JP2000287494A - Control device for synchronous motor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the upper limit of torque that can be output at the time of low speed of a synchronous motor and shorten the acceleration / deceleration time. A current detector (2) for controlling the magnitude of an armature current of a synchronous motor (70) to match a current command value and controlling the frequency of the armature current to match the frequency command value.
1, a first control means including a coordinate converter 22, current adjusters 23 and 24, a frequency integrator 13, and the like; the magnitude of the terminal voltage is made substantially proportional to the frequency command value; F / V that controls to match the command value
The power converter 60 is controlled by the output of the second control means when the frequency is high, and the first control means is controlled by the output of the second control means when the frequency is high. Power converter 6 by the output of the control means
Control switch 2 for switching the control operation to control 0
6, a changeover switch 27 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a synchronous motor that operates without using a magnetic pole position detector (such as a Hall element, an encoder, and a resolver).

[0002]

2. Description of the Related Art As a method of operating a synchronous motor without using a magnetic pole position detector, there is a V / f control for controlling a motor terminal voltage almost in proportion to a frequency. FIG. 6 shows a block diagram of a control device for operating a permanent magnet synchronous motor by V / f control as a conventional technique.

In FIG. 6, the rate of change of the first frequency command f ₀ ^* is limited by a ramp function, so that the second frequency command f ^*
Is calculated. The f / V converter 11 calculates voltage commands v _d ^* , v _q ^* on the dq axes from f ^* . Polar coordinate converter 1
2 calculates the magnitude V ^{* of the} terminal voltage and the angle φ with respect to the d axis from v _d ^* and v _q ^* . Here, the dq axis is an arbitrary rotating coordinate axis that rotates according to the frequency command f ^* , and the d axis is defined as an arbitrary direction, and a direction advanced by 90 ° from the d axis is defined as a q axis.
The relationship between _vd ^* , _vq ^* and V ^* , φ is as shown in FIG. The polar coordinate converter 12 calculates V ^* and φ by Expressions 1 and 2
Is calculated by

[0004]

[Number 1] _{^{V * = √ (v d *}} 2 + v q * 2)

[0005]

## EQU2 ## φ = tan ^-1 (v _q ^* / v _d ^* )

The second frequency command f ^* is transmitted to the frequency integrator 13
Is added by an adder 14, and a voltage command calculator 15 is calculated from the addition result and V ^*.
By the three-phase voltage command _{^{v u *, v v *,}} v to calculate the _w ^*. These three-phase voltage commands are transmitted to the power converter 6 by the PWM circuit 16.
The terminal voltage of the permanent magnet synchronous motor (PM motor) 70 is controlled by controlling the power converter 60 by converting the signal into a gate signal of 0. As a result, the rotation frequency of the electric motor 70 can be made to match the frequency command f ^* . In addition, 5
0 is a power supply.

[0007]

The stability of the above-described V / f control is reduced due to the effect of the voltage drop due to the armature resistance and the output voltage error caused by the power converter 60 during the low-speed operation of the motor 70. As a result, the upper limit of the torque that can be output during low-speed operation decreases,
Problems such as prolonged acceleration / deceleration time occur. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a control device for a synchronous motor capable of improving the stability in such a low-speed operation range, increasing the torque upper limit, and shortening the acceleration / deceleration time.

[0008]

In order to solve the above-mentioned problems, according to the present invention, when the motor is operated at a low speed, the magnitude of the current is kept constant and the frequency of the current is made to coincide with the frequency command value. A synchronous pull-in operation is performed by generating a magnetic field, and when a predetermined frequency is reached, the conventional V / f
It was decided to switch to control. As a result, the stability at the time of low-speed operation is improved, and the upper limit of the output torque can be increased, so that the acceleration / deceleration time can be reduced. In addition, means for controlling the phase of the terminal voltage, means for limiting the rate of change of the magnitude, and the like are provided in order to alleviate the shock when the control is switched between the low-speed operation mode and the high-speed operation mode.

That is, according to the first aspect of the present invention, in a control device for controlling a synchronous motor having no magnetic pole position detector by a power converter, an armature current and a terminal voltage of the synchronous motor are taken as vectors, and First control means for controlling the magnitude of the current to match the current command value and controlling the frequency of the armature current to match the frequency command value; and making the magnitude of the terminal voltage substantially proportional to the frequency command value. And a second control means for controlling the frequency of the terminal voltage to match the frequency command value, and controlling the power converter by the output of the second control means when the frequency is high, and controlling the power converter when the frequency is low. Switching means for switching the control operation to control the power converter based on the output of the first control means.

According to a second aspect of the present invention, in the control device for a synchronous motor according to the first aspect, when the control operation by the first control means is switched to the control operation by the second control means, the terminal voltage of the synchronous motor is changed. And control means for controlling the phase to be equal before and after switching, and limiting means for limiting the rate of change of the magnitude of the terminal voltage.

[0011] The invention according to claim 3 is the invention according to claim 1 or 2.
In the control device for a synchronous motor described above, the first control means has an integration element for calculating a terminal voltage command value by integrating at least a deviation between the current command value and the current detection value. A first function of presetting the output of the integration element or a current command value so that the phase and magnitude of the terminal voltage become equal before and after the switching when the control operation is switched to the control operation by the first control means. A second function of presetting an initial value of and switching to the control operation by the first control means at a predetermined change rate, or
It is characterized by having both the first and second functions.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIG. 1 is a control block diagram of the first embodiment of the present invention, and the same components as those in FIG. 6 are denoted by the same reference numerals. This embodiment corresponds to the first embodiment of the present invention. The embodiment of FIG. 1 is obtained by adding a function surrounded by a dashed line to the configuration of FIG.
During high-speed operation, the motor is driven by the conventional V / f control, and during low-speed operation, the magnitude of the current of the motor is controlled to be constant to perform the synchronous pull-in operation.

The added functions are a current detector 21 for obtaining a two-phase current of the synchronous motor 70, a coordinate converter 22 for converting the detected current values i _u , i _w into dq components,
The d-axis current adjusters 23 and q that operate to adjust the detected d and q-axis current values i _u and i _w to the respective command values _id ^* and _iq ^*.
Frequency command f ^{* of} shaft current controller 24 and synchronous motor 70
A changeover switch 2 for switching between the output of the f / V converter 11 and the output of each of the regulators 23 and 24 according to (operating speed)
5 and a control switch 26 for driving the switch 25
It is a part consisting of

In the above configuration, the current detector 21, the coordinate converter 22, the d-axis current controller 23, and the q-axis current controller 2
4. The frequency integrator 13 and the like constitute the first control means in claim 1, and include the f / V converter 11, the polar coordinate converter 12,
Conventional f / V control means such as the adder 14 and the voltage command calculator 15 constitute the second control means in claim 1. Further, the control switch 26, the changeover switch 25 and the like constitute a changeover means in the first aspect.

Hereinafter, a control method of the synchronous motor 70 at the time of low speed operation will be described. The coordinate converter 22 detects the current detection values i _u , i _w
And the d and q axis currents _id and _iq are calculated based on the phase θ and the phase θ. Current command value Each current regulator 23, 24 i _d ^*, i _q ^* and the current detection value i _d, amplifies the deviation between i _q d, q-axis voltage command v _d ^* (low speed), v _q ^* Calculate (low speed). During low-speed operation, instead of the d and q-axis voltage commands v _d ^* (high speed) and v _q ^* (high speed) calculated by the f / V converter 11, v _d ^* (low speed) via the changeover switch 25 , V _q ^* (slow speed) to the polar coordinate converter 12 to calculate V ^* and φ, and using these and θ, the voltage command calculator 15 causes the three-phase voltage commands v _u ^* , v _v ^* , v The terminal voltage of the motor 70 is controlled by calculating _w ^* .

As means for switching the control according to the high-speed operation and the low-speed operation of the motor 70, the control switch 26 outputs a control switch signal based on the magnitude of the frequency command f ^* via the ramp function, and this signal The switch 25 is driven.

Next, a second embodiment of the present invention will be described with reference to a control block diagram of FIG. This embodiment corresponds to the second embodiment of the present invention. The embodiment of FIG. 2 is obtained by adding the function of a portion surrounded by a chain line to FIG. That is, in the embodiment of FIG. 1, the function of presetting the output of the frequency integrator 13 and the change of the magnitude of the terminal voltage V in order to reduce the shock when switching from the control at the low speed operation to the control at the high speed operation A function to limit the rate is added.

More specifically, a voltage command switch 27 is provided between the polar coordinate converter 12 and the voltage command calculator 15, and a θ preset value, which will be described later, output from the switch 27 is transmitted via a switch 28. It is applied to the frequency integrator 13. Note that a control switching signal from the control switch 26 is applied to the voltage command switch 27 and the frequency integrator 13. Here, the voltage command switch 27 and the frequency integrator 13 constitute the third control means and the limiting means in claim 2.

FIG. 3 is a detailed block diagram of a portion surrounded by a dashed line in FIG. 2. The operation when switching the control mode from low-speed operation to high-speed operation will be described with reference to FIG. It is assumed that the control device is a digital control device that performs sample value control. Further, z ^-1 in the drawing is a function of delaying the state by one sample period in the sample value control and outputting the previous value.

The moment when the control mode is switched from the low-speed operation mode to the high-speed operation mode is detected, and the voltage magnitude V ₀ ^* and the angle φ at the time of the low-speed operation mode immediately before the switching are respectively stored in the first memory 271 and the second memory 271. And these stored signals are referred to as V ₀ ^* (low speed) and φ (low speed). Further, the angle φ in the high-speed operation mode immediately after switching to the high-speed operation mode is stored in the third memory 273,
The stored signal is called φ (high speed). The frequency integrator 13 presets θ to the value of Expression 3 by the output of the voltage command switch 27 immediately after switching the control mode from the low-speed operation mode to the high-speed operation mode.

[0021]

[Equation 3] θ preset value = θz + φ (high speed) −φ (low speed) (previous value of θz = θ)

On the other hand, in the V ^* switch 27 ', the magnitude V ^* of the terminal voltage is calculated by the equation 4 according to the elapsed time t immediately after switching from the low-speed operation mode to the high-speed operation mode.

[0023]

Equation 4] ^{V * = (t / T)} V 0 * + {1- (t / T)} V 0 * ( low speed) (0 <t <T) _{^{or, V * = V 0 * (}} T ≦ t (T: time from control switching, T: time to complete control switching)

With the above function, the phase of the terminal voltage can be made equal before and after the control switching, and the change in the magnitude of the terminal voltage can be made smooth, so that the shock at the time of switching can be reduced.

Next, a third embodiment of the present invention will be described with reference to a control block diagram of FIG. This embodiment corresponds to the third embodiment of the present invention. The embodiment of FIG.
In the embodiment of FIG. 1, when the d and q axis current regulators are PI regulators, this is for reducing the shock when switching from control during high speed operation to control during low speed operation. 1 is obtained by adding a function of presetting the output of the integrator of the d and q axis current controllers.

FIG. 5 is a detailed block diagram of a portion related to control mode switching. d, q-axis current command values _id ^* , i
_q ^* is the low-pass filter 2 of each of the controllers 23 and 24.
Fill in 31,241, amplifies these outputs and d, q-axis current detection value i _d, the deviation between i _q by the proportional gain 1. The results obtained by integrating the outputs of the proportional gains 1 and 2 by the integrators 232 and 242 and the outputs of the proportional gains 1 and 2 are used as d and q-axis voltage commands v _d ^* (low speed) and v _q ^* (low speed).
And

When switching the control mode from the high-speed operation mode to the low-speed operation mode, the d- and q-axis current controllers 23, 24
Are output from the f / V converter 11 as voltage commands v _d ^* (high speed) and v _q ^* (high speed).
Preset to. In addition, d, q-axis current command values _id ^* , i
preset the outputs of the _q ^* of the low-pass filter 231 and 241 current detection value i _d, the i _q. As a result, the magnitude and phase of the terminal voltage can be controlled equally before and after the control switching, and the shock at the time of switching can be reduced.

The fourth embodiment of the present invention is obtained by adding a shock mitigation function at the time of control switching of the second embodiment and the third embodiment to the first embodiment.
Shock at the time of control mode switching can be reduced both during acceleration and deceleration. The control block diagram is omitted.

[0029]

As described above, according to the present invention, the stability of a synchronous motor without a magnetic pole position detector at the time of low speed operation is improved, the upper limit of the outputtable torque is increased, and the acceleration / deceleration time is reduced. There is an effect that it can be shortened.

[Brief description of the drawings]

FIG. 1 is a control block diagram according to a first embodiment of the present invention.

FIG. 2 is a control block diagram according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a main part of FIG. 2;

FIG. 4 is a control block diagram according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a main part of FIG. 4;

FIG. 6 is a control block diagram showing a conventional technique.

FIG. 7 is an explanatory diagram of a voltage vector.

[Explanation of symbols]

Reference Signs List 11 f / V converter 12 polar coordinate converter 13 frequency integrator 14 adder 15 voltage command calculator 16 PWM circuit 21 current detector 22 coordinate converter 23 d-axis current regulator 24 q-axis current regulator 25 switch 26 control Switch 27 Voltage command switch 27 'v ^* Switch 28 Switch 50 Power supply 60 Power converter 70 Permanent magnet synchronous motor 231,241 Low-pass filter 232,242 Integrator 271,272,273 Memory

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahiro Yamazaki 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Nobuo Itoigawa 1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 F term in Fuji Electric Co., Ltd. (reference) 5H576 BB06 BB10 CC05 DD02 DD07 EE01 EE04 EE11 EE19 GG04 GG07 HB01 JJ03 JJ08 JJ11 JJ15 JJ17 JJ22 JJ24 JJ26 JJ28 LL22

Claims (3)

[Claims] 1. A control device for controlling a synchronous motor having no magnetic pole position detector by a power converter, wherein an armature current and a terminal voltage of the synchronous motor are taken as a vector, and a magnitude of the armature current is determined by a current command value. And the first control means for controlling the frequency of the armature current to match the frequency command value; and making the magnitude of the terminal voltage substantially proportional to the frequency command value; A second control means for controlling the power converter to match the frequency command value; a power converter controlled by an output of the second control means when the frequency is high, and an output of the first control means when the frequency is low. A control device, comprising: switching means for switching a control operation to control the power converter. 2. The synchronous motor control device according to claim 1, wherein when switching from the control operation by the first control means to the control operation by the second control means, the phase of the terminal voltage of the synchronous motor is changed before and after the switching. A control device for a synchronous motor, comprising: third control means for performing control so as to be equal to each other; and limiting means for limiting a rate of change in the magnitude of the terminal voltage. 3. The synchronous motor control device according to claim 1, wherein the first control means integrates at least a deviation between the current command value and the current detection value to calculate a terminal voltage command value. When switching from the control operation by the second control means to the control operation by the first control means, the output of the integration element is preset so that the phase and magnitude of the terminal voltage become equal before and after the switching. A first function, a second function of presetting an initial value of the current command value and switching to a control operation by the first control means at a predetermined change rate, or a combination of the first and second functions. A control device for a synchronous motor.