JP3724680B2 - Control method of permanent magnet synchronous motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permanent magnet synchronous motor, and more particularly to a method for controlling a permanent magnet synchronous motor having saliency.
[0002]
[Prior art]
A conventional method for controlling a permanent magnet synchronous motor is disclosed in, for example, Japanese Patent Laid-Open No. 4-101629. This is shown in FIG.
In FIG. 6, (a) is a command current conversion circuit in the conventional control method, in which 10 is a CPU, 11 is a command current calculation means, 12 is a speed calculation means, 13 is a plate width correction coefficient data table, and 14 is A phase correction data table, 51a is a D / A converter, 52a is a phase calculator, and 55 is a programmable timer. In this circuit, a correction phase angle signal θ _d is created from the speed feedback signal by the phase correction data table 14, and a current command is created from the amplitude correction signal and the torque command created by the amplitude correction coefficient data table 13. is there.
[0003]
[Problems to be solved by the invention]
However, in the prior art, as shown in FIG. 6B, the phase angle control starts from a position where the motor rotational speed is not 0. When the phase angle control is 0, the AC m-phase motor having saliency ( Since the reluctance torque component of the IPM motor (hereinafter referred to as IPM motor) cannot be used, the output torque is reduced. Furthermore, the maximum phase control angle (at the maximum rotation speed) is almost 20 degrees, so a wide range of constant output characteristics can be obtained. There was no problem.
The problem to be solved by the present invention is to provide a method for controlling an electric motor capable of performing a wide range of constant output control in an IPM motor.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, a control method for a permanent magnet synchronous generator according to the present invention includes a permanent magnet built in a rotor core, and a q axis that is orthogonal to a d axis inductance L _d that is a direct axis of the permanent magnet. A permanent magnet synchronous motor having a saliency in which the relationship of inductance L _q is L _d <L _q ,
A power unit comprising a converter unit that converts alternating current of the alternating current power source into direct current and an inverter unit that converts direct current converted by the converter unit into a sine wave;
A speed conversion circuit that converts a signal obtained from a speed sensor attached to the permanent magnet synchronous motor into a speed feedback signal;
A speed amplifier that amplifies the deviation between the speed command and the speed feedback signal;
A command current DC / AC conversion circuit for converting a signal obtained from a magnetic pole sensor attached to the speed sensor and the permanent magnet synchronous motor into a two-phase current command signal;
A current amplifier that receives and amplifies the two-phase current command signal output from the command current DC / AC conversion circuit;
A PWM circuit for creating a PWM signal corresponding to the speed deviation from the two-phase output signal output from the current amplifier;
In a control method of a permanent magnet synchronous motor having a control unit composed of a base drive circuit that gives an on / off signal to a base of a transistor constituting an inverter of the power unit from a PWM signal output from the PWM circuit,
A permanent magnet synchronous motor characterized in that a phase angle θ of a two-phase current command signal generated by the command current DC / AC conversion circuit is defined by the following linear function with respect to a rotational speed N of the permanent magnet synchronous motor: Control method.
θ (N) = θ _i + γ · N
θ _i : Phase angle command when N = 0 (phase angle initial value)
γ = (θ _max −θ _i ) / N _max ,
θ _max : Maximum rotational speed phase angle command, N _max : Maximum rotational speed In this control method, the phase angle command θ _i when N = 0 is set to 30 ° ≦ θ _i ≦ 50 °,
Phase angle command θ _max at maximum rotation speed θ _i ≦ θ _max ≦ 90 °
Set to.
Further, in order to accelerate the acceleration characteristic up to the base rotational speed linearly with respect to the time axis, when the motor rotational speed N is 0 ≦ N ≦ N _base ,
θ (N) = θ _base ,
When the motor rotation speed N is N _base <N ≦ N _max
θ (N) = θ _base + γ ′ · N
Where θ _base : phase angle command when 0 ≦ N ≦ N _base ,
γ ′ = (θ _max −θ _base ) / (N _max −N _base ),
θ _max : Phase angle command at maximum rotation speed,
N _max : Maximum rotation speed,
To be.
The phase angle command θ _base is set to 30 ° ≦ θ _base ≦ 50 °, and the phase angle command θ _max at the maximum rotation speed is set to θ _base ≦ θ _max ≦ 90 °.
[0005]
In this way, by changing the phase angle command θ with a positive gradient γ according to the rotational speed of the permanent magnet synchronous motor, field weakening control of the permanent magnet synchronous motor becomes possible, and permanent magnet synchronous motor terminal voltage saturation is suppressed. Control up to the high-speed rotation range is possible. In addition, the reluctance torque of the IPM motor can be effectively used by setting the phase angle command initial value θ _i in the range of “30 ° ≦ θ _i ≦ 50 °”.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 3, the motor to be controlled has a permanent magnet 14 in the rotor core 13 and has a saliency in which the relationship between the d-axis inductance L _d and the q-axis inductance L _q is L _d <L _q. It is an IPM motor having. The basic configuration of the motor driver (drive device) is as shown in FIG. That is, a speed feedback of a signal obtained from a power unit 3 including a converter unit 1 that converts alternating current of an AC power source into direct current and an inverter unit 2 that converts the converter into a sine wave, and a speed sensor 4 attached to the motor. A signal obtained from a speed conversion circuit 5 for converting to a signal, a speed amplifier 6 for amplifying a deviation between the speed command and the speed feedback signal, and a signal obtained from the speed sensor 4 and the magnetic pole sensor 7 attached to the motor is converted into a current command. A command current DC / AC conversion circuit 8, a current amplifier 9 that receives and amplifies this signal, a PWM circuit 10 that creates a PWM signal from this amplified signal, and a base that provides an on / off signal from the PWM signal to the base of a transistor A control unit 15 including a drive circuit 11 is included.
[0007]
In the command current DC / AC conversion circuit 8, there is a current distribution signal generator 12, and each phase current signal generated from this is as follows.
I _U ^* = K · cos θ θ: phase angle I _V ^* = K · cos (θ + 2 / 3π) K: When a proportionality constant is calculated and output, the phase angle command θ is set to 0 when the rotational speed is 0 with respect to the motor rotational speed. The phase angle command initial value θ _i is changed with a positive gradient γ up to the maximum rotation speed N _max . If this is expressed in a function expression,
θ (N) = θ _i + γ · N = θ _i + {(θ _max −θ _i ) / N _max } · N
Where N: motor rotation speed, θ _max : phase angle command at maximum rotation speed γ = (θ _max −θ _i ) / N _max
Then, the motor is controlled along this equation. Further, the phase angle command initial value θ _{i is set} to 30 ° ≦ θ _i ≦ 50 °.
Here, θ _i = 45 ° is determined. Furthermore, the maximum rotational speed phase angle command θ _max is
θ _i ≦ θ _max ≦ 90 °
In this case, θ _max = 75 ° is determined.
Here, the reason for θ _i = 45 ° is that the maximum torque point of the motor in which the magnet torque T _m and the reluctance torque T _r are combined is around θ = 45 °, as can be seen from the phase-torque characteristics of FIG. It becomes. Therefore, from 0 rotation to N _base requires the most torque, so θ _i = 45 ° is set.
The reason why θ _max = 75 ° is optimal is that, in the characteristics of the constant output region, it is necessary to keep the motor terminal voltage below the allowable maximum voltage. Therefore, the motor phase angle control is further performed with θ _i > 45 °. Control in the lead phase is required. The reason that θ _max = 75 ° is good is that when a constant output characteristic of 1: 3 is assumed, the phase becomes the most efficient at the maximum rotation speed N _max .
[0008]
FIG. 2 is an output characteristic diagram of the motor according to the first embodiment of the present invention. As shown in the figure, the phase angle θ changes with a linear function with respect to the rotational speed N. For example, if θ _i = 45 °, θ _max = 75 °, and N _max = 4500 rpm,
θ (N) = 45 ° + 6.67 × 10 ⁻³ N
It becomes. As a result, when the maximum rotation speed at which the torque is constant with respect to the rotation speed is the base rotation speed N _base and the maximum rotation speed at which the output is constant with respect to the rotation speed is the maximum rotation speed N _max , N _base : N A constant output characteristic with _max , that is, a constant output ratio of about 1: 3 is obtained.
[0009]
As a second embodiment, the phase angle command θ is
1) When the motor rotation speed N is 0 ≦ N ≦ N _base ,
θ (N) = θ _base
2) When the motor rotation speed N is _Nbase <N ≦ _Ntop ,
θ (N) = θ _base + γ ′ · N
Where θ _base : phase angle command when 0 ≦ N ≦ N _base ,
γ ′ = (θ _max −θ _base ) / (N _max −N _base ),
θ _max : Phase angle command at maximum rotation speed,
N _max : Maximum rotation speed,
To be.
The phase angle command θ _base is set to 30 ° ≦ θ _base ≦ 50 °, and the phase angle command θ _max at the maximum rotation speed is set to θ _base ≦ θ _max ≦ 90 °. The reason is that when the phase-torque characteristics of FIG. 4 are viewed, there is not much difference in torque in the range of 30 ° ≦ θ _base ≦ 50 °. In addition, as described above, in the constant output region, θmax becomes a phase that is further advanced than θbase, so θ _base ≦ θ _max and the maximum phase control range is 90 °, so that θ _max ≦ 90 ° is set. It is.
[0010]
FIG. 5 is an output characteristic diagram of the motor of the second embodiment of the present invention. As shown in the figure, the phase angle command θ changes with the following function with respect to the rotational speed N. For example, if θ _base = 45 °, N _base = 1500 rpm, θ _max = 75 °, N _max = 4500 rpm, the range of the motor rotation speed N from 0 ≦ N ≦ 2500 rpm is
θ (N) = 45 °,
The range where the motor rotation speed N is 2500 <N ≦ 7500 rpm is
θ (N) = 45 ° + 15 × 10 ⁻³ × N
It becomes. As a result, when the maximum rotation speed at which the torque is constant with respect to the rotation speed is the base rotation speed N _base and the maximum rotation speed at which the output is constant with respect to the rotation speed is the maximum rotation speed N _max , N _base : N A constant output characteristic with _max , that is, a constant output ratio of about 1: 3 is obtained. Furthermore, the characteristic of the constant torque region is constant compared to the case of the first embodiment.
[0011]
【The invention's effect】
As described above, according to the present invention, the reluctance torque can be most effectively used in the constant torque region up to the base rotational speed N _base by changing the phase angle command θ with a linear function with respect to the rotational speed N. It can be controlled with the optimum phase angle, and field-weakening control is performed in the constant output region where the voltage is saturated, so that a wide range of constant output control of the IPM motor can be performed. Further, by changing the phase angle command before and after the base rotational speed, the constant torque characteristics are improved, so that the linear acceleration characteristics up to the base rotational speed required when used for a solid type spindle can be obtained.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of a motor driver (drive circuit) according to an embodiment of the present invention.
FIG. 2 is an output characteristic diagram of a motor according to an embodiment of the present invention.
FIG. 3 is an explanatory view showing a rotor structure of a motor (IPM motor) used in an embodiment of the present invention.
FIG. 4 is a characteristic diagram showing phase-torque characteristics of a motor used in an embodiment of the present invention.
FIG. 5 is an output characteristic diagram of a motor according to a second embodiment of the present invention.
FIG. 6 is a block diagram showing a conventional driving method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Converter part, 2 Inverter part, 3 Power part, 4 Speed sensor, 5 Speed conversion circuit, 6 Speed amplifier, 7 Magnetic pole sensor, 8 Command current DC / AC conversion circuit, 9 Current amplifier, 10 PWM circuit, 11 Base drive circuit , 12 current distribution signal generator, 13 rotor core, 14 field permanent magnet, 15 controller

Claims (4)

A permanent magnet is provided in a rotor core and has a saliency in which the relationship between the d-axis inductance L _d that is the direct axis of the permanent magnet and the q-axis inductance L _q that is the orthogonal axis is L _d <L _q. An electric motor,
A power unit comprising a converter unit that converts alternating current of the alternating current power source into direct current and an inverter unit that converts direct current converted by the converter unit into a sine wave;
A speed conversion circuit that converts a signal obtained from a speed sensor attached to the permanent magnet synchronous motor into a speed feedback signal;
A speed amplifier that amplifies the deviation between the speed command and the speed feedback signal;
A command current DC / AC conversion circuit for converting a signal obtained from a magnetic pole sensor attached to the speed sensor and the permanent magnet synchronous motor into a two-phase current command signal;
A current amplifier that receives and amplifies the two-phase current command signal output from the command current DC / AC conversion circuit;
A PWM circuit for creating a PWM signal corresponding to the speed deviation from the two-phase output signal output from the current amplifier;
In a control method of a permanent magnet synchronous motor having a control unit composed of a base drive circuit that gives an on / off signal to a base of a transistor constituting an inverter of the power unit from a PWM signal output from the PWM circuit,
A permanent magnet synchronous motor characterized in that a phase angle θ of a two-phase current command signal generated by the command current DC / AC conversion circuit is defined by the following linear function with respect to a rotational speed N of the permanent magnet synchronous motor: Control method.
θ (N) = θ _i + γ · N
Here, θ _i : phase angle command when N = 0,
γ = (θ _max −θ _i ) / N _max ,
θ _max : Phase angle command at maximum rotation speed,
N _max : Maximum rotation speed The phase angle command θ _i when N = 0 is 30 ° ≦ θ _i ≦ 50 °,
Phase angle command θ _max at maximum rotation speed θ _i ≦ θ _max ≦ 90 °
The method for controlling a permanent magnet synchronous motor according to claim 1, wherein: When the maximum rotation speed at which the torque is constant with respect to the motor rotation speed is defined as the base rotation speed N _base , the phase angle command expressed as a function with respect to the rotation speed N of the permanent magnet synchronous motor is:
1) When the motor rotation speed N is 0 ≦ N ≦ N _base ,
θ (N) = θ _base ,
2) When the motor rotation speed N is N _base <N ≦ N _max
θ (N) = θ _base + γ ′ · N
Where θ _base : phase angle command when 0 ≦ N ≦ N _base ,
γ ′ = (θ _max −θ _base ) / (N _max −N _base ),
θ _max : Phase angle command at maximum rotation speed,
N _max : Maximum rotation speed,
The method for controlling a permanent magnet synchronous motor according to claim 1, wherein: 4. The permanent magnet according to claim 3, wherein the phase angle command θ _base is set to 30 ° ≦ θ _base ≦ 50 °, and the phase angle command θ _max at the maximum rotation speed is set to θ _base ≦ θ _max ≦ 90 °. Control method of synchronous motor.

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