JPH04127893A - Controller for synchronous motor - Google Patents

Abstract

PURPOSE:To obtain a high-performance controller for synchronous motor which is stable even in a high driving frequency domain or under a heavy load by finding a reference voltage value on a dq axis by comparing the calculated reference current value on the dq axis with a detected value and transforming the reference voltage value into a three-phase armature winding shaft by means of a coordinate transformer. CONSTITUTION:The three-phase armature current detected by means of a current detector 11 is calculated as a detected current value on a dq axis by means of a dq axis current computing element 13 together with a position signal from a position computing element 5. A magnetic flux computing element 6 calculates an armature magnetic flux from the calculated detected current value and a detected field current value. A command is given so that a torque amount current can intersect the calculated magnetic flux at right angles. A calculated reference current value is compared with the a detected value and outputted as a reference voltage values vd and vq of the dq axis by means of an amplifier 9. The reference voltage values are given to a coordinate transformer 14 and threephase winding voltages vu, vv, and vw are further obtained from the voltage reference values and the output of the position computing element 5. These values become an AC quantity which varies depending upon a rotational electrical angular frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention] (Industrial Application Field) The present invention relates to a control device for a synchronous motor when variable speed control is performed on the synchronous motor using a variable voltage variable frequency power source such as a cycloconverter or an inverter.

(Prior Art) Methods for variable speed control of a synchronous motor using a variable voltage variable frequency power source include a commutatorless motor using separately excited commutation and a drive method using vector control. Among these, vector control allows for high-performance driving and is applied to fields that require fast response and precise control. For example, the vector control method is described in Bose's “Power Electronics
and AC Drives” Prentice-Ha
It is stated in Chapter 8, Section 2.

Figure 5 shows an example of a conventional system, in which 1 is a power converter that is a variable voltage variable frequency power source, and 2 is a three-phase synchronous motor (
(hereinafter simply referred to as 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, 6 is a magnetic flux calculator, 7
is a current calculator, 8 is a coordinate converter, 9゜10 is an amplifier, 1
1.12 is a current detector.

A current detector 11 detects the armature current and field current of the synchronous motor 2.
．． Detected at 12. On the other hand, the position detector 3 and the position calculator 5
Now, calculate the position of the rotor magnetic pole of the synchronous motor. The magnetic flux calculator 6 calculates a d-axis magnetic flux parallel to the rotor magnetic poles and a q-axis magnetic flux perpendicular to the rotor magnetic poles from the detected armature current and the magnetic pole position. The current calculator 7 calculates an armature current reference value 1d+lq (DC amount) parallel and orthogonal to the magnetic flux direction from the torque current command i7 and the magnetic flux calculation value. The coordinate converter 8 obtains a three-phase armature current reference value 1uvv (alternating current amount) from the rotor position signal and the ctq axis current reference value.

The deviation between this reference value and the detected current value is amplified by the amplifier 9 to obtain the armature voltage reference value. 'uy fv, Vy is obtained and the power converter 1 is driven based on this reference.

The field winding 21 of the synchronous motor 2 amplifies the deviation from the field current reference value 17 and the detected value to obtain a field voltage reference, and the field power converter 4 supplies electric power.

(Problems to be Solved by the Invention) In the embodiment shown in FIG. 5, the coordinate converter 8 calculates the reference value (alternating current amount) of the armature current and compares it with the armature current detection value (alternating current amount). The armature voltage is determined according to this value. Since the armature current is an alternating current unless the rotor is stationary, it is necessary to flow a sine wave current corresponding to the drive frequency.

When using a cycloconverter as a power conversion device,
Its output frequency can generally range from zero frequency to near the power supply frequency. In the case of a relatively high output frequency, there is a possibility that a desired alternating current waveform cannot be obtained because the magnitude of the reference value and the actual current differ or the phase changes due to the relationship between the control response of the current control system.

The characteristics of the synchronous motor 2 are greatly influenced by the phase of the current relative to the position of the rotor. Particularly when a heavy load is applied and a large current is flowing, a small change in the current phase can cause a large difference in voltage and power factor, which has a large effect on the characteristics. Furthermore, the current may be distorted and torque pulsation may occur, which may adversely affect the mechanical system.

For this reason, especially in the synchronous motor 2, it is necessary to accurately control the actual current relative to the current reference.

The present invention has been made to improve the above-mentioned drawbacks, and an object of the present invention is to provide a synchronous motor control device that realizes a stable and high-performance device even in a high drive frequency range and heavy load.

[Structure of the invention]

(Means for Solving the Problems) In the present invention, the armature current, the field current, and the magnetic pole position of the rotor are detected, and the magnetic pole direction of the rotor (d-axis) and the direction perpendicular thereto (q-axis) are detected. The armature current reference (DC amount) is determined based on this dq-axis magnetic flux. Compare the current detection value (DC amount) on the dq axis with the current reference, and calculate the dq
Obtain the voltage reference (DC amount) on the axis. This value is converted to the three-phase winding axis of the armature and applied as a voltage reference value (alternating current amount) to drive the power converter.

(Function) Calculate the magnetic flux on the dq axis from the armature current and field current,
High torque can be obtained even with the same armature current by flowing the armature torque current perpendicular to the calculated magnetic flux. By comparison, a voltage reference on the ctq axis is obtained and converted to the three-phase armature winding axis using a coordinate converter.

(Embodiment) FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, 13 is a dq-axis current calculator, 14 is a coordinate converter, and other elements that are the same as those shown in FIG. 5 correspond to the same numbers. FIG. 2 is a configuration example showing a detailed block diagram of the magnetic flux calculation circuit 6 shown in FIG. It is a vessel.

The three-phase armature current detected by the current detector 11 is converted to c along with the position signal from the position calculator 5 by the dq-axis current calculator 13.
It is calculated as a current detection value (DC amount) on the tq axis.

The armature magnetic flux (DC amount) is calculated by the magnetic flux calculator 6 from this value and the field current calibration value. The magnetic flux calculator shown in FIG. 2 is a block diagram representing an arithmetic equation for calculating the magnetic flux along the ciq axis starting from the voltage equation of a synchronous motor expressed on the dq axes. d-axis magnetic flux Φd and q#! Magnetic flux Φ9
is the following formula % formula % Here, S is the Laplace operator, L ad + L aq is the mutual inductance of the d and q axes, 18 is the armature leakage inductance, Td,, T9. are the time constants related to the damper resistance and synchronous inductance of the d and q axes, respectively.

Td2. Tq2 is a time constant related to the damper resistance and damper leakage inductance of the d and q axes, respectively.

The d-axis magnetic flux is calculated from the sum of the field current and the d-axis armature current, and the q-axis magnetic flux is calculated from the q-axis current. δ is the angle of the magnetic flux with respect to the d-axis direction, and is calculated as follows: δ=jan'-+(Φ, , /Φd).

The current calculator 7 in FIG. 1 is a torque current base! ! ! iT
The dq-axis current reference 1d+1q (DC amount) is calculated from the following equation.

ld"-5,7'sin δ j9 = -kodyo + cos δ In other words, the torque current is commanded to run orthogonally to the calculated magnetic flux. The calculated current reference value is compared with the detected value (DC amount), and the amplifier 9 determines the dq-axis voltage reference value y
It is output as d, s, (DC amount). Amplifier 9 is usually constituted by a proportional integrator. This voltage reference value is given to the coordinate converter 14, and is further combined with the output of the position calculator 5 to obtain the three-phase winding voltage fU+ty, Zry. This value becomes an alternating current amount that changes with the rotational electrical angular frequency.

On the other hand, the field current of the synchronous motor is compared with a reference value jf and a detected value, and a field voltage reference is obtained by the amplifier 10 according to the deviation, and the field power converter 4 is driven.

As described above, in this embodiment, the voltage reference of the synchronous motor is calculated on the dq axis, and the coordinate converter converts this into a three-phase alternating current amount. This allows various control quantities to be handled by direct current, so the current can be controlled accurately even at high drive frequencies, making it possible to realize a drive device with good performance over a wider speed range and wider load range than conventional methods. .

FIG. 3 is a block diagram showing another embodiment of the present invention. In the figure, 15 is a speed calculator, and 16 is a voltage calculator.

Other elements that are the same as those shown in FIG. 1 correspond to the same numbers. FIG. 4 shows a detailed configuration of the voltage calculator 16 shown in FIG. 3, and 161 and 162 are multipliers.

In this embodiment, the dq-axis current reference and the detected value are compared, and the amplifier 9 outputs udltVqx according to the deviation. The voltage calculator 16 is a block that performs back electromotive force compensation, and the amplifier 9
The ciq-axis voltage reference is output from the outputs of F and R, the dq-axis magnetic fluxes Φd, Φ9, and the speed ω.

In other words, the back electromotive force of the motor is in a direction that leads the magnetic flux by 90 degrees, and its magnitude is proportional to the electrical angular velocity ω and the magnitude of the magnetic flux, so this component is created as part of the voltage reference. The electrical angular velocity ω is calculated by differentiating the position signal and using the velocity calculator 1.
5.

Due to the above operation, the output of the amplifier 9 only needs to be a voltage corresponding to a change in armature current or armature winding resistance.

Therefore, this portion provides an output with a relatively small amplitude, and more stable control can be achieved than in the embodiment shown in FIG.

〔Effect of the invention〕

As explained above, in the present invention, the armature current of the motor can be controlled accurately even under relatively high drive frequencies and heavy load conditions, and a high-performance variable speed drive device for a synchronous motor can be realized.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 is a block diagram of the magnetic flux calculator shown in the figure, FIG. 3 is a configuration diagram showing another embodiment of the present invention, FIG. 4 is a detailed configuration diagram of the voltage calculator of FIG. 3, and FIG. 5 is a conventional example. FIG. 1...Power converter 2...Synchronous motor 3...
・Position detector 5...Position calculator 7...Current calculator 9.10...Amplifier 13...DQ axis current calculator 4...Field power converter 6...Magnetic flux calculation Device 8.14...Coordinate converter 11, 12...Current detector

Claims (1)

[Claims] In a synchronous motor control device that controls a three-phase synchronous motor at variable speed using a variable voltage variable frequency power source, a current detector detects an armature current of the synchronous motor, and a position detector detects a rotor position of the synchronous motor. and a current calculator that calculates a current component of the current from the current detector in the same direction as the magnetic poles of the rotor (d-axis) and in a direction (q-axis) perpendicular to the magnetic poles of the rotor, based on the signal from the position detector; a field current detector that detects a field current of the synchronous motor; a magnetic flux calculator that calculates the magnetic flux of the synchronous motor from the outputs of the current calculator and the field current detector; and a torque to the synchronous motor. A current command calculator that calculates the d-axis and q-axis current command signals of the synchronous motor from the current command signal and the magnetic flux calculator, and a deviation between the output signal of the current command calculator and the output signal of the current detector. a coordinate converter that outputs a three-phase armature winding voltage reference signal from the voltage reference signals on the d-axis and q-axis obtained from the position detector and the signal from the position detector; A control device for a synchronous motor, characterized in that control is performed based on a three-phase armature winding voltage reference signal.