JPH06165561A - Controller for synchronous motor - Google Patents

Abstract

PURPOSE:To correct positional shift of rotor being detected automatically when vector control is carried out by detecting rotor position of a synchronous motor. CONSTITUTION:The controller for synchronous motor comprises means 22 for detecting d-axis voltage of a synchronous motor 2, and a position operating means 5 for detecting no-load state from the current of the synchronous motor and outputting a position signal representative of rotor position corrected by d-axis voltage under no-load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor controller for driving a synchronous motor with a variable voltage and variable frequency power source such as a cycloconverter or an inverter.

[0002]

2. Description of the Related Art As a method of driving a synchronous motor with a variable voltage and a variable frequency, there are a non-commutator motor using separately excited commutation and a driving method using vector control. Of these, vector control enables high-performance driving, and is applied to fields that require fast response and precise control. FIG. 4 shows a conventional device of this type. 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, and 4 is field power. A converter, 5 is a position calculator, 7 is 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 synchronous motor 2 is supplied with an armature current and a field current.
It is detected by the flow detectors 11 and 12. On the other hand, position detector 3 and position
The calculator 5 calculates the position of the rotor magnetic pole of the synchronous motor.
It The three-phase armature current detected by the current detector 11 is the dq axis
The current calculator 13 outputs the position signal from the position calculator 5 together with the position signal d.
It is calculated as a current detection value on the q-axis. Current reference calculation
Torque command T^* And magnetic flux command Φ^* And motor
Number to current reference value i_d ^* , I_q ^* And field current reference i
_f ^* Is calculated.

The calculated current reference value is compared with the detected value, and the dq-axis voltage reference value v _d ^{* is obtained} 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 and the three-phase winding voltage v _u ^* , V _v ^* , V _w ^* To get 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 a reference value _if ^*
And the detected value are compared, the field voltage reference is obtained by the amplifier 10 according to the deviation, and the field power converter 4 is driven. FIG. 3 is a detailed view of the position calculator 5 shown in FIG.
61 is a position converter and 62 is an adder. The position converter 61 converts a mechanical angle into an electrical angle, that is, calculates the equation (1). Electrical angle = mechanical angle * (p / 2) (1) (where p is the number of motor poles) Furthermore, the offset amount is set so that the position of the field magnetic pole and the 0 position of the output of the position calculator match. to add.

[0006]

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, and it is difficult to mount them 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 position (center point) of the field magnetic pole serves as the reference, and it is convenient to set it as the direction of the field magnetic flux when considering vector control. The position of the magnetic pole and the direction of the field magnetic flux theoretically match.

In this way, the position of the field magnetic pole and the 0 position of the position detector are made to coincide with each other. However, if the two are displaced over the years, for example, the displacement of the coupling portion between the electric motor and the position detector, or , If the misalignment of the rotation stop of the position detector itself occurs, it will have a serious effect. The magnetic flux of the synchronous motor is determined by the equations (2) and (3). The torque is given by the equation (4). _{Φ d = L ad × (i} d + i f) + l a × i d ...... (2) Φ q = L aq × i q + l a × i q ...... (3) T = Φ d × i q -Φ q × i _d ...... (4) If normal synchronous motor, since it is designed so that the maximum torque is obtained at unity power factor, the current i as shown in FIG. 5
And the magnetic flux Φ are orthogonal.

Here, a mechanical deviation of 1 ° corresponds to an electrical deviation of 6 ° in a multi-pole machine such as a 12-pole machine. A vector diagram at this time is shown in FIG. In FIG. 6, the magnetic flux Φ decreases, and the angle between the current i and the magnetic flux Φ is 90 °.
Due to the above opening, the torque is insufficient by about 15%. This becomes a problem in steel plants where rolling is performed by the maximum output of the electric motor.

The present invention has been made to improve the above-mentioned drawbacks, and an object of the present invention is to realize a control device for a synchronous motor which can controllably correct even if a mechanical displacement occurs in a sensor. And

[0010]

In the present invention, a dq-axis voltage detector and a no-load detector are provided, and the offset amount is corrected by the voltage vector when there is no load.

[0011]

The apparent 0 point is different due to the mechanical deviation described in the above problem. The voltage vector when there is no load is in the direction of the main q-axis, but at this time, it shifts from the direction of the q-axis. In the present invention, the mechanical deviation can be compensated by correcting the amount of deviation of the voltage vector under no load from the q-axis by the no-load detector to the offset amount.

[0012]

1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 20 is a voltage detector, 22 is a dq voltage calculator, and the same elements as those shown in FIG. 2 is a detailed diagram of the position calculator 5 shown in FIG. 1, where 64 is an amplifier, 65 is a comparator, and 66.
Is a switch.

The comparator 65 compares the current i of the electric motor with a certain set level and determines that there is no load when the current value is small. The switch 66 closes the contact when it is determined by the output of the comparator 65 that there is no load. The three-phase armature voltage detected by the voltage detector 20 is calculated by the dq axis voltage calculator 22 as a voltage detection value on the dq axes together with the position signal from the position calculator 5. At no load, v _d becomes 0. The amplifier 64 is composed of a proportional-plus-integral amplifier, which compares v _d with 0 when there is no load and outputs an offset correction amount so that v _d becomes 0. As a result, even if a mechanical shift occurs, it is detected that the voltage vector at the time of no load is shifted, and the offset amount is corrected so that it becomes 0. Therefore, problems such as insufficient torque are eliminated.

According to the above description, in this embodiment, even if a mechanical deviation occurs and the field magnetic pole position and the output of the position calculator differ, the deviation is detected and corrected by the voltage vector. There is no problem and the desired motor characteristics can be output.

[0015]

As described above, according to the present invention, even if a mechanical deviation occurs and the field magnetic pole position and the output of the position calculator differ, the deviation is detected and corrected by the voltage vector, so that the maximum output is obtained. It is possible to provide a control device for a synchronous motor that can be applied to severe applications such as rolling by rolling.

[Brief description of drawings]

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

FIG. 2 is a detailed view of the position calculator 5 of the above embodiment.

FIG. 3 is a detailed diagram of a position calculator of a conventional device.

FIG. 4 is a configuration diagram of main parts of a conventional device.

FIG. 5 is a vector diagram when the vector i _d matches the magnetic pole.

FIG. 6 is a vector diagram when the vector i _d deviates from the magnetic pole.

[Explanation of symbols]

 1 ... Power converter 2 ... Synchronous motor 3 ... Position detector 4 ... Field power converter 5 ... Position calculator 6 ... Flux calculator 7 ... Current reference calculator 9, 10 ... Amplifier 11, 12 ... Current detector 13 ... dq-axis current calculator 14 ... coordinate converter 20 ... voltage detector 22 ... dq-axis voltage calculator

Claims (1)

[Claims] 1. A drive device of a synchronous motor for driving a three-phase synchronous motor by a power converter that supplies electric power of variable voltage and variable frequency, a current detector for detecting an armature current of the synchronous motor, and the synchronous motor. A position detector for detecting the rotor position of the rotor, and a component of the current from the current detector in the direction (q axis) orthogonal to the same direction (d axis) as the magnetic pole of the rotor is calculated by the signal from the position detector. Current calculator for detecting field current, current command calculator for calculating dq axis current command and field current command from magnetic flux command and torque command, dq axis current command and current calculation Voltage reference calculator for calculating the voltage reference on the dq axes according to the deviation from the current of the power supply, and a coordinate converter for converting the dq axis voltage reference to the three-phase voltage reference of the power converter, Electric motor voltage And a direction (q) perpendicular to the same direction (d-axis) as the magnetic pole of the rotor by the voltage detected by the voltage detector and the signal from the voltage detector and the signal from the position detector.
Axis) and a voltage calculator for detecting a no-load state of the synchronous motor, and an offset amount for aligning the zero point of the rotor and the zero point of the position detector is determined by a voltage vector at no load. A control device for a synchronous motor, which is provided with a correcting means.