JP2856564B2 - Control device for synchronous motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 [Object of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for driving a synchronous motor with a variable voltage and variable frequency power supply 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 a separately excited commutation and a driving method using vector control. Among them, vector control is capable of high-performance driving and is applied to fields that require fast response and precise control. FIG. 4 shows an example of a conventional vector control method.

FIG. 4 shows an example in which the speed of a synchronous motor is controlled using an automatic field weakening method. The field winding 21 of the synchronous motor 2 is DC-excited by a power converter 4 for the field. Drive power is supplied from the power converter 1. The speed control unit 40 sets the speed reference ω ^* And the speed detection signal ω of the synchronous motor 2 to compare the torque reference T ^* Is output. The speed detection signal ω is obtained by differentiating the signal θ of the position detector 3 for detecting the rotation angle of the synchronous motor 2 with the differentiator 41. The function unit 42 outputs the speed detection signal ω
According to the magnetic flux reference φ ^* To enable automatic field weakening, and the function unit 43 outputs φ ^* from the characteristics of the synchronous motor ^. Field current reference I _f ^{* according to} Is output. Also, the divider 44 is T ^* Is φ
^* And the current reference i _T ^* Is output.

The armature current and the field current of the synchronous motor 2 are
It is detected by the flow detectors 11 and 12. On the other hand, the position detector 3 and the position
The position calculator 5 calculates the position of the rotor magnetic pole of the synchronous motor.
You. The three-phase armature current detected by the current detector 11 is a dq axis
In the current calculator 13, d is added together with the position signal from the position calculator 5.
Current detection value i on q axis_d, I_qIs calculated as This
And the field current detection value i_fFrom the magnetic flux calculator 6
The armature magnetic flux is calculated. In the magnetic flux calculator 6, the detected current and
D-axis magnetic flux φ parallel to the rotor magnetic pole from the magnetic pole position_dAnd this
Q-axis magnetic flux φ orthogonal to_qAnd the angle δ of the resultant magnetic flux vector
Is calculated. In the current reference calculator 7, the torque current command i_T
^* Armature current reference value perpendicular to magnetic flux direction from angle and angle δ
i_d ^* , I_q ^* Is calculated. The magnetic flux calculator 6 is shown in FIG.
From the voltage equation of the synchronous motor expressed on the dq axis
Departure, block diagram of the formula to calculate the magnetic flux on the dq axis
It is represented by d-axis magnetic flux φ_dAnd q-axis magnetic flux φ_qIs next
It is shown by the formula. φ_d= L_ad(1 + T_d2S) / (1 + T_d1S) × (i_d+ I_f) +1_a× (i_d+ I_f) (1) φ_q= L_aq(1 + T_q2S) / (1 + T_q1S) × i_q+1_a× i_q  (2)

[0005] where S is a Laplace operator, _Lad, L _aq mutual inductance dq axes, _{1 a} time constant related to the armature leakage _{inductance, T a1, T} a1 damper resistor and synchronous inductance of each dq axes , T _d2 and T _q2 are time constants relating to the damper resistance and the leakage inductance of the dq axes, respectively. d-axis magnetic flux phi _d is computed from the sum of the field current i _f and d-axis armature current i _d, q-axis magnetic flux phi _q is calculated from the q-axis current i _q. δ is the angle of the magnetic flux with respect to the d-axis direction, and is calculated as follows: δ = tan −1 (Φ _q / Φ _d ) (3) Current reference calculator 7 of Figure 4, torque current reference i _T ^* And from the angle [delta], the dq-axis current reference i _d ^* ,
i _q ^* Is calculated by the following equation. _id ^* = −i _T ^* ・ Sin δ (4) i _q ^* = I _T ^* ・ Cosδ (5)

[0006] That is, the torque component current is calculated by calculating the calculated magnetic flux.
Command to go straight. Calculated current reference value is detected
The voltage reference value v on the dq axis is compared with the
_d ^* , V_q ^* Is output as Amplifier 9 is usually a proportional product
It is composed of a divider. This voltage reference value is calculated by the position calculator 5
And three-phase winding voltage command v_u ^* , V_v ^* , V
_w ^* Get. This value is an alternating current that varies with the rotational electrical angular frequency.
And is added to the synchronous motor 2 via the power converter 1.
It is.

[0007] On the other hand the field current i _f of the synchronous motor reference value i
_f ^* And the field voltage reference v _f ^* And is controlled via the field power converter 4.

As described above, the magnetic flux on the dq axes is calculated from the armature current and the field current, and the current corresponding to the torque of the armature is caused to flow in a direction perpendicular to the calculated magnetic flux, thereby obtaining the same armature current. But high torque can be obtained. The vector control method is described in K. Power E by Bose
It is also described in electronics and AC Drives.

[0009]

In the speed control in the weak field range, the speed is controlled by the field current while keeping the armature voltage constant. The current becomes very small. For example, when the field weakening range is 1: 5, the field current is 1/5 or less of the rated current. When a large load change occurs in such a region, the armature current changes greatly, and the armature reaction has a large effect on the field current. In this case, as shown in FIG. 6, when the armature reaction occurs in the direction in which the field current _if decreases, a phenomenon occurs in which the motor speed becomes unstable.

In general, the field circuit is configured to flow a current in one direction. Therefore, the above-described armature reaction becomes large, and if the field current is suppressed to zero or less, the field current becomes a negative current. , The field control becomes impossible. For this reason, the magnetic flux cannot be established as standard, and a predetermined torque cannot be output for a sudden load change. Therefore, stable control cannot be performed at a high speed with a wide field range.

When the energy is large, the field current does not flow to the negative side and is accumulated, resulting in a field overvoltage, which may destroy the semiconductor element of the field circuit.
Therefore, it cannot be applied to a high-speed system with a wide field weakening range.

The present invention has been made in order to improve the above-mentioned drawbacks. The present invention has been made in view of the above problem. It is an object of the present invention to provide a synchronous motor control device with high performance. [Configuration of the Invention]

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a control power supply for supplying power of a variable voltage and a variable frequency to a synchronous motor, and a variable field winding on a field winding of the synchronous motor. An excitation power supply for supplying a current ( _if ), and dq-axis current components in the same direction (d-axis) and the orthogonal direction (q-axis) as the rotor magnetic poles from the armature current of the synchronous motor and the position of the rotor. (i _d, i _q) and the current calculation unit to obtain a magnetic flux calculating unit for simulating the magnetic flux of the synchronous motor the dq-axis current component (i _d, i _q) from the interfacial current (i _f), the speed A speed control unit that obtains a current command by comparing a command and a detection speed of the synchronous motor;
Said current command and the dq-axis current command from the output of the magnetic flux calculation unit (i _d ^* , I _q ^* ) And the current command calculation portion for obtaining a voltage command calculation portion for obtaining a voltage command for the control power supply unit in accordance with the deviation of the dq axis current command and the dq-axis current component (i _d, i _q), the rate said detectable Field current command ( _if ^*) for the excitation power supply unit in accordance with ) Comprises a field current command unit to obtain an apparatus for controlling a speed by an automatic field weakening, the interfacial current command (i _f ^* ) Is partially or entirely increased with respect to the field current command ( _if2 ^* ) Is provided, and the field current command ( _if2 ^* ) Is set as the actual field current command.

[0014]

The compensation means limits the minimum field current to a predetermined value so that the field current does not become zero even when an armature reaction occurs.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, a field current compensator 30 is newly provided.
Other elements are the same as those shown in FIG.
It is. The field current compensator 30 outputs the field current command i_f ^* Compensate
And the actual field current command i_f2 ^* Get the compensation
2 is shown in FIG. This compensation characteristic C₁, C_TwoIs the field current
Field current reference i which is the input of compensator 30_f ^* On the horizontal axis
Output i_f2 ^* Indicates a function with the vertical axis. Compensation
Sex C₁in the case of

Field current reference _if ^* If is the minimum field current limit value i _fMIN smaller than, i _f2 ^* To the value of ifMIN. _if ^* But i _fMIN case greater than i _f2 ^* = _If ^* Determine the function so that

This minimum field current limit value _ifMIN is _caused by armature reaction even when a large load is applied in the weak field region.
The field current is set so as not to be less than zero.

As described above, the field current i _f ^* Increased field current i _f the minimum field current limit value i _fMIN in region is small
Is input to the magnetic flux calculator 6, the internal phase difference angle δ is calculated by the block diagram of FIG. 5, the d-axis magnetic flux φ _d is increased by the increase of the field current, and the internal phase difference angle is opened. The d-axis current _id ^* via the reference calculator 7 Is increased.

This _id ^* The increase of the field current i _f ^* Is offset by the magnetic flux due to the increase in the magnetic flux, so that control can be performed without increasing the magnetic flux. As a result, the output voltage is kept constant, so that the voltage does not become excessive.

By appropriately setting the minimum field current limit value _ifMIN , the field current does not become zero due to the armature reaction even in a high-speed region where the field weakening range is wide, so that the field control can be performed stably. Therefore, stable control characteristics can be realized even with a large load change. This is shown in FIG. The solid line indicates the characteristic according to the present embodiment, and the dotted line indicates the conventional characteristic. Further, the field current as the compensation characteristic C ₂ i _f ^* On the other hand, the same effect can be obtained only by biasing the minimum field current _ifMIN .

[0022]

According to the present invention, there is provided a synchronous motor control capable of performing stable speed control without causing control failure or torque shortage even when a sudden load change occurs in high-speed operation with a wide field weakening range. A device is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a compensation characteristic diagram of the embodiment.

FIG. 3 is a characteristic diagram for explaining the effect of the embodiment.

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

FIG. 5 is a block diagram of a magnetic flux calculator.

FIG. 6 is a characteristic diagram for explaining a problem of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Power converter 2 ... Synchronous motor 3 ... Position detector 4 ... Field power converter 5 ... Position calculator 6 ... Magnetic flux calculator 7 ... Current reference calculator 9, 10 ... Amplifier 11, 12 ... Current detector 13 dq-axis current calculator 14 coordinate converter 21 field winding 30 field current compensator 40 speed controller 41 differentiator 42, 43 function unit 44 divider

Claims (1)

(57) [Claims] A control power supply for supplying electric power of a variable voltage and a variable frequency to a synchronous motor; an excitation power supply for supplying a variable field current ( _if ) to a field winding of the synchronous motor; a current calculating unit for obtaining from the armature current and position of the rotor of the motor dq-axis current component (i _d, i _q) of the magnetic pole in the same direction of the rotor (d-axis) and the perpendicular direction (q-axis), and the dq-axis current component (i _d, i _q) and flux calculating unit for simulating the magnetic flux of the synchronous motor from the interfacial current (i _f), a current command by comparing the detected speed of the speed command and the synchronous motor a speed control unit to obtain, dq axis current command from the output of the current command and the magnetic flux calculation unit (i _d ^* , I _q ^* ), And the dq
Axis current command and the dq-axis current component (i _d, i _q) a voltage command calculation portion for obtaining a voltage command for the control power supply unit in accordance with the deviation of the field current with respect to the excitation power supply unit in accordance with the detection speed Command ( _if ^* ) Comprises a field current command unit to obtain an apparatus for controlling a speed by an automatic field weakening, the interfacial current command (i _f ^* ) Is partially or entirely increased with respect to the field current command ( _if2 ^* ) Is provided, and the field current command ( _if2 ^* ) Is an actual field current command.