KR940006964B1 - Arrangement for speed regulation of electric motor - Google Patents

Abstract

The apparatus for controlling speed of an induction motor comprises an induction motor, a microprocessor, a first analog-to-digital (A/D) converter for converting a normal speed command value to digital data, an encoder for sensing the current speed of the induction motor, a hall sensor for sensing 2-phase current, a current operator for performing the operation of the 1-phase current, a second A/D converter connected to the current operator, a D/A converter, a current controller, a comparator for comparing the control value of the current controller with a triangular wave, a pulse width modulating signal distributor for distributing pulse width modulating signal, a low-pass filter for passing only a low frequency band of the distributed pulse width modulating signal, a third A/D converter, and an inverter for supplying the 3-phase current to the induction motor, thereby maintaining a normal speed.

Description

Speed control device and control method of induction motor

1 is a speed control circuit diagram of a conventional induction motor.

2 is a control block diagram of a speed control device of the induction motor of the present invention.

3 is a flowchart showing a speed control method of the induction motor of the present invention.

* Explanation of symbols for main parts of the drawings

1: induction motor 2: encoder

7 microprocessor 10 current controller

12 comparator 13 pulse width modulated signal splitter

15 low pass filter 18 inverter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device and a speed control method of an induction motor that control an induction motor by a nonlinear control method. In particular, the phenomenon of interference between the rotor speed and the pore flux of an induction motor by a simple control method using a microprocessor is provided. The present invention relates to a speed control device and a control method of an induction motor by controlling the induction motor to maintain a steady state at all times.

In general, an induction motor is an AC motor without a commutator, and refers to a motor in which only one of a rotor or a stator is connected to a power source, and the other is a motor operated by inductor power. Recent advances in microelectronics and power electronics have led to the application of modern control theory to control induction motors.

In particular, the inversion of the microprocessor, which enables high-speed control operation, contributes to the simpler, more reliable and cheaper configuration of the induction motor control system.

The vector control method, a product of this technological development, has been used to obtain high performance dynamic characteristics of induction motors.

However, in the case of the vector control method, it is not easy to completely eliminate the interference phenomenon between the rotor speed and the magnetic flux of the induction motor, and in the case of realizing the control algorithm, the three-phase current for the axis fixed on the stator side. Is converted into a current on the dp axis rotating at an arbitrary speed, then controlled and converted again into a three-phase current for the fixed axis, and the converted three-phase current value must be applied to the induction motor through the inverter. There was a problem that is quite complicated.

As another example of the speed control device of the motor, there is a speed control device of the motor as shown in FIG. 1, but the device includes a power supply unit 29 for applying power to the motor 20 and the motor 20; A frequency generator 21 having a frequency corresponding to the number of revolutions of the motor 20 and generating a voltage having periodicity every half cycle, and a waveform shaping circuit 22 shaping an output waveform of the frequency generator 21. And the outputs of the first and second single-safe multivibrators 30 and the first and second single-stable multivibrators 30 and 31 that operate in accordance with the output of the waveform shaping circuit 22. OR circuit 32, a third monostable multivibrator 23 operating according to the output of the OR circuit 32, a reference oscillator 24 for generating a pulse voltage of a predetermined frequency, and the reference Phase comparison between the output of the oscillator 24 and the output of the OR circuit 32 Has a phase comparator 25, an adder 26 that adds an output of the phase comparator 25 and an output of the third monostable multivibrator 23 to smoothly amplify the output of the adder 26. The motor 27 is provided with an amplifier 27 and a speed control circuit 28 for controlling the speed of the motor 20 by the output signal amplified by the amplifier 27 to control the motor. The speed control device has the advantage of improving the characteristics of the control system, but has a disadvantage that the configuration of the control system is relatively complicated, the operation can not be easily performed.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to obtain dynamic characteristics by eliminating interference between rotor speeds and air gap magnetic fluxes of an induction motor, and at the same time, according to coordinate transformation in vector control. The present invention provides a speed control device and a control method of an induction motor that removes a computation amount and controls the induction motor.

In order to achieve the above object, the speed control apparatus of an induction motor according to the present invention includes an induction motor, a microprocessor operative to perform non-interference control between the rotor speed and the air gap of the induction motor, and the normal speed of the induction motor. A first A / D converter for converting a command value into digital data, an encoder for detecting a current speed of the induction motor, a hall sensor for sensing a two-phase current among three phase currents applied to the induction motor, and the hall A current calculation unit which calculates the remaining one-phase current using the current sensed by the sensor and then inversely converts it, a second A / D converter which converts the stator current calculated by the current operation unit into digital data, and a void flux An A / D converter for converting a digital data value for speed control of an induction motor calculated by a microprocessor into an analog signal, A current controller for controlling the current based on the analog value, a comparator for receiving the control value of the current controller and comparing it with a triangular wave, and a pulse width modulation signal splitter for distributing the pulse width modulation signal generated based on the compared value. A low band filter for passing only the low frequency band of the divided pulse width modulation signal, a third A / D converter for converting the frequency value of the passed low frequency band into digital data, and the distributed pulse width modulation signal; It characterized by consisting of an inverter for applying a three-phase current to the induction motor by using.

In addition, the speed control method of the induction motor according to the present invention compares the normal speed command value and the encoder pulse value of the induction motor to determine the current speed of the induction motor and the stator using the detected phase current of the induction motor The second step of calculating the current and then converting the digital data into a microprocessor and inputting the microprocessor, and the third step of calculating the stator voltage after converting the pulse width modulated signal passing through the low pass filter into digital data. And a fourth step of generating a nonlinear control value by proportionally integrating the speed and the magnetic flux based on the pore flux value calculated by the current speed, stator current and stator voltage of the induction motor, and fixing the nonlinear control value to the stator shaft. A fifth step of generating a basic pulse width modulated signal by converting the current signal into a three-phase value on an axis; It is characterized in that the sixth step to control the induction motor by applying to the inverter after the distribution.

According to the speed control device and control method of the induction motor of the present invention, an induction motor as an actuator of a system requiring high performance dynamic characteristics such as an industrial robot or a computer numerical control (CNC) machine tool, etc. In addition to making it possible to use, it can be used in dusty or explosion-proof environments where direct current motors cannot be used, and can be used to control induction motors for operating rolling mills, rotary presses, and elevators. In addition, the induction motor can be controlled to have excellent transient characteristics and steady state.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 2 is a control block diagram of a speed control apparatus of an induction motor of the present invention, and FIG. 3 is a flowchart of a speed control method of the induction motor of the present invention.

2, (1) is a three-phase induction motor composed of a stator and a rotor, (2) is an encoder that detects the current speed of the induction motor 1 and generates a pulse corresponding to the speed. (3) is a first analog-to-digital converter (hereinafter referred to as a first A / D converter) that receives the normal speed command value of the induction motor 1 and converts it into digital data. (4) is a Hall sensor for detecting a two-phase current of the three-phase current applied to the induction motor (1), (6) is a current calculation unit for calculating the two-phase current sensed by the Hall sensor (4), (5) is a second A / D conversion unit for converting the axial current (ia, ib) of the stator calculated by the current operation unit 6 into digital data, and (7) is a normal of the induction motor (1) The error value comparing the speed command value (Wr *) and the current speed value (Wr) and the air gap flux command value ( *) And the pore flux calculated using the X and Y axis currents (ixs, iys) and stator voltages (Va, Vb) of the stator. ) Is a microprocessor that calculates the basic command value of the three-phase current command value for controlling the induction motor by proportionally integrating and controlling the error value, and the microprocessor 7 includes the air gap magnetic flux calculation unit 71 and the speed and magnetic flux. It is comprised of the proportional integral P1 control part 72, the nonlinear control part 73, and the conversion part 74. As shown in FIG. (8) is for speed control of the induction motor (1) calculated by the microprocessor (7) Awards and A / D conversion unit for converting the digital data of the phase into an analog signal, respectively (10) is a three-phase current based on the analog value of the speed of the induction motor (1) converted by the A / D conversion unit (8) A current controller for controlling, and (12) is a comparator for comparing the triangular wave with the current value controlled by the current controller 10.

(13) is a pulse width modulated signal divider for receiving the output signal of the comparator 12 and modulating the pulse width and distributing it into six pulse width modulated signals, and (15) the pulse width modulated signal divider 13 Is a low band filter that passes only the frequencies of the low frequency band among the signals distributed by (16), and (16) converts the frequency values of the low frequency band passed by the low band filter 15 into digital data so that the stator voltage can be calculated. The third A / D converter outputs voltage signals Va and Vb. (18) applies the three-phase currents (ia, ib, ic) to the induction motor (1) using the six pulse width modulation signals distributed by the pulse width modulation signal splitter (13) to apply the induction motor (1). It is an inverter to control.

In the speed control apparatus of the induction motor according to the present invention configured as described above, first, it is required to discriminate the air gap magnetic flux by using the magnetic flux measuring sensor of the induction motor 1 or any magnetic flux estimation method. As an example of the magnetic flux estimation method, There is a method of determining the rotor flux first and then obtaining information on the air gap flux from the following general equation.

In fact, the nonlinear control method for performing non-interference control between rotor speed and air gap flux is as follows.

(2)

remind Is converted into a value on the a, b, and c axes fixed to the fault magnetic axis by the following equation, and then is compared with the triangular wave in the comparator 13 to generate a pulse width modulated signal.

A, b, c, the three-phase value on the axis

(3)

Is computed as

Accordingly, the generated pulse width modulated signal is divided into six signals by the pulse width modulated signal generator 13 and then applied to the inverter 18 (transistor, MOS-FET, thyristor may be used) and the induction motor. At the same time as controlling (1), stator voltages Va and Vb passing through the low band filter 15 and the third A / D converter 16 are applied to the magnetic flux calculation unit 71 so that the stator current i _xs , i _ys ) And void magnetic flux ( Is used to compute

On the other hand, after detecting the two-phase current (ia, ib) of the three-phase current (ia, ib, ic) of the induction motor (1) by the Hall sensor (4), calculates the remaining one-phase current (ic) and reverse conversion again The X-axis current i _xs of the stator and the Y-axis current i _ys of the stator are obtained, and then converted into digital data by the second A / D converter 5 and input to the microprocessor 7.

In addition, the speed of the rotor of the induction motor 1 is detected by the encoder 2 to generate a pulse corresponding to the speed of the rotor, and is counted using a counter (not shown). Enter 7). Then, the first A / D converter 3 converts the digital data and compares the normal speed command value Wr * input to the microprocessor 7 to perform proportional integral control on the speed.

Next, the speed control method of the induction motor will be described with reference to FIG.

First, the normal speed command value Wr * of the rotor of the induction motor 1 input from the outside in step S1 is converted into digital data by the first A / D converter 3 to convert the microprocessor 7 into the digital data. The pulse value corresponding to the present speed value Wr of the rotor detected by the encoder 2 is input to the proportional integral controller 72 which proportionally integrates the speed and the magnetic flux. It is input to the integral control part 72.

Then, in step S3, the microprocessor 7 determines the current speed value of the induction motor 1, and the flow proceeds to step S4 by the Hall sensor 4 for the current of two phases of the three-phase current of the induction motor 1. After detecting (ia, ib) and calculating the remaining one-phase current (ic) using the detected current (ia, ib) in step S5, the equation (3) is inversely transformed to obtain the stator's x-axis current (i _xs ) and y-axis current i _ys are calculated.

Next, the flow proceeds to step S6, where the x-axis current i _xs and y-axis current i _ys of the stator are converted into digital data by the second A / D converter 5, respectively, and the converted digital data. Is inputted to the proportional integral control unit 72 of the microprocessor 7 in step S7, and the six basic pulse width modulation signals output from the pulse width modulation signal generator 13 pass through the low band filter 15 in step S8. After that, in step S9, the third A / D conversion unit 16 converts the data into digital data to obtain the stator voltages Va and Vb. Accordingly, in step S10, the magnetic flux calculation unit 71 in the microprocessor 7 uses the stator voltages Va and Vb as well as the X axis current i _xs and the y axis current i _ys of the stator. _{xg yg xs ys} , ) Is proportionally integrated. In step S12, the nonlinear control unit 73 Is generated and the conversion unit 74 converts the three-phase values Ua, Ub, and Uc in step S13.

Next, in step S14, only Ua and Ub of the three-phase values Ua, Ub, and Uc are converted into analog signals by the A / D converter 8, and then input to the current controller 10, and the comparator 12 In step S15, the basic pulse width modulated signal of step S15 is generated in comparison with the triangular wave, which is divided into six signals by the pulse width modulated signal distributor 13 in step S16.

Accordingly, the divided six signals are applied to the inverter 18 in step S17, and then generate a three-phase current for controlling the induction motor 1 to control the induction motor 1 in step S18.

As described above, according to the speed control apparatus and control method of the induction motor of the present invention, the high performance dynamic characteristics are obtained at all times by eliminating the interference phenomenon between the rotor speed and the pore flux of the induction motor by a simple control method using a microprocessor. It is effective to maintain the optimum efficiency by maintaining the.

Claims (4)

An induction motor, a microprocessor operative to perform non-interference control between the rotor speed and the air gap of the induction motor, a first A / D converter for converting the normal speed command value of the induction motor into digital data; After calculating the remaining one-phase current by using the encoder for detecting the current speed of the induction motor, the home sensor for detecting the three-phase current of the three-phase current applied to the induction motor, and the current sensed by the home sensor Digital data for speed control of an induction motor calculated by a microprocessor using a current processor for inverse conversion, a second A / D converter for converting a stator current calculated by the current calculator into digital data, and a void flux An A / D converter for converting a value into an analog signal, a current controller for controlling a current based on the converted analog value, and a control of the current controller A comparator for receiving a value and comparing it with a triangular wave, a pulse width modulation signal divider for distributing a pulse width modulation signal generated based on the compared value, a low band filter for passing only a low frequency band of the divided pulse width modulation signal; And a third A / D converter for converting the frequency value of the passed low frequency band into digital data, and an inverter for applying a three-phase current to an induction motor using the divided pulse width modulation signal. Speed control device of the motor. The speed control apparatus of claim 1, wherein the microprocessor includes an air gap magnetic flux calculation unit, an extraordinary integral control unit that proportionally integrates the speed and the magnetic flux, a nonlinear control unit, and a conversion unit. The first step of judging the current speed of the induction motor by comparing the normal speed command value of the induction motor with the encoder pulse value, and calculating the stator current using the detected phase current of the induction motor and converting it into digital data A second step of inputting to the second step; a third step of calculating a stator voltage by converting the pulse width modulated signal passing through the low pass filter into digital data; A fourth step of generating a nonlinear control value by proportionally integrating the speed and the magnetic flux based on the air gap magnetic flux value calculated by the stator voltage, and converting the nonlinear control value into a three-phase value on the axis fixed to the stator shaft and then controlling the current. A fifth step of generating a basic pulse width modulated signal and the pulse width modulated signal are distributed and applied to the inverter to control the induction motor. Induction rate control method of the motor which is characterized by being a sixth step for. 4. The speed control method of an induction motor according to claim 3, wherein the pulse width modulated signal passing through the low band filter is a low frequency band and is a frequency required for stator voltage calculation.