JP2009153288A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter estimating the inertia value of a device and the control constant of a speed controller in a short period with a high accuracy by a test run and automatically adjusting the control constant of the speed controller. <P>SOLUTION: The power converter includes an arithmetic means estimating a mechanical inertia value connected to a load by an acceleration/deceleration operation before an actual operation and correcting the control constant of a speed control section 21. In the power converter, the arithmetic means includes an inertia-estimate arithmetic section 24B estimating the mechanical inertia value by the acceleration/deceleration operation while computing the next acceleration/deceleration time on the basis of the estimated mechanical inertia value and a speed command preparation section 24A outputting a speed command value to the speed control section on the basis of the computed acceleration/deceleration time. In the power converter, the arithmetic means further includes a control-constant arithmetic section 24C correcting the control constant of the speed control section on the basis of the estimated mechanical inertia value. The accuracy of an estimation is improved by repeatedly estimating inertia. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power conversion device that estimates the inertia of a machine and corrects a control constant of a speed control unit in drive control of an electric motor such as an industrial machine (semiconductor manufacturing apparatus, machine tool, injection molding machine).

  Conventionally, the inertia value of the machine used to calculate the control constant of the speed controller is calculated based on the relationship between the generated torque of the motor, the acceleration / deceleration time, and the rotational speed by performing a test operation using a predetermined test operation pattern before actual operation. It is common to tune inertia. There is Patent Document 1 as a related document for estimating the mechanical inertia at the time of this trial operation.

JP-A-61-88780

  Even if the accuracy of inertia tuning is low in an induction motor, and even if the response is somewhat reduced, the induction motor will rarely step out due to rapid acceleration / deceleration. However, in a permanent magnet synchronous motor as an electric motor, the load torque is large or abrupt. When there is a significant change, it often falls out of the synchronization speed and falls into a state called out-of-step and becomes uncontrollable.

  The speed response is designed so as not to cause this step-out. However, if the inertia value deviates from the actual load inertia value at this time, it cannot be controlled with the designed response. In particular, in a sensorless operation that does not use a position sensor and a current sensor, information to be controlled is limited to resistance, inductance, induced voltage constant, and inertia motor constant. This motor constant error appears as a direct response error. Therefore, it is necessary to bring the motor constant used for control closer to the true value in order to realize a response as designed and, in turn, to realize stable control.

  In the trial run shown in Patent Document 1, if the trial run pattern is not appropriate, the torque current appears in the form of an overshoot, and if there is a catch on the motor itself or the load during the trial run, it becomes a disturbance and an accurate torque current is generated. It does not appear and it is difficult to obtain an accurate mechanical inertia value, and a long trial run time is required for trial and error.

  In the present invention, among the motor constants, the inertia tuning that affects the speed response is repeatedly tuned so that the error from the true value of the inertia value is minimized and stable control is realized in a short time. For the purpose.

  The present invention includes a power converter that drives an electric motor, a speed control unit that outputs a torque current command value according to a deviation between a speed command value and a speed detection value, and a current control unit that controls an output current according to the torque current command value And a power conversion device including a calculation unit that estimates a mechanical inertia value connected to a load by an acceleration / deceleration operation before actual operation and corrects a control constant of a speed control unit. An inertia estimated value calculation unit that estimates a mechanical inertia value and calculates a next acceleration / deceleration time based on the estimated mechanical inertia value, and a speed command value to the speed control unit based on the calculated acceleration / deceleration time. A speed command generating unit for outputting, and a control constant calculating unit for correcting a control constant of the speed control unit based on the mechanical inertia value estimated above are provided.

  Further, the inertia estimated value calculation unit sets the initial acceleration / deceleration time longer by adding a safety factor, calculates the subsequent acceleration / deceleration time based on the estimated mechanical inertia value, and the control constant calculation unit In preparation for acceleration / deceleration operation, the control constant of the speed controller is corrected based on the estimated mechanical inertia value.

  Further, the inertia estimated value calculation unit obtains an estimated ratio of the mechanical inertia values estimated in the previous and current acceleration / deceleration operations, and when the estimated ratio is within a predetermined range, the subsequent estimation is terminated, If there is not, the mechanical inertia value by the second acceleration / deceleration operation is estimated, and the control constant calculation unit corrects the control constant of the speed control unit based on the estimated ratio.

  Further, the inertia estimated value calculation unit obtains an estimated ratio of the mechanical inertia values estimated in the previous and current acceleration / deceleration operations, and determines that the mechanical inertia value has converged when the estimated ratio is within a predetermined range. Thereafter, the estimation is finished, and when the value is not within the predetermined range, the acceleration / deceleration operation is repeated until the mechanical inertia value converges to estimate the mechanical inertia value.

  Further, the inertia estimated value calculation unit obtains an estimated ratio of the mechanical inertia value estimated in the previous and present acceleration / deceleration operations, and when the estimated ratio exceeds a specified value, replaces the estimated ratio with a specified value, and the control constant The calculation unit corrects the control constant of the speed control unit based on the estimated ratio replaced with the specified value.

  The inertia estimated value calculation unit ends the operation when the acceleration / deceleration operation is repeated a predetermined number of times.

  The inertia estimated value calculation unit integrates the torque current during acceleration and deceleration during acceleration / deceleration operation, and calculates the motor and mechanical inertia from the difference between the accumulated value of the torque current during acceleration and the accumulated value of the torque current during deceleration. The acceleration torque used for the acceleration / deceleration is estimated, and the mechanical inertia value is estimated from the acceleration torque integrated value and the acceleration / deceleration time in the acceleration / deceleration operation.

The present invention includes a power converter that drives an electric motor, a speed control unit that outputs a torque current command value according to a deviation between a speed command value and a speed detection value, and a current control unit that controls an output current according to the torque current command value And a power conversion device including a calculation means for estimating a mechanical inertia value connected to a load by acceleration / deceleration operation before actual operation and correcting a control constant of the speed control unit,
The calculating means repeatedly calculates an acceleration / deceleration time for the next acceleration / deceleration time until the estimated mechanical inertia value converges, and sends a speed command value to the speed control unit based on the calculated acceleration / deceleration time. A speed command generation unit for outputting and a control constant calculation unit for correcting a control constant of the speed control unit based on a mechanical inertia value estimated by acceleration / deceleration operation are provided.

  The inertia estimated value calculation unit integrates the torque current during acceleration and deceleration during acceleration / deceleration operation, and calculates the motor and mechanical inertia from the difference between the accumulated value of the torque current during acceleration and the accumulated value of the torque current during deceleration. The acceleration torque used for the acceleration / deceleration is estimated, and the mechanical inertia value is estimated from the acceleration torque integrated value and the acceleration / deceleration time in the acceleration / deceleration operation.

  According to the present invention, since the acceleration / deceleration operation of the motor during the test operation automatically calculates the optimum operation time (pattern) and repeatedly estimates the mechanical inertia value, a highly accurate mechanical inertia value is efficiently obtained. Then, the control constant of the speed control unit is appropriately corrected.

A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a power converter according to an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes an electric motor for driving an industrial machine, which is composed of a permanent magnet synchronous motor or an induction motor. 20 is a power conversion device that supplies driving power to the electric motor 10, 30 is a current detector that detects currents (I _qc , I _dc ) supplied from the power conversion device 20 to the electric motor 10, and 40 is an actual rotation of the electric motor 10. It is a speed detector that detects the number (N). Here, the current detector 30 and the speed detector 40 pass current and speed information to the power converter 20 by direct measurement using a sensor or the like, or estimation processing when no sensor is used.

The power conversion device 20 includes a speed control unit 21 that outputs a torque current command value Iq ^* from a deviation between a speed command value N ^* and a speed detection value N from a calculation unit 24 described later, and a torque current command value Iq ^* and detection. Current control unit 22 that calculates voltage command values Vd ^* and Vq ^* from the detected torque current detection value Iqc, and voltage control unit that calculates the output of power converter 20 from the calculated voltage command values Vd ^* and Vq ^* 23 and a calculation means 24 related to the estimation of the mechanical inertia value.

The calculation means 24 includes a speed command creation unit 24A that supplies a speed command value N ^* to the speed control unit 21, an inertia estimated value calculation unit 24B that calculates an estimated value of mechanical inertia from the torque current command value Iq ^* , The control unit includes a control constant calculation unit 24C that automatically corrects the control constant of the speed control unit 21 based on the mechanical inertia value estimated by the calculation unit 24B.

Next, mechanical inertia value estimation processing (estimated value calculation) will be described. In the inertia value estimation process, an estimated value of inertia is calculated from each torque current command value Iq ^* during acceleration operation and deceleration operation based on the pattern of the speed command N ^* created by the speed command creation unit 24A. FIG. 2 is a relationship diagram between the speed command N ^* pattern created by the speed command creation unit 24A and the torque current command value Iq ^* . In the trial operation for estimating the mechanical inertia value, the acceleration operation from the speed command value N1 (the number of revolutions) to N2 and the deceleration operation from N2 to N1 after the continuous operation of N2 are performed. Further, the acceleration time ΔT _acc and the deceleration time ΔT _{dec at} this time are both set equal to ΔT.

The estimation process is performed by the inertia estimated value calculation unit 24B by integrating the torque current command value Iq ^* and calculating the inertia estimated value based on this integration. Here, as the integrated value of the torque current command value, the integrated value of the torque current Iq ^* period [Delta] T _acc of acceleration operation and ShigumaIq _acc, and ShigumaIq _dec an integrated value of the torque current Iq ^* period [Delta] T _dec of deceleration . The difference between the integrated values ΣIq _acc and ΣIq _dec is twice the acceleration torque τ _acc during the period ΔT. Here, by taking the difference between the acceleration operation and the deceleration operation, it is possible to remove only the influence of the constant load and the rotation speed-dependent load as the load torque other than the acceleration torque, and to estimate only the mechanical inertia value.

τ _acc = (ΣIq _acc −ΣIq _dec ) / 2
τ _acc : acceleration torque during the period of ΔT ΣIq _acc : integrated value of torque current during acceleration ΣIq _dec : integrated value of torque current during deceleration Here, the torque required to accelerate from N1 to N2 during ΔT is τ _Since it is _acc , the mechanical inertia value J at this time can be obtained by the following equation.

J = Kt · τ _acc · 60 / (ΔT · 2π)
Kt: Torque conversion coefficient Thereby, the mechanical inertia can be obtained by the following equation using the integrated values ΣIq _acc and ΣIq _dec of the torque current.

J = Kt · (ΣIq _acc −ΣIq _dec ) · 60 / (2 · ΔT · 2π) (1)
Here, assuming that the mechanical inertia value before estimation is J ₀ , the estimation ratio K with the estimated mechanical inertia value is as follows.

K = J / J ₀ (2)
Then, the control constant calculation unit 24C corrects the control constant of the speed control unit 21 based on the calculated estimated value of mechanical inertia. Here, using the calculated estimated ratio K, the control constants (proportional gain K _sp , integral gain K _si ) of the speed control unit 21 are automatically corrected according to the following equations.

K _sp = K · K _sp0
K _si = K · K _si0
K _sp0 : Proportional gain before automatic correction K _si0 : Integral gain before automatic correction Next, by using the flowchart of FIG. 3, a series of processes for estimating the mechanical inertia value and automatically correcting the control constant of the speed control unit 21 are performed. The flow will be described.

  First, in a trial operation for estimating (tuning) the mechanical inertia value, an acceleration / deceleration time ΔT as an initial value is set in step (S) 101 at the beginning of the first operation. ΔT is calculated by the following equation.

ΔT = J ₀ · (N2−N1) · 2π / (Kt · Iq ^* ₁ · 60) · A (3)
Here, J ₀ is the mechanical inertia value of the previous estimate tentative advance becomes a parameter set from the outside, the approximate value of the system load is connected to the case of the known sets an estimate, estimate If the value is unknown, set the inertia value of the motor alone. Accordingly, a value smaller than the actual inertia value of the system is temporarily set. In addition, since the true value of the inertia of the system is operated without being known, an overshoot may occur in the rotation speed and current of the motor. Even at this time, the torque current command value Iq ^* ₁ in the above equation is The current value is set such that the protection operation does not occur and is not too small (the inertia estimation accuracy does not decrease). Specifically, a value corresponding to the rated current of the power converter is used.

  Furthermore, in the above equation (3), by multiplying the safety factor A (about 20) and setting ΔT to a large value and slowly accelerating / decelerating, even if the overshoot occurs, the current value is suppressed and the motor fails And protection actions are prevented from occurring. Note that the safety factor A is not taken into account in the second and subsequent acceleration / deceleration operations of mechanical inertia estimation.

Next, acceleration operation and deceleration operation are performed using ΔT calculated by the above equation (3). Based on the speed command value N ^* from the speed command generator 24A, the acceleration operation is performed in the time period ΔT from the speed N1 to N2 in S102, and the deceleration operation is performed in the time period ΔT from the speed N2 to N1 in S104. During the acceleration operation period, the torque current is integrated in S103, and is stored in the inertia estimated value calculation unit 24B as an integrated value ΣIq _acc . During the deceleration operation period, the torque current is integrated in S105, and is stored in the inertia estimated value calculation unit 24B as the integrated value ΣIq _dec . As the torque current accumulated at this time, a torque current command value Iq ^* that is an output of the speed control unit 21 is used.

Next, in S106, based on the integrated value of the torque current which has been determined by the S103 and S105, the estimated inertia J ₁ by acceleration and deceleration operation for the first time, the estimated ratio K is obtained as follows.

J ₁ = Kt · (ΣIq _acc −ΣIq _dec ) · 60 / (2 · ΔT · 2π) (4)
_{K = J 1 / J 0 ...} (5)
Subsequently, in S107, it is determined whether to repeat the acceleration / deceleration operation for inertia estimation. Specifically, if the estimated ratio K is in the range of (1-α) to (1 + α), it is determined Yes in S107, and the process proceeds to S113 to stop the acceleration / deceleration operation for inertia estimation and normalize the process. finish. That is, if the estimation ratio K is close to 1 in this determination, it is determined that the estimated value of inertia has converged to be a correct value.

If the estimated ratio K is outside the range of (1-α) to (1 + α), the estimated value of inertia has not converged, and it is determined No in S107, and acceleration / deceleration operation for estimating the inertia value again is performed. Start preparation. In S108 (4) based on the estimated inertia value J ₁ calculated by the equation deceleration time ΔT is calculated anew by the following equation. Here, the safety factor A is not taken into consideration.

ΔT = J ₁ · (N2−N1) · 2π / (Kt · Iq ^* ₁ · 60) (6)
Next, in S109, the estimated ratio K obtained in the previous equation (5) is compared with the specified value B. As a result of the comparison, if larger than the specified value B, the estimated ratio K is forcibly replaced with the specified value B in S110, and the control constant of the speed control is corrected in S111 based on this replaced K (B). Note that if the control constant changes greatly during this correction, the acceleration / deceleration operation may become unstable, so an upper limit value (specified value) B is provided for the estimated ratio K. In the embodiment, the specified value B is set to 2.

  Next, the process proceeds to S112, where the number of acceleration / deceleration operation processes is compared with a predetermined number C, and if it exceeds, the process ends as abnormal. This is to protect the apparatus from an abnormality or runaway of the apparatus when the estimated inertia value does not converge even if it exceeds the predetermined number of times C. If the number of acceleration / deceleration operation processes does not exceed the predetermined number C, the process returns to S102, and another acceleration / deceleration operation for inertia estimation is performed. This acceleration / deceleration operation is performed based on the time ΔT calculated in S106 and the control constant corrected in S111. Then, the steps S102 to S112 are repeated.

Estimation processing of the second inertia, since acceleration and deceleration operation by a control constant and modified acceleration and deceleration time based on the inertia value J ₁ obtained by estimation by first takes place, the inertia value J ₂ is converged Since it is calculated in the direction, the estimation accuracy is improved from the first time. Then, by repeatedly performing this estimation process, the estimation accuracy of the inertia value is improved in an accelerated manner. In this way, it is possible to greatly improve the estimation accuracy of the inertia value for the permanent magnet synchronous motor and the induction motor.

  If the estimated value of inertia converges by repeating the above estimation process several times, it is determined Yes in S107, and the control constant for speed control is corrected to the value for actual operation based on the inertia value converged in S113, and the inertia value The trial run for estimation ends (normal end), and prepares for the actual operation of the motor.

  Further, in order to avoid runaway when the estimated value does not converge, when the number of repetitions is C or more, the process is ended even when the estimation is not converged as abnormal termination.

Here, FIG. 4 and FIG. 5 show an operation example of the present embodiment. FIG. 4 is a relationship diagram of the speed command N ^* (shown by a solid line), the detected speed N (shown by a broken line), and the torque current command value Iq ^{* in} the initial inertia value estimation process. Since the inertia value used for the control constant of the speed control unit is set to a small value of about 1/20 of the actual value for the first estimation process, overshoot is seen in the speed and current command value. FIG. 5 is a relationship diagram between the speed (N ^* , N) and the current command value (Iq ^* ) when the estimated value is converged by the inertia value estimating process. It can be seen that the converged inertia value is as large as about 20 times the initial value shown in FIG. 4 and almost coincides with the actual value, so that overspeed is not seen in the speed and current command values and the control can be performed stably.

It is a block diagram of a power converter of an example of the present invention. It is a relationship diagram of the speed command and torque current command value at the time of acceleration / deceleration operation of the embodiment of the present invention. It is a flowchart of an estimation process operation of the inertia value of the embodiment of the present invention. FIG. 6 is an explanatory diagram of a relationship between a speed command, a detected speed, and a torque current command value in an initial inertia value estimation process according to an embodiment of the present invention. It is a relation explanatory view of the speed command, the detected speed, and the torque current command value in the converged inertia value of the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electric motor, 20 ... Power converter, 30 ... Current detector, 40 ... Speed detector, 21 ... Speed control part, 22 ... Current control part, 23 ... Voltage control part, 24 ... Calculation means, 24A ... Speed command preparation , 24B: Inertia estimated value calculation unit, 24C: Control constant calculation unit.

Claims (9)

A power converter that drives the motor, a speed control unit that outputs a torque current command value according to a deviation between the speed command value and the speed detection value, a current control unit that controls an output current according to the torque current command value, and an actual operation In the power conversion device provided with the arithmetic means for estimating the mechanical inertia value connected to the load by the previous acceleration / deceleration operation and automatically correcting the control constant of the speed control unit,
The calculating means estimates a mechanical inertia value by acceleration / deceleration operation and calculates an next acceleration / deceleration time based on the estimated mechanical inertia value, and based on the calculated acceleration / deceleration time. A speed command generation unit that outputs a speed command value to the speed control unit, and a control constant calculation unit that corrects a control constant of the speed control unit based on the mechanical inertia value estimated above. Power conversion device.   The inertia estimated value calculation unit sets the initial acceleration / deceleration time to be longer considering the safety factor, calculates the subsequent acceleration / deceleration time based on the estimated mechanical inertia value, and the control constant calculation unit calculates the subsequent acceleration / deceleration time. The power conversion device according to claim 1, wherein a control constant of the speed control unit is corrected based on an estimated mechanical inertia value in preparation for a deceleration operation.   The inertia estimated value calculation unit obtains an estimated ratio of the mechanical inertia values estimated in the previous and current acceleration / deceleration operations, and terminates the subsequent estimation when the estimated ratio is within a predetermined range, and is not within the predetermined range 3. The electric power according to claim 1, wherein a mechanical inertia value due to a second acceleration / deceleration operation is estimated, and the control constant calculation unit corrects a control constant of a speed control unit based on the estimation ratio. Conversion device.   The inertia estimated value calculation unit obtains an estimated ratio of the mechanical inertia values estimated in the previous and current acceleration / deceleration operations, and determines that the mechanical inertia value has converged when the estimated ratio is within a predetermined range. The power conversion device according to any one of claims 1 to 3, wherein when the estimation is finished and the mechanical inertia value is not within a predetermined range, the acceleration / deceleration operation is repeated until the mechanical inertia value converges to estimate the mechanical inertia value.   The inertia estimated value calculation unit obtains an estimated ratio of mechanical inertia values estimated in the previous and current acceleration / deceleration operations, and when the estimated ratio exceeds a specified value, replaces the estimated ratio with a specified value, and the control constant calculating unit The power conversion device according to claim 1, wherein the control constant of the speed control unit is corrected based on the estimated ratio replaced with a specified value.   The power conversion apparatus according to claim 1, wherein the inertia estimated value calculation unit ends the operation when the repetition of the acceleration / deceleration operation reaches a predetermined number of times.   The inertia estimated value calculation unit integrates the torque current during acceleration and deceleration during acceleration / deceleration operation, and adds the motor and mechanical inertia based on the difference between the accumulated value of the torque current during acceleration and the accumulated value of the torque current during deceleration. The power conversion according to claim 1, wherein an acceleration torque used for deceleration is estimated, and a mechanical inertia value is estimated from the acceleration torque integrated value and an acceleration / deceleration time in acceleration / deceleration operation. apparatus. A power converter that drives the motor, a speed control unit that outputs a torque current command value according to a deviation between the speed command value and the speed detection value, a current control unit that controls an output current according to the torque current command value, and an actual operation In the power conversion device including a calculation means for estimating the mechanical inertia value connected to the load by the previous acceleration / deceleration operation and correcting the control constant of the speed control unit,
The calculating means repeatedly calculates an acceleration / deceleration time for the next acceleration / deceleration time until the estimated mechanical inertia value converges, and sends a speed command value to the speed control unit based on the calculated acceleration / deceleration time. A power converter comprising: a speed command generating unit for outputting; and a control constant calculating unit for correcting a control constant of the speed control unit based on a mechanical inertia value estimated by acceleration / deceleration operation.   The inertia estimated value calculation unit integrates the torque current during acceleration and deceleration during acceleration / deceleration operation, and adds the motor and mechanical inertia based on the difference between the accumulated value of the torque current during acceleration and the accumulated value of the torque current during deceleration. The power conversion apparatus according to claim 8, wherein an acceleration torque used for deceleration is estimated, and a mechanical inertia value is estimated from the acceleration torque integrated value and an acceleration / deceleration time in the acceleration / deceleration operation.

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