JP2000050697A - Control device for synchronous motor - Google Patents

Abstract

(57) Abstract: A synchronous motor control device capable of preventing a load angle δ from approaching an unstable region (around 90 degrees) and stably operating without a decrease in torque is realized. A δ suppressor 19 for controlling an exciting current Im on an M-axis is provided based on a set value of a load angle δ, a magnetic flux value, and a torque current value, so that δ is controlled to be suppressed in a stable region. [Effect] The stable operation of the synchronous motor is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor control device, and more particularly to a synchronous motor control for controlling a magnetic flux and a torque of a motor with high precision.

[0002]

2. Description of the Related Art In vector control of a synchronous motor, the M and T axes of a rotating magnetic field coordinate rotated from the d and q axes of a rotating magnetic pole coordinate by a load angle δ are used as reference coordinates to determine the exciting current component of the motor current and Controls the torque current component.

Here, it is assumed that the MT axis is selected so that the T-axis component φt of the magnetic flux Φ becomes zero, that is, the M axis coincides with the direction of the magnetic flux. At this time, since the armature interlinkage magnetic flux Φ exists only on the M axis, Φ = φm, and the magnitude of the magnetic flux is controlled by controlling φm. When the magnetic flux is constant, the torque is proportional to the T-axis component It of the armature current. Therefore, the torque is controlled by controlling It. By setting the M-axis component Im of the armature current to zero, the magnetic flux and the current are orthogonal (Φ 直交 I), and the power factor of the motor can be controlled to 1. The relationship between the coordinate axes at this time is shown in FIG.

When the synchronous motor is driven by vector control, the load angle δ changes depending on the magnitude of the load, and the range in which the synchronous motor can be driven stably is when the load angle δ is −90 degrees <
It has been found that δ <90 degrees. Here, especially when the load suddenly changes in the field weakening region, there is a problem that the load angle of the synchronous motor exceeds the stable range transiently and becomes uncontrollable. In the apparatus, when a δ estimated value δ ＾ is obtained by control calculation, a limiter circuit is provided to limit δ ＾ to a set value or less to prevent instability (magnetic flux and torque reduction). However, in this method, when δ ＾ is limited by the limiter set value, vector control becomes incomplete, and there is a problem of magnetic flux fluctuation (reduction) and torque reduction. Further, if the synchronous motor is designed to reduce the δ value, there is a problem that the motor becomes large.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the conventional method and to obtain a control device capable of operating a synchronous motor stably. It aims at miniaturization of.

[0006]

According to the control device of the present invention, the maximum value of the load angle δ is arbitrarily set, and when δ that changes from the magnetic flux and torque current conditions exceeds the set value, the magnetic flux value By controlling the exciting current Im on the M axis based on the torque current value, the load angle δ is suppressed to a predetermined value or less, so that the synchronous motor can be stably operated. In addition, since the maximum value of δ can be set arbitrarily, it is possible to remove restrictions on motor design regarding δ.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of a synchronous motor variable speed system according to an embodiment of the present invention. In FIG. 1, 1 is a speed command generator, 2 is a speed controller, 3 is a magnetic flux command calculator,
4 is a field command calculator for controlling magnetic flux by a field current, 5
Is an armature current controller, 6 is a field current controller, 7 is a magnetic flux observer for detecting a motor magnetic flux and a load angle δ, 8, 9 are coordinate converters between the MT axis and the dq axis, and 10 and 11 are dq axes. Converters between the axis and the uvw axis, 12 and 13 are power converters, 1
4 is an armature current detector, 15 is a field current detector, 16 is an armature voltage detector, 17 is a synchronous motor, 18 is a speed / position detector of the synchronous motor 17, and 19 is added according to the present invention. This is a δ suppressor that suppresses the load angle δ by controlling the exciting current Im based on the magnetic flux value and the torque current value. Next, an outline of the operation will be described. First, the rotation speed of the synchronous motor 17 is detected by the speed / position detector 18, and a deviation from the speed command from the speed command generator 1 is added to the speed controller 2, whereby the rotation speed matches the speed command. Is controlled. A current control loop is provided inside the speed control loop as shown in FIG. 1, and the armature current and the field current are detected by the armature current detector 14 and the field current detector 15. The armature current controller 5 and the field current controller 6 control the armature current and the field current to match the respective command values. MT
In order to perform vector control using coordinates, it is necessary to detect the load angle δ and the magnetic flux Φ on the M axis. These are detected by the magnetic flux observer 7 from the armature current and the armature voltage to estimate the motor magnetic fluxes φd and φq, and are calculated using the estimated magnetic fluxes. The calculated δ estimation value is used for the coordinate converters 8 and 9. The magnetic flux Φ is calculated by the magnetic flux observer 7, the deviation between the output of the magnetic flux command calculator 3 and the calculated value is added to the field command calculator 4, and the magnetic field Φ is calculated in accordance with the output field current command If *. The current is controlled.

Conventionally, when the δ suppressor 19 of FIG. 1 is not provided, δ becomes 90 when the torque increases in the field weakening region.
It grows to near degree. FIG. 3 shows a vector diagram at this time. According to FIG. 3, since the magnetic flux and the d-axis (field current) are substantially orthogonal to each other in this state, the magnetic flux cannot be sufficiently controlled by the field control. For this reason, the magnetic flux tends to fluctuate due to the torque fluctuation, which tends to cause a decrease in torque.

Next, the δ suppressor 19 which is a feature of the present invention is described.
Will be described. FIG. 4 shows a vector diagram when the present invention is applied. The principle of the present invention is to suppress the increase in δ by controlling the M-axis current Im to be negative.
The relational expression of the q-axis magnetic flux φq when the M-axis current Im is applied is:

[0011]

(1) φ _q = L _q I _q = L _q (sin δ × I _m + cos δ × I _t ) = Φ sin δ (Equation 1)

[0012]

(Equation 2)

It can be seen that the load angle δ can be controlled by the exciting current Im. Focusing on this, the maximum value δ ~ of the load angle δ that can be operated stably is set arbitrarily, and in a region where δ exceeds this, the set value δ ~, the torque current detection value It ＾, and the magnetic flux detection value Φ ＾

[0014]

(Equation 3)

By flowing the exciting current Im * calculated by the equation (the calculated value is on the negative side), δ can be suppressed to a stable set value δ ~, and a steady control system can be stabilized. Becomes

Next, another embodiment of the present invention will be described with reference to FIG.

In the figure, part numbers 1 to 19 are the same as those of FIG. FIG. 1 shows that the dq-axis current command is directly output by the arithmetic processing in the speed controller.
The difference is that a correction amount is added to the dq-axis current command instead of controlling the excitation current Im based on the magnetic flux value and the torque current value for stabilizing the control system. The correction amount can be easily obtained by performing coordinate conversion of the excitation current Im to dq, and the same effect as in FIG. 1 can be obtained.

Next, another embodiment of the present invention will be described with reference to FIG.

In the drawing, part numbers 1 to 19 are the same as those having the same numbers in FIG. The difference from FIG. 1 is that instead of controlling the excitation current Im based on the magnetic flux value and the torque current value,
When the detected value of the load angle δ exceeds the set value δ ~ set by the δ setting device 20, the deviation between δ ~ which is the output of the δ setting device and the δ detection value δ ＾ which is the output of the magnetic flux observer 7 is calculated. Although the difference is that the excitation current Im is controlled based on this, the δ suppression effect similar to that of FIG. 1 can be obtained.

Next, another embodiment of the present invention will be described with reference to FIG.

In the drawing, part numbers 1 to 20 are the same as those having the same numbers in FIG. The difference from FIG. 6 is that the dq-axis current command is directly output by the arithmetic processing in the speed controller, and when the detected δ value exceeds the set value δ ~, the output of the δ setter δ ~ and the magnetic flux The difference is that a correction amount is added to the dq-axis current instead of controlling the excitation current Im based on the deviation from the δ detection value δ ＾ which is the output of the observer 7. The correction amount can be easily obtained by performing coordinate conversion of the excitation current Im to dq, and an effect similar to that of FIG.

[0022]

As described above, according to the present invention, the synchronous motor can be operated stably by suppressing the load angle δ to a predetermined value or less. Further, since the maximum value of δ can be arbitrarily limited, the overload range of the synchronous motor can be expanded. Further, since there is no restriction on the motor design regarding δ, the motor can be designed at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram of a synchronous motor variable speed control system according to an embodiment of the present invention.

FIG. 2 is a vector diagram for explaining the operation of the synchronous motor (an explanatory diagram showing a relationship between rotor coordinates (dq axes) and magnetic flux coordinates (MT axes)).

FIG. 3 is a vector diagram of the synchronous motor under load.

FIG. 4 is a vector diagram illustrating the operation of the present invention.

FIG. 5 is a block diagram of a synchronous motor variable speed control system according to another embodiment of the present invention.

FIG. 6 is a block diagram of a synchronous motor variable speed control system according to another embodiment of the present invention.

FIG. 7 is a block diagram of a synchronous motor variable speed control system according to another embodiment of the present invention.

[Explanation of symbols]

4 ... field command calculator, 17 ... synchronous motor, 19 ... delta suppressor, 20 ... delta setting device.

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Claims (4)

[Claims] 1. A synchronous motor control device for controlling a synchronous motor by converting a current of the synchronous motor into a torque current component and an exciting current component by coordinate conversion, wherein the magnetic flux value and the torque are controlled so that the load angle δ is equal to or less than a predetermined value. A control device for a synchronous motor, wherein the exciting current is controlled according to a value calculated from a current value. 2. A synchronous motor control device which converts a current of a synchronous motor into a d-axis current component and a q-axis current component of a rotating magnetic pole coordinate axis (d, q axes) by coordinate conversion and controls the load angle δ. And a d-axis current and a q-axis current that are corrected and controlled in accordance with a value calculated from a magnetic flux value and a torque current value such that is equal to or less than a predetermined value. 3. A synchronous motor control device for converting a current of a synchronous motor into a torque current component and an excitation current component by coordinate conversion and controlling the same, wherein the set value is set so that the load angle δ is equal to or less than a predetermined value. A control device for a synchronous motor, wherein an exciting current is controlled in accordance with a deviation between the control current and the δ detection value. 4. A synchronous motor control device which converts a current of a synchronous motor into a d-axis current component and a q-axis current component of rotating magnetic pole coordinate axes (d, q axes) by coordinate conversion and controls the load angle δ. And a d-axis current and a q-axis current are corrected and controlled in accordance with a deviation between the set value and the detected δ value so that the value is equal to or less than a predetermined value.