JPH0246190A - Induction motor control device - Google Patents

Abstract

PURPOSE:To bring the maximum capacity of a motor in full play in accelerating the motor, but in a steady state to drive the motor stably by including differential terms in the operation of exciting current in the motor acceleration, but in the steady state by including no differential terms. CONSTITUTION:An arithmetic circuit 3 performs the operation including differential terms. An arithmetic circuit 3A performs the operation including no differential terms. A comparator 10 compares the output of a subtractor 8 to operate the deviation of a speed detection value N detected by a speed detector 6 from a speed command value N* with a set value from a setter 9 and outputs a switching signal S of a changeover switch 7. Consequently, in case the speed deviation is greater than the predetermined value, the output of the arithmetic circuit 3 including the differential terms is outputted as an exciting current command value iM* In case it is not so, let the output of the arithmetic circuit 3A be iM*.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a control device for controlling an induction motor.

[Conventional technology]

FIG. 2 shows a conventional example of an induction motor control device.

In the same figure, a converter 1 includes a converter main circuit such as an inverter and a current control circuit, and by inputting current commands it, ~I0 of each phase of the induction motor, the command value and the current of the is supplied to an electric motor (motor) 2. In order to perform such control, the following (1) is calculated from the torque command value τ and the secondary magnetic flux command value φ2.
(2) According to (2), current torque control of the excitation current component parallel to the secondary magnetic flux of the -order current is performed.

M: primary and secondary mutual inductance of the motor The coordinate converter 5 converts the quantities (1, 1) of the secondary magnetic flux coordinate system into the quantities M (ia + 1b l IC) of the stator coordinate system, and the a-phase winding of the stator If the angle between the line and the secondary magnetic flux is 92,
Conversion is performed using the following equation (3).

[Problem to be solved by the invention]

In the electric motor, the relationship between the excitation current component IM parallel to the secondary magnetic flux and the secondary magnetic flux φ2 is a first-order lag according to equation (1) as shown in the following equation.

φ・″1+pT2i・−°−(“) Conventionally, in order to match the command value of the secondary magnetic flux φ2 with the actual value even during transient times (when the motor accelerates) and generate the desired maximum torque, (
1) A differential term is added to the IM operation as shown in formula (
There is no differential term! One is a constant value, and as a result, the actual magnetic flux will be a first-order lag with respect to the command value (as shown in equation (4)), so
The generated torque also has a first-order lag of time constant T2 with respect to the command value. ).

However, even in a steady state, φ2 fluctuates due to uneven rotation (rotational ripple) of the electric motor, and therefore φ2 may change significantly due to the differential term. In particular, since the frequency of rotation unevenness (rotation ripple) is high, the influence of differentiation is large. As a result, the control system for the component IT perpendicular to the secondary magnetic flux is also interfered with, resulting in a drawback that the torque fluctuates.

Therefore, it is an object of the present invention to prevent the calculation command value of the excitation current from changing greatly due to uneven rotation of the motor when the motor is steady, and to prevent torque fluctuations from occurring.

[Means to solve the problem]

a deviation calculation means for calculating the deviation between the speed command value and the speed detection value; a comparison means for comparing the speed deviation obtained by the deviation calculation means with a predetermined value; Exciting current command value calculation means for selecting whether to calculate the secondary magnetic flux by calculation including differentiation or to calculate it as a constant proportional to the secondary magnetic flux based on the output signal from the comparison means and outputting the result. establish.

[Effect]

When calculating the excitation current command value, the calculation is performed that includes a differential term when the motor is accelerating, and the calculation that does not include the differential term when the motor is steady. Be able to drive.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, in which an arithmetic circuit 3A, a speed detector 6, a changeover switch 7, a subtracter 8, a setter 9, a comparator 10, etc. Constructed by adding.

The changeover switch 7 is a circuit 3 that calculates the current command value of the excitation current component parallel to the secondary magnetic flux of the secondary current using the above equation (1).
or the following (by removing the differential term from equation (1))
5) It is provided to switch whether to use the output of the circuit 3A that calculates the equation.

The switching signal S of this switching switch f7 is determined by the output of a subtracter 8 that calculates the deviation between the speed command value N and the speed detection value N detected by the speed detector 6, and the output of the The output of the comparator 10 is shown for comparison with a predetermined value. Therefore, if the speed deviation is larger than a predetermined value, the output of the arithmetic circuit 3 is switched to the negative side; otherwise, the output of the three arithmetic circuits is switched to the negative side.
It can be replaced.

By doing so, the maximum capacity of the electric motor can be demonstrated when the electric motor is accelerating, and the electric motor can be driven stably when the electric motor is in steady state.

[Effect of the invention]- According to this invention, the speed deviation is large (for example, j 00
rpm or higher) when the motor is accelerating (transient), a differential term is included in the calculation of iM*, and when the speed deviation is small (for example, 100
Since the differential term is not included in the rotation speed (rpm or less) (in steady state), the motor can exhibit its maximum capacity during acceleration (transient time), and the motor can be driven stably in steady state.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional example of an induction motor control device. Description of symbols 1... Power converter, 2... Induction motor, 5°3A... Arithmetic circuit, 4... Divider, 5... ... Coordinate converter, 6 ... Speed detector, 7 ... Changeover switch, 8 ... Subtractor, 9 ... Setting device, 10. ...Comparator. Representative Patent Attorney Akio Namiki Representative Patent Attorney Kiyoshi Matsuzaki

Claims (1)

[Claims] The primary current of the induction motor is divided into an excitation current component parallel to the secondary magnetic flux and a torque current component orthogonal to this, and the torque of the induction motor is controlled so that each current component follows its command value. An induction motor control device that performs the following: a deviation calculation means for calculating a deviation between a speed command value and a detected speed value; a comparison means for comparing the speed deviation obtained by the deviation calculation means with a predetermined value; An excitation device that selects based on the output signal from the comparing means whether the excitation current command value is obtained by calculation including differentiation from the secondary magnetic flux or as a constant proportional to the secondary magnetic flux, and outputs the result. An induction motor control device comprising: current command value calculation means;