JP2000232798A - Control method for synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a control for synchronous motor being supplied with power from a power conversion circuit in which start characteristics can be enhanced when vector control is performed only through a speed sensor for the motor, i.e., an incremental encoder. SOLUTION: A control circuit comprises a current command operating unit 11, multipliers 12, 13, and a sine wave oscillator 18 and a reluctance torque is generated in a synchronous. motor 3, when it is started, by controlling the output from the multiplier 12, i.e., the d-axis current command value id*, and the output from the multiplier 13, i.e., the q-axis current command value iq*, to be in-phase or reverse phase AC currents having a same amplitude. The synchronous motor 3 is accelerated with that torque until an origin signal is generated from an incremental encoder 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a synchronous motor supplied by a power conversion circuit.

[0002]

2. Description of the Related Art When performing variable speed control of a permanent magnet type synchronous motor as a commonly used synchronous motor supplied by a power conversion circuit by vector control, an incremental signal and an origin signal from a speed sensor of the motor are used. In addition, the position information of the rotor of the permanent magnet synchronous motor is required.

For this purpose, an absolute encoder or a resolver capable of simultaneously obtaining the incremental signal, the origin signal and the position information is provided, or the speed sensor and a magnetic pole position sensor for obtaining the position information are provided.

[0004]

The above-described absolute encoder and resolver are more expensive than the incremental encoder serving as the speed sensor, and are not provided with the incremental encoder and the magnetic pole position sensor. And expensive,
There was a drawback that it became large.

However, when the synchronous motor is controlled at a variable speed by vector control using only the incremental encoder, as is well known, the motor is started and the accurate position of the rotor of the motor is maintained until the encoder generates an origin signal. It is difficult to obtain information, and as a result, at the time of starting immediately after turning on the power, the motor rotates reversely until the origin signal is generated, operation becomes impossible due to insufficient starting torque, and the acceleration time even after starting is increased. There were problems such as lengthening.

As a countermeasure against the above-mentioned problem, various methods have been proposed for estimating the position information using, for example, the saliency of a permanent magnet type synchronous motor. There was also a problem that it was difficult to determine the pole. An object of the present invention is to provide a control method for a synchronous motor that solves the above problems.

[0007]

According to a first aspect of the present invention, there is provided a synchronous motor which is supplied with electric power by a power conversion circuit. The motor is controlled by vector control based on an incremental signal from a speed sensor of the motor and an origin signal. In the method for controlling a synchronous motor that performs variable speed control, the d-axis current and the q-axis current of the motor are controlled by the vector control during the period when the motor is started and until the origin signal is generated. A control method is characterized in that alternating currents having the same amplitude and the same phase or opposite phases are used.

According to a second aspect of the present invention, in the synchronous motor control method according to the first aspect, when the speed command of the motor is positive, the d-axis current and the q-axis current are equal in amplitude. And alternating currents of opposite phases,
When the speed command of the motor is negative, the d-axis current and the q-axis current are alternating currents having the same amplitude and the same phase.

In a third aspect of the present invention, in the method for controlling a synchronous motor according to the first aspect of the invention, when the torque command of the motor has a positive polarity, the d-axis current and the q-axis current are equal to each other. And, as alternating currents of opposite phases to each other, and when the torque command of the motor is negative, the d-axis current and the q-axis current are equal in amplitude,
In addition, AC currents having the same phase are used.

According to the present invention, the d-axis current and the q-axis current based on the vector control of the synchronous motor are used as the respective alternating currents, so that the rotor of the motor generates an alternating magnetic field in a desired direction. Attention is paid to the reluctance torque generated by the asymmetry of the magnetic circuit of the electric motor, and the reluctance torque is positively used to start the electric motor.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of a synchronous motor control method according to the present invention, wherein 1 is a power conversion circuit formed by connecting semiconductor switch elements in a three-phase bridge. A current detector for detecting an output current of the power conversion circuit 1, a synchronous motor 3 fed from the power conversion circuit 1 via the current detector 2, 4 an incremental encoder as a speed sensor of the synchronous motor 3, 5 a synchronous motor Electric motor 3
A speed setting device for setting the speed command value (ω ^* ) of the speed detector 10 and a speed command value (ω ^* ) from the speed setting device 5 and the current detector 2
Signal for controlling the variable speed of the synchronous motor 3 by the vector control based on the detection values (iu, iw) from the control signals and the A-phase incremental signal, the B-phase incremental signal, and the origin (Z-phase) signal from the incremental encoder 4. Is transmitted to each of the semiconductor switch elements of the power conversion circuit 1.

FIG. 2 shows a method for controlling a synchronous motor according to the present invention.
Of the control device 10 shown in FIG. 1 showing the first embodiment of the present invention.
FIG. 3 is a detailed circuit configuration diagram. That is, the details of the part shown in FIG.
The circuit includes a torque finger, which is the output of a speed controller (not shown).
Command value τ^*From the current command value I allowed by the power conversion circuit 1^*
And a multiplication operation unit 12, 1
3 and a d-axis current command value id which is an output of the multiplication operation unit 12
^*And detection from the current detector 2 obtained by the coordinate converter 14
The values iu and iw are represented by position data from a magnetic pole position calculator (not shown).
Calculated value θ_ESTD-axis current detection value id which is coordinate-converted based on
A d-axis current controller 15 that performs an adjustment operation based on the deviation of
Q-axis current command value iq which is the output of multiplication operation unit 13^*And zodiac
Detected value i from the current detector 2 obtained by the target converter 14
The deviation from the q-axis current detection value iq obtained by transforming u and iw
A q-axis current controller 16 for performing an adjustment operation based on
D-axis voltage command value vd which is the output of controller 15^*And q-axis
Q-axis voltage command value vd which is the output of the flow controller 16 ^*And before
Position calculation value θ from magnetic pole position calculator_ESTCoordinates based on
Converted U-phase voltage command value vu^*, V-phase voltage command value v
v^*, W-phase voltage command value vw^*Coordinate converter 17 that outputs
And a sine wave signal having a predetermined amplitude and frequency is generated.
A sine wave oscillator 18 that outputs a sine wave signal to the multiplication operation unit 13
And the polarity of the sine wave signal is inverted.
And an inverting amplifier 19 that outputs a wave signal to the multiplication operation unit 12.
Have.

The U-phase voltage command value vu ^* , V-phase voltage command value vv ^* , and W-phase voltage command value vw ^* are each subjected to pulse width modulation (PWM) to become the drive signal.
Each of the control elements, such as the reference numerals 11 to 19 described above,
It is formed by a well-known technique.

Power conversion circuit 1 and control circuit 1 shown in FIG.
0, the power is turned on, and in the circuit of the first embodiment shown in FIG. 2, the N-pole direction of the rotor of the synchronous motor 3 is the d-axis, and the direction 90 ° (electrical angle) ahead of the d-axis is q. The operation when the synchronous motor 3 is started by this circuit will be described below. Assuming that the sine wave signal output from the sine wave oscillator 18 is sinω _h t, the d-axis current command value i
The d ^* and the q-axis current command value iq ^* are expressed by Expressions (1) and (2).
It is represented by

[0015]

## EQU1 ## id ^* =-I ^* sin ω _h t (1)

[0016]

Eq ^* = I ^* sin ω _h t (2) The output voltage of the power conversion circuit 1, that is, the terminal voltage of the synchronous motor 3, by id ^* and iq ^* shown in the above equations (1) and (2). Is controlled, id ^* = the above id, iq ^*
= Iq. As a result, the current vibrates on the vector locus shown in FIG. 3 and an alternating magnetic field is generated.

By the way, the torque and the current of the permanent magnet type synchronous motor having the embedded magnet structure as the synchronous motor 3 have a relation of the equation (3).

[0018]

Equation 3] _{τ = P {ψ m iq +} (L d -L q) id · iq} ... (3) where, tau: torque, L _d, L _{q: d-axis,} q-axis inductance, [psi _m: No Load linkage flux, P: number of pole pairs.

By substituting equations (1) and (2) into equation (3), equation (4) is obtained.

[0020]

Equation 4] tau = P - right-hand side of ^{_{{ψ m I * sinω h t}} (1/2) (L d -L q) I * 2 (1-cos2ω h t)} ... (4) the formula (4) The first term is the magnet torque, and the second term on the right side is the reluctance torque. Although the average value of this magnet torque is zero, since the reluctance torque includes a DC component, a torque is generated as this average value, and this torque is expressed by equation (5).

[0021]

Τ = − (P / 2) (L _d −L _q ) I ^{* 2} (5) The polarity of the torque τ represented by the above equation (5) is only the magnitude relation between the L _d and L _q. Depends on. Therefore, even when the polarity of the rotor position is unknown, a torque of the same polarity is always generated, and in the above-described permanent magnet type synchronous motor, generally, L _d <L.
_Because of the relationship of _q , a positive torque is always generated.

That is, when the synchronous motor 3 is started and the origin (Z
During the period (maximum one rotation) until the signal (phase) is generated, the synchronous motor 3 is accelerated by the torque shown in the above equation (5), and after the origin (Z phase) signal is generated, The phase operation value θ _EST is corrected to a normal value by the phase) signal, and the current command operation unit 11 and the multiplication operation units 12 and 13 are adjusted from the torque command value τ ^* to the normal d-axis current command value id ^{*. *} D-axis current command calculator for calculating ^* , and normal q-axis current command value i
By replacing it with a q-axis current command calculator that calculates q ^** , smooth start and acceleration without reverse rotation can be achieved.
The acceleration time can be reduced.

FIG. 4 is a partially detailed circuit configuration diagram of a control device 10 shown in FIG. 1 showing a second embodiment of the control method of the synchronous motor according to the present invention, which is the same as the embodiment circuit shown in FIG. Those having functions are denoted by the same reference numerals and description thereof will be omitted.

That is, the partial detailed circuit shown in FIG.
Flow command operation unit 11, multiplication operation unit 12, multiplication operation unit 13,
Coordinate converter 14, d-axis current controller 15, q-axis current controller
16, coordinate converter 17, sine wave oscillator 18, and velocity
Speed command value ω from setting device 5 ^*Code detection to determine the polarity of
Output unit 20 and the polarity (± 1) output by sign detector 20
The output polarity of the sine wave oscillator 18 is changed based on the
The output of the sine wave oscillator 18 is in phase with the
Has a multiplying operation unit 21 for outputting a sine wave signal having an opposite phase.
I have.

The power conversion circuit 1 and the control circuit 1 shown in FIG.
0, the power is turned on, and in the circuit of the second embodiment shown in FIG. 4, the N-pole direction of the rotor of the synchronous motor 3 is the d-axis, and the direction 90 ° (electrical angle) ahead of the d-axis is q. The operation when the synchronous motor 3 is started by this circuit will be described below. At this time, the d-axis current command value id ^* , which is the output of the multiplication operation unit 12, is represented by Expression (6).

[0026]

[6] _{^{id * = -I * sinω h t}} (ω * ≧ 0) _{^{or, id * = I * sinω h}} t (ω * <0) ... (6) the formula (2), by the formula (6) By controlling the output voltage of the power conversion circuit 1, that is, the terminal voltage of the synchronous motor 3, by the indicated id ^* and iq ^* , id ^* = id, iq ^*
= Iq. As a result, the current oscillates on different vector trajectories depending on the polarity of ω ^* as shown in FIG. 5, and an alternating magnetic field is generated. As a result, since the reluctance torque includes a DC component, a torque is generated as an average value of the reluctance torque, and this torque is represented by Expression (7).

[0027]

[Equation 7] τ = - (P / 2) (L d -L q) I * 2 (ω * ≧ 0) or, τ = (P / 2) (L d -L q) I * 2 (ω * the polarity of the torque τ indicated by <0) ... (7) the equation (7) depends only on the magnitude relation of the L _d and L _q. In the above-described permanent magnet type synchronous motor, since L _d <L _q is generally _satisfied , ω ^*
Torque in the same direction as the polarity of

That is, when the synchronous motor 3 is started and the origin (Z
During the period (maximum one rotation) until the signal (phase) is generated, the synchronous motor 3 is accelerated in the direction based on the ω ^* with the torque shown in the equation (7), and the origin (Z phase) signal is generated. Thereafter, the position calculation value θ _EST is obtained by the origin (Z phase) signal.
Is corrected to a normal value, and the current command calculator 11 and the multiplying calculators 12 and 13 calculate the normal d-axis current command value id ^** from the torque command value τ ^* . And a q-axis current command calculator for calculating a normal q-axis current command value iq ^** , so that a smooth start,
Can accelerate.

FIG. 6 is a partial detailed circuit configuration diagram of the control device 10 shown in FIG. 1 showing a third embodiment of the control method of the synchronous motor according to the present invention, and is the embodiment shown in FIGS. Components having the same functions as the circuits are denoted by the same reference numerals and description thereof will be omitted.

That is, the partial detail circuit shown in FIG. 6 includes a multiplication operation unit 12, a multiplication operation unit 13, a coordinate conversion unit 14, a d-axis current adjustment unit 15, a q-axis current adjustment unit 16, and a coordinate conversion unit 1.
7, a sine wave oscillator 18, a multiplication operation unit 21, a current instruction operation unit 22 replacing the current instruction operation unit 11, and a sign detector 23 for determining the polarity of the torque instruction value τ ^* .

The power conversion circuit 1 and the control circuit 1 shown in FIG.
0, the power is turned on, and in the circuit of the third embodiment shown in FIG. 6, the N-pole direction of the rotor of the synchronous motor 3 is the d-axis, and the direction 90 ° (electrical angle) ahead of the d-axis is q. The operation when the synchronous motor 3 is started by this circuit will be described below. The current command calculator 22 calculates the current command value I ^* from the torque command value τ ^* by performing the calculation shown in Expression (8).

[0032]

Equation 8] I ^* = {| 2τ ^* / [P (L _d -L _q)] |} ^1/2 ... (8) polarity sign detector 23 outputs (± 1) to basis of the sine wave oscillator 18 The polarity of the output is changed. At this time, the d-axis current command value id ^* , which is the output of the multiplying operation unit 12, is calculated by the equation (9).
It is represented by

[0033]

[Equation 9] _{^{id * = -I * sinω h t}} (τ * ≧ 0) _{^{or, id * = I * sinω h}} t (τ * <0) ... (9) the formula (2), by the formula (9) By controlling the output voltage of the power conversion circuit 1, that is, the terminal voltage of the synchronous motor 3, by the indicated id ^* and iq ^* , id ^* = id, iq ^*
= Iq. As a result, the current vibrates on different vector trajectories depending on the polarity of τ ^* as shown in FIG. 5, and an alternating magnetic field is generated.

As a result, even when the polarity of the magnetic pole of the rotor is unknown, a torque τ corresponding to the torque command value τ ^* is generated, and the polarity of the torque τ is generally L _{d in the} aforementioned permanent magnet type synchronous motor. < _Lq , torque is generated in the same direction as the polarity of τ ^* .

That is, when the synchronous motor 3 is started and the origin (Z
During the period (maximum one rotation) until the signal (phase) is generated, the synchronous motor 3 is accelerated in the direction based on the τ ^* with the torque shown in the equation (7), and the origin (Z phase) signal is generated. Thereafter, the position calculation value θ _EST is obtained by the origin (Z phase) signal.
Is corrected to a normal value, and the current command calculator 22 and the multiplication calculators 12 and 13 are adapted to calculate a normal d-axis current command value id ^** from the torque command value τ ^* . And a q-axis current command calculator for calculating a normal q-axis current command value iq ^** , so that a smooth start,
Can accelerate.

[0036]

According to the present invention, the d-axis current and the q-axis current based on the vector control of the synchronous motor based on the incremental signal from the speed sensor of the synchronous motor and the origin signal are the above-described respective AC currents. Thus, the rotor of the electric motor can generate an alternating magnetic field in a desired direction and start the electric motor. As a result, the cost of the drive system can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a partial detailed circuit configuration diagram of FIG. 1 showing a first embodiment of the present invention;

FIG. 3 is a characteristic diagram showing the operation of FIG. 2;

FIG. 4 is a partial detailed circuit configuration diagram of FIG. 1 showing a second embodiment of the present invention;

FIG. 5 is a characteristic diagram showing the operation of FIG. 4;

FIG. 6 is a partially detailed circuit configuration diagram of FIG. 1 showing a third embodiment of the present invention;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1: Power conversion circuit, 2: Current detector, 3: Synchronous motor,
4: Incremental encoder, 5: Speed setting device, 1
0: control device, 11: current command calculator, 12, 13: multiplication calculator, 14: coordinate converter, 15: d-axis current controller,
16: q-axis current controller, 17: coordinate converter, 18: sine wave oscillator, 19: inverting amplifier, 20: sign detector, 21
... Multiplication calculator, 22. Current command calculator, 23. Sign detector.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yama ▲ Saki ▼ Takahiro 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Hiroaki Hayashi Arata Tanabe, Kawasaki-ku, Kawasaki-shi, Kanagawa Field No. 1 Fuji Electric Co., Ltd. F-term (reference) 5H560 BB04 BB12 DA07 DB07 DC12 EB01 EC01 EC10 GG01 HA09 HA10 RR10 XA02 XA04 XA12 XA13 5H576 BB10 DD02 DD07 EE01 EE11 FF01 GG02 GG04 HB01 KK02 LL07 LL07 LL07

Claims (3)

[Claims] 1. A method for controlling a synchronous motor which is fed by a power conversion circuit, wherein the motor is controlled at a variable speed by vector control based on an incremental signal from a speed sensor of the motor and an origin signal. When the motor is started and during the period until the origin signal is generated, the d-axis current and q of the motor by the vector control
A method of controlling a synchronous motor, wherein the shaft currents are AC currents having the same amplitude or the same phase or opposite phases with each other. 2. The method of controlling a synchronous motor according to claim 1, wherein when the speed command of the motor is positive, the d-axis current and the q-axis current are equal in amplitude and opposite to each other. Synchronous, wherein when the speed command of the electric motor is negative, the d-axis current and the q-axis current are alternating currents having the same amplitude and the same phase as each other. Motor control method. 3. The method of controlling a synchronous motor according to claim 1, wherein when the torque command of the motor is positive, the d-axis current and the q-axis current are equal in amplitude and opposite to each other. Wherein the d-axis current and the q-axis current have the same amplitude and are in phase with each other when the torque command of the motor is negative. Motor control method.