KR100256315B1 - A apparatus of slip frequency type vector control for in duction motor - Google Patents

Abstract

PURPOSE: A slip frequency vector control apparatus of an induction motor is provided to compensate the rotor time constant of the induction motor controlled by an inverter of slip frequency vector control method, thereby preventing the degradation of a vector controller due to the variance of the rotor time constant. CONSTITUTION: A speed controller(1) receives a signal which subtracted the speed of an induction motor(8) from an externally transferred speed command value, and outputs a torque current command value. A current transformer(6) transforms the d, q currents(ia,ib) of a stator into rotation coordinates to output stator current(ids,iqs). A current controller(2) receives torque current and magnetic flux current from a vector control inverter(7) to output a magnetic flux voltage command value and a torque voltage command value through a rotation coordinate control circuit. A coordinate converter(4) receives the magnetic flux voltage command value and torque voltage command value and converts the coordinates of the values to output voltage command values(Va,Vb,Vc). The vector control inverter(7) receives the voltage command values(Va,Vb,Vc) to apply voltage to the induction motor(8). A slip operator(3) output slip frequency(Wsl). An integrator(5) integrates stator appliance frequency(We) to output the position of rotor magnetic flux to the coordinate converter(4) and current transformer(6). A time constant estimator(100) estimates the variance of time constant of the vector control inverter(7) to output a rotor time constant compensating signal to the slip operator(3).

Description

Slip frequency type vector control device for induction motors

The present invention relates to an induction motor, and in particular, compensates the rotor time constant of an induction motor controlled by an inverter of a slip frequency vector control method so that the performance of the vector controller is degraded as the rotor time constant is changed by a long time operation. The present invention relates to a slip frequency type vector control apparatus of an induction motor, which is intended to prevent the occurrence of a defect.

In general, the slip frequency type vector control device of an induction motor is a device that independently controls each other so as not to interfere with each other by converting the three-phase variable values flowing in the induction motor into the d, q axis orthogonal to each other.

In the conventional induction motor slip frequency type vector control apparatus, as illustrated in FIG. 1, the speed Wr of the induction motor 8 detected by the speed detector 9 is subtracted from the speed command value Wr * transmitted from the outside. Speed controller (1) that receives the received signal and outputs torque current command value (iqs *), and induction motor (8) converts the st and d currents (ia, ib) of the stator to the rotational coordinate system to stator current ids and In the current converter 6 which outputs iqs, and the vector control inverter 7 separately controlled by the magnetic flux and torque, the magnetic flux current (ids *) and the torque current command value (iqs *) for the operation of the constant torque range. A current controller (2) receiving the torque component and the flux component current subtracted from the stator currents ids and iqs, respectively, and outputting the magnetic flux component voltage command value Vds * and the torque component voltage command value Vqs * through the rotational coordinate control circuit, respectively; And the magnetic flux voltage command value Vds * and the torque voltage Coordinate converter 4 that receives the command value Vqs * and converts the coordinates to output voltage command values Va, Vb, Vc, and the voltage command values Va, Vb, Vc to the induction motor 8. A vector control inverter 7 for applying a voltage, a slip calculator 3 for outputting a sleep frequency Wsl with values input to the stator current ids and iqs and the vector control inverter 7, and the sleep frequency ( The speed Wr detected by the speed detector 9 is added to Wsl) to integrate the input stator applied frequency We, and thus to determine the rotor flux used in the coordinate converter 4 and the current converter 6. It consists of the integrator 5 which outputs the position (theta).

Referring to the operation of the conventional vector control device configured as described above are as follows.

First, the speed controller 1 receives the torque current command value iqs * when a signal obtained by subtracting the speed Wr of the induction motor 8 detected by the speed detector 9 from the speed command value Wr * transmitted from the outside is input. ) Will be printed.

The current transformer 6 converts the st, d-side currents (ia, ib) of the stator in the induction motor 8 into the rotational coordinate system using the position (θ) of the rotor magnetic flux output from the integrator 5. Outputs current ids and iqs.

Then, the stator current ids is subtracted from the flux current (ids *) for the operation of the constant torque region in the vector control inverter 7 separately controlled by the flux content and the torque content, and the stator current at the torque current command value iqs *. Each of iqs is subtracted so that the torque component and the flux component current are input to the current controller 2.

Next, the current controller 2 outputs the magnetic flux voltage command value Vds * and the torque voltage command value Vqs * through the rotational coordinate control circuit, respectively, and the coordinate converter 4 receives the integrator 5 The coordinates are converted using the position (θ) of the rotor magnetic flux outputted by) to output the voltage command values Va, Vb, and Vc.

Then, the vector control inverter 7 receives the voltage command values Va, Vb, and Vc to apply the voltage to the induction motor 8.

On the other hand, the slip operator 3 receives the constants obtained by testing the stator current ids and iqs and the induction motor 8 output by the current converter 6, and outputs a slip frequency Wsl. When the speed Wr detected by the speed detector 9 is added to Wsl), the integrator 5 integrates this signal to the position of the rotor magnetic flux used for the coordinate converter 4 and the current converter 6. θ) will be output.

However, in the slip frequency type vector control apparatus of the conventional induction motor, the values used for the slip operator are set after the induction motor is tested and the necessary constants are obtained before the induction motor is operated. The constants of the induction motors obtained at this time are values that are changed by heat generation during operation.

Therefore, when the slip frequency is generated using the stator current value obtained by the current converter and the values input to the inverter, the vector control device has a problem in that the control performance in the transient state and the normal state is degraded.

Accordingly, an object of the present invention is to compensate for the rotor time constant of an induction motor controlled by an inverter of a slip frequency vector control method, that is, to estimate and compensate for a change generated during operation of induction motor constants used in a slip operation, for a long time of operation. The present invention provides a slip frequency type vector control apparatus for an induction motor which prevents the performance of the vector controller from deteriorating as the rotor time constant changes.

Technical means of the present invention for achieving the above object, in the induction motor including a vector control inverter for controlling the speed of the motor based on the magnetic flux voltage command value, the torque voltage command value and the slip frequency, the induction motor test A slip calculation unit for outputting a slip frequency using the rotor time constant compensation signal obtained by the stepwise and the stator current of the induction motor indicated by the rotary coordinate system, and a voltage command value of the magnetic flux and the torque component indicated by the stator current and the rotary coordinate system, respectively. A compensation function generator that receives the output of the compensation function, a reference function generator that outputs a reference function using the rotor flux induced voltage and torque component induced voltage of the induction motor, and a compensation function from the compensation function generator and the reference function generator. The slip after correcting the error by comparing the input and the reference function respectively And a rotor time constant estimator including a slip compensation controller for outputting a rotor time constant compensation signal to a calculation unit to compensate for the rotor time constant of the vector control inverter.

1 is a block diagram showing a slip frequency type vector control apparatus of a conventional induction motor,

2 is a block diagram showing a slip frequency type vector control apparatus of an induction motor according to the present invention;

3 is a block diagram illustrating a detailed circuit of the rotor time constant estimation unit illustrated in FIG. 2.

Explanation of symbols on the main parts of the drawings

100: rotor time constant estimator 101: compensation function generator

102: reference function generator 103: error determiner

104: multiplier 105: slip compensation controller

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing a slip frequency type vector control apparatus of an induction motor according to the present invention, wherein the speed Wr of the induction motor 8 detected by the speed detector 9 at a speed command value Wr * transmitted from the outside is shown. The speed controller 1 receives the subtracted signal) and outputs the torque current command value (iqs *), and the induction motor 8 converts the st and d currents of the stator (ia, ib) into a rotational coordinate system. In the current converter 6 which outputs current ids and iqs, and in the vector control inverter 7 separately controlled by the magnetic flux and the torque, the magnetic flux current (ids *) and the torque current command value (iqs) for the operation of the constant torque range. *) The current controller receives the torque component and the flux component current subtracted from the stator current ids and iqs, respectively and outputs the magnetic flux component voltage command value (Vds *) and the torque component voltage command value (Vqs *) through the rotation coordinate control circuit. (2) and the flux voltage command value (Vds *) Coordinate converter 4 that receives the oak component voltage command value Vqs * and converts coordinates to output voltage command values Va, Vb, Vc, and the voltage command values Va, Vb, Vc. 8) a vector control inverter 7 for applying a voltage to it, a slip calculator 3 for outputting a sleep frequency Wsl with values input to the stator current ids and iqs and the vector control inverter 7, and the sleep Rotor used for the coordinate converter 4 and the current converter 6 by integrating the input stator applied frequency We by adding the speed Wr detected by the speed detector 9 to the frequency Wsl. The integrator 5 outputting the magnetic flux position θ, the stator current ids and iqs, the magnetic flux voltage command value Vds * and the torque voltage command value Vqs * are inputted. The rotor for estimating the rotor time constant variation and outputting the rotor time constant compensation signal to the slip operator 3 It has been composed of a constant estimation unit (100).

In addition, the rotor time constant estimation unit 100 according to the present invention, as shown in Figure 3, the voltage command value (Vds *) and the voltage command value (Vqs *) of the torque for the magnetic flux represented by the rotational coordinate system and the stator Compensation function generator 101 for receiving currents ids and iqs and outputting a compensation function, and a reference function for outputting a reference function using the rotor flux induced voltage and the torque induced induced voltage of the induction motor 8. The generator 102 and the error determiner 103 for subtracting the reference function from the compensation function and determining the sign and outputting a positive signal when the signal is positive and a negative signal when the signal is negative, and the error judgment And a slip compensation controller 105 which receives a signal obtained by subtracting the reference function from the output signal of the device 103 and the compensation function through the multiplier 104 and compensates the rotor time constant of the vector control inverter 7. have.

Referring to Figures 2 and 3 attached to the operation and effect of the present invention configured as described above are as follows.

First, look at the state equation of the stator voltage in the induction motor (8) as shown in Equation 1 below.

Here, when the voltage equation of the induction motor 8 represented by the orthogonal rotor coordinate system d and q-axis is obtained from Equation 1, Equation 2 below is obtained.

In addition, the slip frequency used in the rotor flux equation and the slip calculator 3 from Equation 1 may be represented by Equations 3 and 4, respectively.

In the induction motor 8, the vector control device converts the three-phase variable values flowing in the induction motor into d and q axes that are orthogonal to each other to independently control each other so that interference does not occur. In this case, the induction motor 8 For speed control, the flux flux current ids of the stator current is made constant, and the torque current iqs is controlled to control the speed.

Under these conditions, if the axis of the rotor magnetic flux coincides with the d axis of the rotary coordinate system rotating at the same speed as the frequency applied to the induction motor 8, the magnetic flux on the d axis becomes the magnetic flux of the induction motor 8, and the magnetic flux on the q axis. The minute may assume the condition of Equation 5 below, which does not exist.

Here, when the slip frequency Wsl and the rotor magnetic flux equation of the slip operator 3 are obtained using the condition of Equation 5, Equations 6 and 7 are shown.

On the other hand, the stator voltage equation represented by the d, q axis in the rotational coordinates is expressed as shown in Equation 8 below.

In the slip calculator 3, the slip frequency Wsl is generated as the flux current ids, the torque current iqs, and the rotor time constant Tr indicated by the rotational coordinate system.

At this time, the rotor time constant (Tr) is represented by the ratio of the rotor inductance and the rotor resistance of the induction motor (8), these values are values that vary as the induction motor (8) operates, the value of the vector control inverter (7) It affects the control performance.

Therefore, in the present invention, the variation of the rotor time constant Tr is estimated and compensated based on the stator voltage equation of Equation 8 to improve the control performance of the vector control apparatus.

Obtaining the rotor induced voltage equation in Equation 8 is shown in Equations 9 and 10 below. In this case, the torque induced voltage is defined as e _T , and the flux induced voltage is defined as e _M.

When the conditions of Equation 5 are substituted by Equations 9 and 10, Equations 9 and 10 of the vector control inverter 7 are represented by Equations 11 and 12 below.

The conditions satisfied by Equations 11 and 12 can be regarded as the conditions under which the slip frequency calculation of the vector control inverter 7 is accurate and the stator current components are independently controlled in terms of torque.

In addition, when using Equations 9 and 10 as the reference function for compensating the variation of the rotor time constant (Tr), since the right side includes the term of the stator resistance Rs, this value is also changed by operating the induction motor (8). Since the value is used in the present invention, the product of Equations 9 and 10 is used as a reference function. If the reference function is defined as F * and the compensation function is defined as F, the following equations (13) and (14) are shown.

Meanwhile, the compensation function generator 101 detects the voltage command value Vds * for the magnetic flux represented by the rotational coordinate system, the voltage command value Vqs * for the torque, and the stator currents ids and IQs to detect the stator of the stator indicated by the rotor coordinate system. The compensating function F is generated by the magnetic flux and torque component currents. In this case, the compensation function F uses Equation 13.

The reference function generator 102 generates the reference function F * from Equation 14. In this case, Equation 14 is used.

In this case, the error determiner 103 outputs a positive signal when the phase of the stator applied frequency is positive, and outputs a negative signal when the phase of the stator applied frequency is positive. As shown in Equation 14, since the reference function F * includes the term of the stator applied frequency (We), it must be multiplied by the sign of We so that the reference function F * and the compensation function F are independent of the direction of rotation of the induction motor 8. It is possible to use.

Then, the output signal of the error determiner 103 and the signal obtained by subtracting the reference function F * from the compensation function F are input to the slip compensation controller 105 via the multiplier 104 to rotate the rotor of the vector control inverter 7. It is used as the value of time constant (Tr). That is, the reciprocal of the rotor time constant Tr used in the slip operator 3 is compensated during the operation of the induction motor 8.

On the other hand, the voltage of the stator differs from the setpoint voltage at any time for Va, Vb, Vc output through the coordinate converter 4 to prevent arm short of the switching element used in the vector control inverter 7. Since the dead time is added to add the dead time compensation circuit to the vector control inverter 7, the command value of the stator voltage and the actual stator voltage are made equal.

Therefore, as described above, the constant values of the induction motor used in the slip operator are variable constants generated by the induction motor operation. In the present invention, the constant values of the induction motor during the operation using the rotor time constant estimator are used. By estimating and compensating for the change, the position (θ) of the axis of the rotor flux used to convert to the rotational coordinate system is accurately obtained. Therefore, the response time of the current controller and the speed controller is improved, and the rotor time constant is changed by long time operation. The performance of the controller can be prevented from deteriorating.

Claims (1)

In an induction motor including a vector control inverter for controlling the speed of the motor based on the magnetic flux voltage command value, the torque voltage command value and the slip frequency, A slip calculation unit for outputting a slip frequency using a rotor time constant compensation signal obtained by testing the induction motor and a stator current of the induction motor indicated by a rotational coordinate system; And A compensation function generator that receives the voltage command values of the magnetic flux and torque components indicated by the stator current and the rotational coordinate system, respectively, and outputs a compensation function, and a reference function using the induced flux voltage and the torque component induced voltage of the induction motor. The vector control inverter outputs a rotor time constant compensation signal to the slip operation unit after correcting an error by receiving and comparing a compensation function and a reference function from the reference function generator and the compensation function generator and the reference function generator, respectively. Slip frequency type vector control apparatus of an induction motor, characterized in that it comprises a rotor time constant estimation unit including a slip compensation controller to compensate for the rotor time constant of the motor.

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