JPH10286000A - Controller for synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue stable control even at the time of overload operation close to a maximum internal phase angle. SOLUTION: When an internal phase angle δ is increased by heavy-load operation in the synchronous motor and a functional value f(δ) exceeds a fixed value (a), a correction command S is outputted from a stability-limit decision section 37, and a torque-reference correction section 38 corrects a torque reference T* so as to inhibit the torque reference T* when the correction signal S is outputted. The internal phase angle δ rapidly reaches a maximum internal phase angle by the correction operation and is not limited by an internal phase angle limiting section 13, and stable operation can be continued without generating control instability.

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 for controlling a synchronous motor using vector control.

[0002]

2. Description of the Related Art As a system for driving a synchronous motor using a variable voltage variable frequency power source such as a cycloconverter or an inverter, there are a non-commutator motor using a separately excited commutation and a driving system using vector control. Among them, the vector control is applicable to rolling control of a steel plant which requires high-performance driving and requires fast control response and precise control. FIG. 7 shows an example of this type of conventional apparatus.

FIG. 7 shows an example in which the speed of a synchronous motor is controlled. 1 is a three-phase synchronous motor, 2 is a field winding thereof, and a power conversion unit 3 is an electric motor of the synchronous motor 1. A three-phase variable frequency AC (drive) current is supplied to the motor, and the power converter 4 supplies a DC (excitation) current to the field winding 2 of the synchronous motor. The three-phase to two-phase converter 5a converts the three-phase armature current detected by the current detector 5 on the dq (orthogonal rotation coordinate) axis based on the rotor magnetic pole position detected by the position detector 7. 2
It is converted into the current detection values Id and Iq of the phase. Speed converter 7a
Is the synchronous motor 1 based on the position signal detected by the position detector 7.
Is detected.

The speed controller 8 determines a torque reference T ^* based on the deviation between the speed reference ωr ^* and the rotation speed ωr, and the torque reference T Output ^* . On the other hand, the field-weakening control unit 10 determines the magnetic flux command φ ^* based on the rotation speed ωr, and sets the torque reference T ^* to the magnetic flux command φ ^* by the divider 9a ^.
In dividing and obtains a torque current reference IT ^*, and outputs a maximum torque current reference following range limited torque current reference IT via a torque current reference limiting portion 14 ^*.

[0005] The magnetic flux calculation unit 11 calculates the magnetic fluxes φd and φq on the dq axes based on the armature current detection values Id and Iq on the dq axes, the field current detection value If, and a constant determined by the synchronous motor. The phase difference angle calculator 12 calculates the internal phase difference angle δ from the magnetic fluxes φd and φq based on the equation (1).

[0006]

Δ = tan ⁻¹ (φq / φd) (1) The internal phase difference angle δ is output via the internal phase difference angle limiting unit 13 to be limited to a range equal to or less than the maximum internal phase difference angle. The vector calculation unit 15 calculates two-phase armature current references Id ^* and Iq ^* on the dq axes from the torque current reference IT ^* and the internal phase difference angle δ based on the equations (2) and (3).

[0007]

Id ^* = − IT ^* · sinδ (2) Iq ^* = IT ^* · cosδ (3) The two-phase / three-phase converter 15 a calculates the rotor magnetic pole position detected by the position detector 7. The two-phase armature current reference Id
^* , Iq ^* are replaced with the usual three-phase armature current references Iu ^* , Iv ^*
, Iw ^* to control the power conversion unit 3. As a result, three-phase alternating currents corresponding to Iu ^* , Iv ^* , and Iw ^* are supplied at a power factor of 1 from the power conversion unit 3, and the synchronous motor 1 is controlled to a speed corresponding to the speed reference ωr ^* .

The field current control unit 16 controls the field current reference If ^* based on the armature current detection value Id on the d-axis, the magnetic flux command φ ^*, and a constant determined by the synchronous motor to obtain a power factor of 1 ^.
To control the power conversion unit 4 to control the exciting current If supplied to the field winding 2 to a value corresponding to the field current reference If ^* .

[0009]

However, in the above-mentioned conventional apparatus, since the internal phase difference angle δ and the torque reference T ^* are independently limited, there is a problem that the control becomes unstable depending on the operation state. Hereinafter, this phenomenon will be described in detail.

FIG. 8 is a vector diagram showing a case where an AC current is supplied to the synchronous motor at a power factor of 1 as described above. The dq-axis components of the armature current I are represented by Id, Iq, and the armature voltage V. Where Vd and Vq are the dq-axis components, Xd and Xq are the dq-axis components of the synchronous reactance X, and δ is the internal phase difference angle,
The relations of equations (3) and (4) hold.

[0011]

Vd = Vsinδ = Iq · Xq = I · Xq · cosδ (3) I = (V / Xq) · tanδ (4) At this time, the power factor is controlled to 1 and the generated torque T is changed to the armature current. Considering that it is proportional to I, the following relationship exists between the internal phase difference angle δ and the torque T.

[0012]

T = K · tan δ (5) (where K is a proportional constant determined by the synchronous motor) Further, the change of the torque T with respect to the change of δ is also important for control. This is because a slight change in the internal phase difference angle δ greatly affects the generated torque in the heavy load operation region. The change amount of tan δ with respect to the change amount of δ is (6)
It is obtained by the equation and can be shown as in FIG.

[0013]

Dtanδ / dδ = 1 / (cosδ) ² (6) As is apparent from FIG. 9, as δ approaches 90 °, the value of tanδ rises sharply and becomes unstable in control. In the conventional apparatus, in order to prevent this, the value of δ is limited by the internal phase difference angle limiting unit 13 so as not to exceed a predetermined value (for example, 85 °).

However, since the relationship between the internal phase difference angle δ and the torque T is deep and the internal phase difference angle δ and the torque reference are independently limited, the motor is operated near the limit value of the internal phase difference angle δ during overload. In such a case, when a slight increase in the torque occurs, the internal phase difference angle δ is limited, and the control may suddenly become unstable. This phenomenon becomes a problem in steel plants and the like that continue rolling in an overloaded state.

The present invention has been made in order to solve the above-mentioned problem. The present invention relates to the limitation of the internal phase difference angle and the limitation of the torque reference, and the internal phase difference angle is operated near the limit value during overload. Even in such a case, an object of the present invention is to provide a control device for a synchronous motor that can perform an appropriate torque limit and continue stable control.

[0016]

In order to achieve the above object, a synchronous motor control device according to the present invention comprises: a power converter for supplying an alternating current to drive a synchronous motor based on a dq-axis current reference; And a torque current reference from the torque reference and a d detected from the armature current of the synchronous motor.
From the q-axis current and the detected field current of the synchronous motor, dq
Axis magnetic flux, an internal phase difference angle is obtained from the dq axis magnetic flux,
A vector control unit that obtains the dq-axis current reference from the internal phase difference angle and the torque current reference; a stability limit determination unit that outputs a correction command based on the internal phase difference angle; And a torque reference correction unit that corrects the torque reference when the internal phase difference angle exceeds a predetermined value. (Claims 1 to 6) A speed controller for outputting the torque reference from a speed reference and a detected speed value of the synchronous motor controls the speed of the synchronous motor. (Claim 7)

[0017]

FIG. 1 shows an embodiment (basic form) according to the first aspect of the present invention, in which a main part structure related to a torque reference T ^* related to vector control and an internal phase difference angle δ is shown. Is shown. In FIG. 1, reference numeral 37 denotes a stability limit determination unit that outputs a correction command S when a function value (including f (δ) = δ) calculated based on the internal phase difference angle δ exceeds a predetermined value as a determination condition. Is a torque reference correction unit that outputs a torque reference T ^{* ′} corrected so as to suppress the torque reference T ^* when the correction command S is output. The other components are the same as those of the related art (FIG. 7), and are denoted by the same reference numerals.

The internal phase difference angle .delta.
2, the torque reference T ^* is supplied from the speed control unit 8, the torque reference T ^{* '} corrected by the torque reference correction unit 38 is supplied to the divider 9a, and is divided by the magnetic flux command φ ^* to obtain the torque current T ^*. is converted to the reference iT ^*, internal phase angle [delta] 'is supplied to the vector operation unit 15 output from the torque current reference iT ^* and internal phase angle limiter 13.

In the above configuration, in the case of a low-load operation in which the value of the internal phase difference angle δ does not satisfy the determination condition of the stability limit determination section 37, the correction command S is not output, the torque reference correction section 38 is bypassed, and the torque reference The torque reference T ^* output from the limiting unit 9 is used for vector control as it is. Therefore, in this case, the system is limited on the basis of the maximum torque, which is the limit of system protection as in the related art.

As the load increases, the torque reference T ^* increases, and as the torque reference T ^* increases, the internal phase difference angle δ also increases, and the function value f (δ) calculated based on the internal phase difference angle δ becomes When the limit value a of the determination condition is exceeded, a correction command S is output from the stability limit determination unit 37, the torque reference correction unit 38 starts operating, and a function (limit) is applied to the torque reference T ^* .
(T ^* )) and the corrected torque reference T ^{* '}
Is output.

By performing the vector control shown in FIG. 7 using the torque reference T ^{* '} corrected in this manner, the value of the internal phase difference angle δ becomes close to the maximum internal phase difference angle set in the internal phase difference angle limiting unit 13. Even when the engine is operated under heavy load and the torque reference T ^* increases, appropriate suppression can be applied to the torque reference, so that the internal phase difference angle δ is not suddenly limited and the operation is continued at the maximum output state. The operation can be continued without unstable control even in severe applications.

The dynamic characteristics of synchronous motor control can be improved by determining the stability limit of the synchronous motor using the function value (f (δ)) calculated based on the internal phase difference angle δ. 2 to 6 specifically show the contents of the above embodiment.

FIG. 2 shows an embodiment according to a second aspect of the present invention. Reference numeral 37a denotes a correction command when the value of tan δ calculated based on the internal phase difference angle δ exceeds a predetermined value A as a judgment condition. S1 is output (first) stability limit determination section, 32
Is 1 / (cos δ) calculated based on the internal phase difference angle δ
² values and outputs the correction instruction S2 when exceeding a predetermined value B to determine the condition (second) stability limit determination section, 38a when the correction command S1 is outputted, to restrict the torque reference T ^* to a predetermined value ^'torque reference limit unit for outputting, 38b when the correction instruction S2 is output, the torque reference T ^* corrected to limit the torque reference T ^* rate of ^change' torque reference T ^* corrected to output This is a torque reference change rate limiting unit. The limit value set in the torque reference limiting unit 38a is set based on the torque reference at the stability limit.

In the above configuration, in the case of a low load operation in which the internal phase difference angle δ does not satisfy both the determination conditions of the stability limit determination units 37a and 37b, neither of the correction signals S1 and S2 is output, and the torque reference limit unit is not output. 38a and the torque-based change rate limiting unit 38b are bypassed, and the torque-based limiting unit 9
Torque reference output from the T ^* is used as such in the vector control. Therefore, in this case, the system is limited on the basis of the maximum torque, which is the limit of system protection as in the related art.

As the load increases, the torque reference T ^* and the internal phase difference angle δ increase, and 1 is calculated based on the internal phase difference angle δ.
When / (cos δ) ² exceeds the limit value B set in the stability limit determining section 37b, a correction command S2 is output, the torque reference change rate limiting section 38b starts operating, and the torque reference T ^*
The amount of increase (change amount) during a certain period of time is limited. As a result, a steep increase in the torque reference in this state is suppressed.

As the torque reference further increases, the internal phase difference angle δ increases, and ta calculated based on the internal phase difference angle δ
When nδ exceeds the limit value A set in the stability limit determining unit 37a, the torque reference limiting unit 38a operates. In response, the torque reference is limited to a predetermined value. According to this embodiment, three stages of torque limitation can be performed in view of control stability.

FIG. 3 shows an embodiment according to claim 3 of the present invention. The stability limit judging section 37 obtains tan δ based on the internal phase difference angle δ, and when the tan δ exceeds a predetermined value A, a correction command is issued. In response to the correction command S, the torque reference correction section 38 operates to limit the value of the torque reference T ^* to a predetermined value. According to the present embodiment, the torque reference can be limited before the unstable torque reference is obtained by a simple configuration.

FIG. 4 shows an embodiment according to claim 4 of the present invention. The stability limit judging section 37 obtains tan δ based on the internal phase difference angle δ, and when tan δ exceeds a predetermined value A, a correction command is issued. S is output, and the torque reference correction unit 38 operates in response to the correction command S to limit the amount of increase (change) of the torque reference T ^* during a certain time. According to the present embodiment, it is possible to suppress the rising speed of the torque reference before the unstable torque reference is achieved with a simple configuration, and to perform stable torque control.

FIG. 5 shows an embodiment according to claim 5 of the present invention, wherein the stability limit judging section 37 obtains 1 / (cos δ) ² based on the internal phase difference angle δ, and 1 / (cos δ) ² Outputs a correction command S when the value exceeds a predetermined value B.
In response, the torque reference correction unit 38 operates to operate the torque reference T ^*.
The amount of increase (change amount) during a certain period of time is limited. According to the present embodiment, it is possible to suppress the rising speed of the torque reference before the unstable torque reference is achieved with a simple configuration, and to perform stable torque control.

FIG. 6 shows an embodiment according to claim 6 of the present invention. The stability limit judging section 37 obtains 1 / (cos δ) ² based on the internal phase difference angle δ, and 1 / (cos δ) ² Outputs a correction command S when the value exceeds a predetermined value B.
In response, the torque reference correction unit 38 operates to operate the torque reference T ^*.
Is limited to a predetermined value. According to the present embodiment, the torque reference can be limited before the unstable torque reference is obtained by a simple configuration.

Further, according to these embodiments, even when the synchronous motor is operated under heavy load by speed control, the internal phase difference angle is not sharply limited, and stable speed control can be continued. .

[0032]

According to the control apparatus for a synchronous motor of the present invention, it is possible to perform correction so as to suppress the torque reference before reaching the maximum internal phase difference angle at which the synchronous motor control becomes unstable. During operation, the internal phase difference angle is not suddenly limited, and stable operation can be performed even in a severe case where operation is continued at the maximum output state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of an embodiment according to claim 1 of the present invention.

FIG. 2 is a configuration diagram of a main part of an embodiment according to claim 2 of the present invention.

FIG. 3 is a configuration diagram of a main part of an embodiment according to claim 3 of the present invention.

FIG. 4 is a configuration diagram of a main part of an embodiment according to claim 4 of the present invention.

FIG. 5 is a configuration diagram of a main part of an embodiment according to claim 5 of the present invention.

FIG. 6 is a configuration diagram of a main part of an embodiment according to claim 6 of the present invention.

FIG. 7 is a configuration diagram of a synchronous motor speed control device to which the present invention is applied.

FIG. 8 is a vector diagram for explaining vector control used in the control device.

FIG. 9 is a characteristic diagram illustrating a relationship between an internal phase difference angle δ and tan δ for explaining a problem of the control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Synchronous motor (armature) 2 ... Field winding 3 ... Power conversion part (for armature) 4 ... Power conversion part (for field) 5 ... Current detector (for armature) 5a ... 3 phase 2 phase Converter 6: Current detector (for field) 7: Position detector 7a: Speed converter 8: Speed controller 9: Torque reference limiter 9a: Divider 10: Field weakening controller 11: Magnetic flux calculator 12: Internal Phase difference angle calculation unit 13 internal phase difference angle restriction unit 14 torque current reference restriction unit 15 vector calculation unit 15a two-phase three-phase conversion unit 16 field magnetic current control units 37, 37a, 37b stable stability determination unit 38 38a, 38b: torque reference correction unit

Claims (7)

[Claims] 1. A power converter for supplying an alternating current to drive a synchronous motor based on a dq-axis current reference, a torque current reference being obtained from a magnetic flux reference and a torque reference, and being detected from an armature current of the synchronous motor. Dq-axis magnetic flux is obtained from the dq-axis current and the field current detection value of the synchronous motor, an internal phase difference angle is obtained from the dq-axis magnetic flux, and the dq-axis current reference is obtained from the internal phase difference angle and the torque current reference. A vector control unit, a stability limit determining unit that outputs a correction command based on the internal phase difference angle, and a torque reference correction unit that corrects the torque reference based on the correction command, wherein the internal phase difference angle is a predetermined value. A control device for a synchronous motor, wherein a correction is made so as to suppress the torque reference when the torque exceeds the threshold. 2. The control apparatus for a synchronous motor according to claim 1, wherein said stability limit determining section obtains 1 / (cos δ) ² based on said internal phase difference angle δ, and when said value exceeds a predetermined value. A first stability limit determining unit that outputs a first correction command; and a second stability limit determining unit that obtains tan δ based on the internal phase difference angle δ and outputs a second correction command when this value exceeds a predetermined value. The torque reference correction unit performs correction so as to suppress the rate of change of the torque reference when the first correction command is output, and limits the torque reference to a predetermined value when the second correction command is output. A control device for a synchronous motor. 3. The control device for a synchronous motor according to claim 1, wherein the stability limit determination section obtains tan δ based on the internal phase difference angle δ, and outputs the correction command when this value exceeds a predetermined value. A control unit for controlling the synchronous motor, wherein the torque reference correction unit limits the torque reference to a predetermined value when a correction command is output. 4. The control device for a synchronous motor according to claim 1, wherein the stability limit determining section obtains tan δ based on the internal phase difference angle δ, and outputs the correction command when this value exceeds a predetermined value. A control unit for the synchronous motor, wherein the torque reference correction unit performs correction so as to suppress the rate of change of the torque reference when a correction command is output. 5. The control device for a synchronous motor according to claim 1, wherein the stability limit determination unit obtains 1 / (cos δ) ² based on the internal phase difference angle δ, and when this value exceeds a predetermined value. A control device for a synchronous motor, wherein a correction command is output, and the torque reference correction unit performs correction so as to suppress a rate of change of the torque reference when the correction command is output. 6. The control device for a synchronous motor according to claim 1, wherein said stability limit determination unit obtains 1 / (cos δ) ² based on said internal phase difference angle δ, and when said value exceeds a predetermined value. A control device for a synchronous motor, wherein a correction command is output, and the torque reference correction unit limits the torque reference to a predetermined value when the correction command is output. 7. The synchronous motor control device according to claim 1, further comprising a speed control unit that outputs the torque reference from a speed reference and a detected speed value of the synchronous motor, and controls the speed of the synchronous motor. A control device for a synchronous motor.