JPH0710200B2 - Induction motor controller - Google Patents

Description

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 figure, the converter 1 includes a converter main circuit such as an inverter and a current control circuit, and by inputting a current command value ia ^{* to} ic ^* of each phase of the induction motor, a current according to the command value is obtained. It is supplied to the electric motor (motor) 2. In order to carry out such control, the torque command value τ ^* and the secondary magnetic flux command value φ ₂ ^* are used to excite the secondary magnetic flux of the primary current in parallel with the following equations (1) and (2). Current command value i _M ^* of current component and current command value i _T of torque current component perpendicular to it
^* Is calculated and well-known vector control is performed based on this.

T _2: conducting machine secondary time constant, M: 1 primary motor secondary mutual inductance ^{_{i T * = τ * / φ}} 2 * ...... (2) arithmetic circuit 3 calculates the (1), divided The instrument 4 executes the division of the equation (2). The coordinate converter 5 converts the quantities (i _T ^* , i _M ^* ) of the secondary magnetic flux coordinate system into the quantities (ia ^* , ib ^* , ic) of the stator coordinate system.
^* ), Where the angle between the a-phase winding of the stator and the secondary magnetic flux is ₂ , the conversion is performed by the following equation (3).

[Problems to be Solved by the Invention] In the electric motor, the relationship between the exciting current component i _M parallel to the secondary magnetic flux and the secondary magnetic flux φ ₂ is a first-order lag from the equation (1) as follows.

Conventionally, a differential term is added to the calculation of i _M ^* as shown in equation (1) so that the desired maximum torque can be generated by matching the command value and the actual value of the secondary magnetic flux φ ₂ even during a transition (during motor acceleration). (If there is no differential term, i _M ^* will be a constant value, and as a result, the actual magnetic flux will have a first-order lag with respect to the command value from equation (4), so the torque generated will also have a time constant relative to the command value. It will be the first delay of T _2. )

However, even in a steady state, φ ₂ ^* fluctuates due to uneven rotation of the electric motor (rotation ripple), so i _M ^* 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 significant. As a result, the control system of the component i _T perpendicular to the secondary magnetic flux is also interfered, and the torque fluctuates.

Therefore, an object of the present invention is to prevent the calculation command value of the exciting current from largely changing due to the uneven rotation of the electric motor during the steady state of the motor so that the torque fluctuation does not occur.

[Means for Solving the Problems]

Deviation calculation means for calculating the deviation between the speed command value and the speed detection value, comparison means for comparing the speed deviation obtained by the deviation calculation means with a predetermined value, and an exciting current command value for the secondary magnetic flux. And an exciting current command value calculating means for outputting the result of the selection based on the output signal from the comparing means.

[Action]

When calculating the excitation current command value, the calculation including the differential term is performed during the motor acceleration, and the calculation does not include the differential term during the steady state, so that the maximum capacity of the motor is exhibited during the acceleration of the motor and stable operation is achieved during the steady state. It can be so.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In the conventional example shown in FIG. 2, an arithmetic circuit 3A, a speed detector 6, a switching switch 7, a subtractor 8, a setter 9, a comparator 10 and the like are shown. It is configured by adding.

The switching switch 7 uses the current command value i _M ^* of the exciting current component parallel to the secondary magnetic flux of the primary current as the output of the circuit 3 for calculating the above equation (1). It is provided to switch whether to be the output of the circuit 3A for calculating the deleted equation (5).

The switching signal S of the switching switch 7 is the output of the subtractor 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 value set in advance by the setter 9. The output of the comparator 10 for comparing and is shown. Therefore, when the speed deviation is larger than the predetermined value, the output of the arithmetic circuit 3 is switched to the side to be i _M ^* , otherwise, the output of the arithmetic circuit 3A is to the side to be i _M ^*. It can be switched.

By doing so, the maximum capacity of the electric motor can be exhibited during acceleration of the electric motor, and the electric motor can be stably driven during steady operation.

〔The invention's effect〕

According to the present invention, when the motor speed is large (eg 100 rpm or more) and the motor is accelerating (transient), a differential term is inserted in the calculation of i _M ^* , and when the speed deviation is small (eg 100 rpm or less) (steady state) Since the differential term is not included, the maximum motor performance can be exhibited during motor acceleration (transition), and the motor can be driven stably during steady operation.

[Brief description of drawings]

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. Explanation of symbols 1 ... Power conversion device, 2 ... Induction motor, 3,3A ... Arithmetic circuit, 4 ... Divider, 5 ... Coordinate converter, 6 ... Speed detector, 7 ... Switching switch, 8 ... Subtractor, 9 ... Setting device, 10 ... Comparator.

Claims (1)

[Claims] 1. A primary current of an induction motor is divided into an exciting current component parallel to a secondary magnetic flux and a torque current component orthogonal to the exciting current component, and torque control of the induction motor is performed so that each current component conforms to its command value. In the induction motor control device to perform, a deviation calculating means for calculating a deviation between the speed command value and the speed detection value, a comparing means for comparing the speed deviation obtained by the deviation calculating means with a predetermined value, and Based on the output signal from the comparison means, select whether to obtain the exciting current command value by performing an operation including differentiation from the secondary magnetic flux, or as a constant proportional to the secondary magnetic flux,
An induction motor control device comprising: an exciting current command value calculating means for outputting the result;