 5 is expressed by using d and q unit vectors of the expression (9). Similarly, FIG. 6 shows the locus of the voltage component.

Patent Document 1 is known as a device that generates vibration torque.
JP-A-8-137555

The conventional high-frequency component is -ωL _q · Δi _qv · sin (ω _v t) and the q axis component is ω _v L _q · Δi _qv · cos (ω _v t) as shown in equation (8). The trajectory they draw becomes elliptical. If the voltage component in FIG. 6 becomes larger than the maximum output possible voltage of the inverter (broken line in the figure), voltage saturation occurs, so that the current command in FIG. 5 cannot be generated accurately. Yes.

  Accordingly, an object of the present invention is to provide a variable speed drive device for a synchronous motor capable of expanding the amplitude and frequency of a high frequency current command while preventing voltage saturation.

Claim 1 of the present invention provides a variable speed drive device for a synchronous motor that can arbitrarily generate a torque ripple by adding a q-axis high-frequency current command to a q-axis current command.
The d-axis high-frequency current command having a phase delayed by 90 ° with respect to the q-axis high-frequency current command is added to the d-axis current command.

  The second aspect of the present invention is characterized in that the d-axis high-frequency current command has a phase advance of 90 ° with respect to the q-axis high-frequency current command when the synchronous motor is reversely rotated.

According to a third aspect of the present invention, there is provided a variable speed drive device for a synchronous motor capable of arbitrarily generating a torque ripple by adding a q-axis high-frequency current command to a q-axis current command.
The current command obtained by differentiating the q-axis high-frequency current command is added to the d-axis current command.

  A fourth aspect of the present invention is characterized in that the current command obtained by differentiating the q-axis high-frequency current command switches between positive and negative depending on the polarity of the fundamental wave frequency between normal rotation and reverse rotation.

  As described above, according to the present invention, the q-axis high-frequency current command necessary for generating torque and the AC current command component delayed by 90 ° with respect to the high-frequency current command are added to the d-axis current command. It is what you do. As a result, the armature reaction component due to the d-axis component and the transformer electromotive force component due to the change in the d-axis current act so as to reduce the high-frequency voltage generated by the q-axis current, resulting in an elliptical shape. The amplitude component of the high frequency voltage component can be reduced, and voltage saturation can be prevented. Conversely, the torque ripple amplitude limit and frequency limit due to the high-frequency current command can be further expanded.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which the same or corresponding parts as in FIG.
_{Reference numeral} 1 denotes a speed control unit which receives a difference between the speed command ω _r ^* and the speed detection signal ω _r from the speed detection unit 13 and calculates a torque command T _rq ^* for controlling the speed. _{Reference numeral} 2 denotes a current command conversion unit, and the obtained torque command T _rq ^* is input to the current command conversion unit 2 and converted into a q-axis current component. _{Reference numeral} 30 denotes an AC signal generator from which sinusoidal high-frequency current commands i _qv * and i _dv * are output. The high-frequency current command i _qv * is added to the output of the current command conversion unit 2 to become a current command i _q *, and the difference from the detected current i _q is obtained in the subtraction unit, and this difference is input to the current control unit 4Q to obtain the voltage Command is calculated.

On the other hand, the high-frequency current command i _dv * from the AC signal generator 30 is added to the d-axis command fixed to zero to obtain a d-axis current command i _d *, and a difference from the detected current i _d is obtained. The voltage command is calculated by inputting the difference to the current control unit 4D. The coordinate converter 5 receives the voltage command from the current controller 4 and the position signal θ from the position detector 11 and generates a three-phase AC voltage command by rotational coordinate conversion and two-phase / 3-phase coordinate conversion. The PWM circuit 6 receives the generated voltage command and performs equivalent conversion to a PWM signal. The switching element of the inverter 7 is on / off controlled by the converted PWM signal, and the PM motor 8 is controlled by the power amplified voltage. The rotational position of the motor 8 is detected by the position detector 11 via the encoder 10. The detected position signal θ is output to the coordinate converter 12 and the speed detector 13. Coordinate converter 12 outputs a detection current i _q, i _d by the coordinate conversion by the reverse rotation of the current detector 9 detects current detected by the 3-phase / 2-phase coordinate transformation and coordinate converter 5.

  In the present invention shown in FIG. 1, the maximum value of the voltage component obtained by synthesizing the steady component and the high frequency component shown in FIG. 6 is reduced to increase the margin until voltage saturation occurs, and the torque ripple caused by the high frequency current command that can be generated. It is found that the limit value of the amplitude and frequency can be expanded, and the current command of the AC component is added to the d-axis current. Therefore, a case where a high-frequency component is added to the d-axis current is examined. Corresponding to equation (7), consider a case where high-frequency current is generated in both the d-axis and the q-axis as in equation (10).

Where Δi _dv is the amplitude component of the high-frequency current of the d-axis current, Δi _qv is the amplitude component of the high-frequency current of the q-axis current,
Here, as shown in FIG. 2, the d-axis is set so that the generated high-frequency current rotates clockwise (CW). The high frequency voltage generated by this current component is obtained by substituting Equation (10) into Equation (6), and is obtained as Equation (11).

Since Δv _d and Δv _q are functions of sin (ω _v t) and cos (ω _v t) in the same manner as in equation (8), the equation (11) is an elliptical shape as in the prior art of FIG. The voltage locus is drawn, but the amplitude component is different.
Compared with the voltage component of equation (8), as shown in FIG. 3, the voltage component generated by the d-axis high-frequency current and the voltage component generated by the q-axis current are always located in the diagonal direction of the high-frequency voltage center. Therefore, when these two types of voltage components are combined, the maximum amplitude of the voltage components becomes smaller than that in FIG. This voltage reduction amount is proportional to the fundamental frequency, and the phenomenon that the voltage margin decreases as the frequency increases can be improved.
Here, the d-axis current in the equation (11) is delayed by 90 ° in the case of normal rotation with respect to the q-axis current, but it may be advanced by 90 ° in order to maintain symmetry in the case of reverse rotation.

Although the two-phase oscillator is used in the expression (11) of the above embodiment, a single-phase alternating current of the expression (12) is generated as in the conventional example, and the d-axis current is the expression (12) as in the expression (13). May be obtained by differentiating. However, in order to control the phase lead and lag by the fundamental frequency, keep switching the positive and negative d-axis high frequency current component .DELTA.i _d by in response to positive and negative polarities of the fundamental wave angular frequency omega sign (omega) function.

In the above description, the PM motor has been described as an example, but the same effect can be obtained in the case of a field winding type synchronous motor.

  According to the present invention described above, in a variable speed drive device for a synchronous motor that forcibly generates a high-frequency torque ripple, a q-axis high-frequency current command necessary for generating torque and the high-frequency current command The AC current command component delayed by 90 ° phase is added to the d-axis current command. The armature reaction component due to the added d-axis component and the transformer electromotive force component due to the change in d-axis current act to reduce the high-frequency voltage generated by the q-axis current. Thereby, the amplitude component of the high frequency voltage component which is elliptical can be reduced, and voltage saturation can be prevented. Conversely, the torque ripple amplitude limit and frequency limit due to the high-frequency current command can be further expanded.

The block diagram of the variable speed drive device which shows embodiment of this invention. Explanatory drawing of q-axis and d-axis separation of high-frequency current. The locus | trajectory explanatory drawing of the voltage component and its synthetic voltage by a high frequency current. The block diagram of the variable speed drive device at the time of the conventional vibration torque generation | occurrence | production. Explanatory drawing of a q-axis high frequency current component. Explanatory drawing of the locus | trajectory of the voltage component by a q-axis high frequency component.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Speed control part 2 ... Current command conversion part 3, 30 ... AC signal generator 4 ... Current controller 5 ... 2-phase / 3-phase coordinate converter 6 ... PWM circuit 7 ... Inverter 8 ... PM motor 9 ... Current detector DESCRIPTION OF SYMBOLS 10 ... Encoder 11 ... Position detector 12 ... 3 phase / 2 phase coordinate converter 13 ... Speed detector

Claims (4)

In a variable speed drive device for a synchronous motor that can arbitrarily generate a torque ripple by adding a q-axis high-frequency current command to a q-axis current command,
A variable speed drive device for a synchronous motor, wherein a d-axis high-frequency current command delayed by 90 ° with respect to the q-axis high-frequency current command is added to the d-axis current command. 2. The variable speed drive device for a synchronous motor according to claim 1, wherein the d-axis high-frequency current command is advanced by 90 ° with respect to the q-axis high-frequency current command when the synchronous motor is reversely rotated. In a variable speed drive device for a synchronous motor that can arbitrarily generate a torque ripple by adding a q-axis high-frequency current command to a q-axis current command,
A variable speed drive device for a synchronous motor, wherein a current command obtained by differentiating the q-axis high-frequency current command is added to a d-axis current command. 4. The synchronous motor according to claim 3, wherein the current command obtained by differentiating the q-axis high-frequency current command switches between positive and negative of the d-axis high-frequency current component in accordance with forward and reverse polarities of the fundamental frequency. Variable speed drive.

Images