JPH06165560A - Controller for synchronous motor - Google Patents

Abstract

PURPOSE:To allow provision of characteristics for forward and reverse rotations by adding a predetermined offset amount to the electric angle depending on the rotational direction of synchronous motor. CONSTITUTION:A switch 64 is switched depending on forward or reverse rotation of a synchronous motor 2 and offset amount of a setter 63 is added to the output thetae' from a position displacement unit 61 in case of forward rotation whereas an offset amount of a setter 63R is added to the output thetae' in case of reverse rotation and outputted as an electric angle thetae. Consequently, when setting is made previously such that the shift between d-axis(same direction as the pole of rotor in the motor 2) and field flux is nullified during forward and reverse rotations, shift between d-axis and field flux can be eliminated for both forward and reverse rotations. This constitution provides characteristics for forward and reverse rotations without causing deficient torque or overvoltage for both rotational directions.

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, and more particularly to a control device for a synchronous motor which detects the position of a magnetic field pole from the angle of a rotating shaft and performs vector control.

[0002]

2. Description of the Related Art There is a system in which a synchronous motor is vector-controlled by a variable voltage, variable frequency power converter to drive it.

FIG. 4 shows the structure of the main part of a conventional device of this type. In FIG. 4, 1 is a power converter, 2 is a three-phase synchronous motor, 21 is a field winding of a synchronous motor, 3 is a position detector, 4 is a field power converter, 5 is a position calculator, and 7 is a position calculator. A current reference calculator, 9 and 10 are amplifiers, 14 is a coordinate converter, 11 and 12 are current detectors, and 13 is a dq axis current calculator.

The current detectors 11 and 12 detect the armature current and the field current of the synchronous motor 2. On the other hand, the position detector 3 and the position calculator 5 calculate the position of the rotor magnetic pole of the synchronous motor. The three-phase armature current detected by the current detector 11 is d along with the position signal from the position calculator 5 by the dq axis current calculator 13.
It is calculated as current detection values i _d and i _q on the q-axis. In the current reference calculator 7, the torque command T ^* And magnetic flux command Φ ^* And the current reference value i _d ^* from the motor constant , I _q ^* And field current reference _if ^* Is calculated.

Current reference value i _d ^* , I _q ^* Is the detected value i _d ,
i _q , respectively, and the voltage reference value v _d ^{* on the} dq axis is compared by the amplifier 9 ^. , V _q ^* Is output as. The amplifier 9 is usually composed of a proportional integrator. This voltage reference value is combined with the output of the position calculator 5 to produce the three-phase winding voltage v _u ^* by the coordinate converter 14 ^. , V _v ^* , V _w ^* Is converted to. This value is the amount of alternating current that changes with the rotating electrical angular frequency. On the other hand, the field current of the synchronous motor is the reference value _if ^* Is controlled by the amplifier 10 and the field power converter 4 so that the deviation is reduced.

The position calculator 5 is, as shown in FIG.
It is composed of a position converter 61 for converting the mechanical angle θ _m into an electrical angle θ _e ′ and an adder 62 for adding the offset amount of the setter 63, and performs the calculation of the equation (1). Electrical angle = mechanical angle × (p / 2) + offset amount (1) (where p is the number of motor poles) Note that the offset amount is the position of the field magnetic pole and the position calculator 5.
The output (electrical angle) is determined so that the 0 position matches.

[0007]

Generally, the position of the magnetic field poles of the rotor and the zero of the position detector attached to the rotor.
The positions do not match perfectly, and it is difficult to attach them accurately so that they match. Therefore, the operation of adding the offset amount as described above is performed on the detection signal side. At this time, the reference is originally the position (center point) of the field magnetic pole, but when considering vector control, it is convenient to set it as the direction of the field magnetic flux. The position of the magnetic pole and the direction of the field magnetic flux theoretically match. However, in reality, as shown in FIG. It is considered that this is caused by the mechanical accuracy of each pole and the imbalance of the winding in the multipole machine. Since such deviation differs depending on the rotation direction, the characteristics of the electric motor differ between forward rotation and reverse rotation. Magnetic flux Φ is determined by equations (2) and (3)
_It is the vector sum of _d and Φ _q . _{Φ d = L ad × (i} d + i f) + l a × i d ... (2) Φ q = L aq × i q + l a × i q ... (3) ( where _{Φ f = L ad × i f} )

However, the actual field flux Φ _{f with} respect to the d-axis
When the deviation is caused by the error angle θ, the actual magnetic flux Φ ′ becomes large at the time of forward rotation and becomes small at the time of reverse rotation as shown in FIG. Therefore, the motor output also has different characteristics in forward and reverse rotation. In a steel plant that performs reversible rolling with the maximum output of an electric motor, such a difference in characteristics becomes a problem.
That is, in the above example, the torque becomes insufficient at the time of reverse rotation, the electric motor voltage becomes excessive at the time of forward rotation, and it becomes impossible to operate at the maximum output.

The present invention has been made to improve the above-mentioned drawbacks, and an object of the present invention is to provide a control device for a synchronous motor capable of correcting the deviation of the field magnetic flux due to forward rotation and reverse rotation and matching the characteristics. And

[0010]

In order to achieve the above object, the present invention provides a synchronous motor drive device for driving a three-phase synchronous motor by a power converter supplying electric power of variable voltage and variable frequency. A current detector that detects an armature current of the synchronous motor, a position calculator that detects an electrical angle from the rotation angle of the synchronous motor, and a current from the current detector in the same direction as the magnetic pole of the rotor by the electrical angle. A current calculator for calculating currents in the (d-axis) component and the orthogonal direction (q-axis) component;
A voltage reference calculator for calculating the voltage on the dq axes according to the deviation between the q-axis current command and the current of the current calculator, and d
A coordinate converter for converting a combined vector of a q-axis voltage reference into a three-phase voltage reference of a power converter, and the position calculator,
Means is provided for adding a predetermined offset amount to the electrical angle according to the rotation direction of the synchronous motor.

[0011]

By the above means, an offset amount for correcting the deviation of the field magnetic poles generated at the time of forward rotation or reverse rotation is added to the electrical angle according to the rotation direction of forward rotation or reverse rotation, and the control characteristics in forward rotation and reverse rotation are made uniform. Will be possible.

[0012]

FIG. 1 shows an embodiment of a control device for a synchronous motor of the present invention. In FIG. 1, (A) is a diagram showing a configuration of a main part, and the same parts as those in FIG.

In FIG. 1A, the forward / reverse rotation discriminator 20 outputs a discrimination signal FR from the signal from the position detector 3 according to the direction of rotation of the synchronous motor 2 (forward rotation or reverse rotation). Position calculator 21 are converts the mechanical rotation angle theta _m of the electric angle theta _e, the electrical angle a value obtained by adding a predetermined offset amount in accordance with the determination signal FR from reverse rotation discriminator 20 theta _e Is provided. Figure 1 (B) shows the position calculator
The internal configuration of 21 is shown, and setters 63F and 63R for respectively setting offset amounts at the time of forward rotation and at the time of reverse rotation, and a switch 64 which is switched by a discrimination signal FR are provided.

With the above configuration, the switch 64 is switched according to whether the synchronous motor 2 is rotating normally or reversely, the offset amount of the setter 63F is set at the time of forward rotation, and the setter 63R is set at the time of reverse rotation.
Is added to the output θ _e ′ of the position converter 61 and output as an electrical angle θ _e . Therefore, if the d-axis and the field magnetic flux Φ _f are set in advance so as to eliminate the deviation between the d-axis and the field magnetic flux Φ _f during the forward rotation and the reverse rotation, it is possible to eliminate the deviation between the d-axis and the field magnetic flux Φ _f during the forward rotation and the reverse rotation. Therefore, it is possible to make the forward rotation and reverse rotation characteristics uniform without causing torque shortage or overvoltage depending on the rotation direction.

[0015]

According to the present invention, even if there is a change in the characteristics due to the deviation of the magnetic flux of the synchronous motor in the forward / reverse rotation, the characteristics of the normal / reverse rotation motor can be matched, so that the reversal can be achieved at the maximum output. It is possible to perform rolling, and it is possible to provide a control device for a synchronous motor having a high operating rate.

[Brief description of drawings]

1A and 1B are diagrams showing an embodiment of the present invention, in which FIG. 1A is a configuration diagram of a main part, and FIG.

FIG. 2 is a diagram showing a relationship between a field magnetic flux of a synchronous motor and a rotor.

FIG. 3 is a vector diagram for explaining a problem caused by deviation of magnetic flux of a synchronous motor.

FIG. 4 is a diagram showing a conventional device, in which (A) is a main part configuration diagram;
(B) is a detailed view of the part.

[Explanation of symbols]

 1 ... Power converter 2 ... Synchronous motor 3 ... Position detector 4 ... Field power converter 7 ... Current reference calculator 9,10 ... Amplifier 11, 12 ... Current detector 13 ... Dq axis current calculator 14 ... Coordinates Converter 20 ... Forward / reverse rotation discriminator 21 ... Position calculator 61 ... Position converter 62 ... Adder 63F, 63R ... Forward / reverse rotation offset amount setter 64 ... Switch

Claims (1)

[Claims] 1. A drive device for a synchronous motor that drives a three-phase synchronous motor by a power converter that supplies electric power of a variable voltage and a variable frequency, and a current detector that detects an armature current of the synchronous motor, and a synchronous motor. The position calculator for detecting the electrical angle from the rotation angle of the rotor and the current from the current detector for the current in the same direction (d-axis) component and the orthogonal direction (q-axis) component as the magnetic pole of the rotor by the electrical angle. Current calculator and dq
Depending on the deviation between the axis current command and the current of the current calculator, d
a voltage reference calculator for calculating the voltage on the q-axis, and this dq
A coordinate converter for converting a composite vector of the shaft voltage reference into a three-phase voltage reference of the power converter, and adding a predetermined offset amount to the electric angle according to the rotation direction of the synchronous motor is added to the position calculator. A control device for a synchronous motor, characterized by comprising means.