JP4066567B2 - Vector control device for electric motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor vector control apparatus, and is particularly useful when applied to vector control of an induction motor.
[0002]
[Prior art]
A vector control system is known as a high-performance speed control system for induction motors. The vector control system having a speed sensor is capable of high-accuracy speed control and high-response torque control, and is therefore used as a rotary drive device for equipment that requires machining accuracy. However, the place where the induction motor is installed is often a poor environment with a lot of oil and moisture, and the speed sensor may fail or the signal line for speed detection may be broken. In this way, if the speed sensor breaks down and the signal line is disconnected, the vector control steeply decelerates to zero speed, which adversely affects processed products and machines that are driven to rotate by the induction motor. End up. In particular, when the quality of a processed product changes if the operation is not continued as in a mixer, it may be desired to continue the operation even after switching from vector control to V / f control.
[0003]
[Problems to be solved by the invention]
In vector control, there is known a method of switching to V / f control and continuing operation when it is desirable to continue operation without stopping even if an abnormality occurs in the speed sensor. In this operation method, considering the continuity of the output voltage at the time of switching, the voltage is output with the same phase and the same amplitude as the last output voltage vector during vector control, and then changes to the V / f pattern at a certain rate of change. The method to make it take is taken.
[0004]
As described above, when the vector control and the V / f control are switched, the voltage vector and the current vector are in different phases and amplitudes even in the steady state due to the difference between the current feedback control and the voltage open loop control. For this reason, consideration must be given so that both the voltage vector and the current vector can be continuously switched during switching. However, in particular, when returning from V / f control to vector control, torque ripple is generated, and when switching is performed during a transition, a protection function such as overcurrent may be activated. .
[0005]
In view of the above prior art, in the vector control having a speed sensor, the present invention can continue the operation of the motor satisfactorily even when a failure occurs in the speed detection system, such as a failure of the speed sensor, and the speed An object of the present invention is to provide a vector control device for an electric motor that is capable of satisfactorily switching to an operation mode based on the original vector control when the detection system is restored.
[0006]
The configuration of the present invention that achieves the above object is characterized by the following points.
[0007]
1) A vector based on the detected speed value by selecting one of the speed detection value obtained by processing the measured value of the motor speed and the speed estimated value obtained as an output signal of the same-dimensional magnetic flux observer and the speed estimation mechanism by the selection means. In the motor vector control device configured to control the motor by control or sensorless vector control based on the estimated speed value,
When an abnormality in the motor speed based on the actually measured value is detected, the selection means is switched, the speed estimated value is selected to select sensorless vector control, and the speed detection based on the actually measured value returns to normal. In such a case, the selection means is switched again, and the sensorless vector control is configured to return to the vector control based on the actual measurement value .
In addition, the maximum speed change amount that can be changed in the calculation cycle time is obtained from the current torque limit value and the load inertia model value, and based on that value or the maximum speed change amount obtained by multiplying the value by a coefficient, the maximum speed change amount is exceeded. When the speed is changed, the motor speed based on the measured value is regarded as abnormal,
When the error between the speed estimation value and the speed detection value falls within a predetermined range, the actual measurement value is regarded as having returned to a normal state .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 is a block diagram showing a control device according to an embodiment of the present invention. As shown in the figure, the control device according to the present embodiment includes a vector control system based on a speed detection value that is an output signal of the speed detection unit 1 based on an actual measurement value, an output signal of the same-dimensional magnetic flux observer and the speed estimation mechanism 2. Substantially has two control systems, a sensorless vector control system based on the estimated speed value. The former detects the actual rotational speed of the induction motor 1 based on the output signal of the speed sensor 4. Here, the speed sensor 4 is connected to the rotating shaft of the induction motor 3 to detect the speed of the induction motor 3. The latter calculates a speed estimated value based on the current supplied to the induction motor 3 and the voltage applied to the PWM inverter 7. Here, the current supplied to the induction motor 3 is detected by the current detector 5, and the voltage applied to the PWM inverter 7 is detected by the output voltage detector 6.
[0013]
The selection switch 8 selects either the speed detection value or the speed estimation value and uses them as input signals to the magnetic flux command unit 9 and the subtracter 10. The selection switch 8 is switched by a speed selection signal from the speed detector 1. Here, the speed detection unit 1 includes a speed detection abnormality determination unit. When a speed detection abnormality is detected, the speed detection unit 1 switches the selection switch 8 so as to select a speed estimation value, and a speed detection return determination unit. When the speed detection returns to normal, the selection switch 8 is switched to select the speed detection value again. That is, it has a function of switching from vector control to sensorless vector control when speed detection is abnormal, and has a function of returning from sensorless vector control to vector control when the speed detection function is restored.
[0014]
As described above, the speed detection unit 1 according to the present embodiment includes the speed detection abnormality determination unit. As a specific example of the speed detection abnormality determination unit, the following embodiments can be considered.
[0015]
(1) Set the maximum speed change amount for speed detection abnormality judgment, and if the speed changes exceeding the maximum speed change amount within the calculation cycle time, it is regarded as a speed detection abnormality, and from vector control to sensorless vector control Switch.
[0016]
(2) The maximum speed change amount that can be changed in the calculation cycle time is obtained from the current torque limit value and the load inertia model value, and the maximum speed change amount is calculated based on the value or the maximum speed change amount obtained by multiplying the value by a predetermined coefficient. When the speed changes more than the change amount, it is regarded as speed detection abnormality, and the vector control is switched to the sensorless vector control.
[0017]
Further, as a specific example of the speed detection return determination unit of the speed detection unit 1, the following embodiments can be considered. That is, when the error between the speed estimation value and the speed detection value falls within a certain range, it is considered that the speed detection function has been restored, and the sensorless vector control is returned to the vector control.
[0018]
In this embodiment, the speed information of the induction motor 3 is selected as either a speed detection value that is an actual measurement value or a speed estimation value that is an estimation value, and the processing system for the speed detection value or the speed estimation value is configured in common. is there. That is, it has substantially two control systems, a vector control system and a sensorless vector control system. The configuration of the common part in this case is as follows.
[0019]
The magnetic flux command unit 9 supplies a magnetic flux command determined in advance based on the speed detection value or the speed estimation value to the magnetic flux / current conversion unit 10. As a result, the magnetic flux command is converted into a magnetic flux current command. On the other hand, a speed command supplied from a speed command unit (not shown) takes a deviation from a speed detection value or a speed estimation value by a subtractor 11, and this deviation is transmitted via a speed adjustment unit 13 to a torque / current conversion unit 13. To be supplied. As a result, the speed (torque) command is converted into a torque current command. The magnetic flux current command and the torque current command take a deviation from the current detection value which is the output signal of the current detection unit 5 by the subtractors 14 and 15, and based on each deviation, the d-axis voltage command and q Obtain the shaft voltage command. The two-phase / three-phase conversion unit 18 performs a predetermined calculation on the basis of the d-axis voltage command and the q-axis voltage command to convert it into a three-phase voltage, and applies it to the PWM inverter 7 as an input voltage of the PWM inverter 7. The PWM inverter 7 controls the power supplied so that the induction motor 3 rotates at a predetermined speed.
[0020]
The parts other than the speed detection unit 1, the same-dimensional magnetic flux observer, and the speed estimation mechanism 2 inherent to the vector control and the sensorless vector control may be any of a conventionally known vector control apparatus and sensorless vector control apparatus.
[0021]
【The invention's effect】
As described in detail in conjunction with the embodiments above, according to the present invention, vector control and sensorless vector control can be used in common for portions other than the speed detection unit or the same-dimensional magnetic flux observer and the speed estimation mechanism, Moreover, since the handling of the voltage vector and the current vector is the same, continuous switching is possible. In addition, since it can be switched even during a transition, it can cope with speed detection abnormalities during acceleration, deceleration, load fluctuation, etc., and not only greatly improves the reliability, but also sensorless vector control over V / f control Because of its high speed control performance, it is possible to minimize deterioration of control performance when speed detection is abnormal.
[0022]
Furthermore, even if the speed detecting means fails, if the failure can be repaired during operation, for example, disconnection, it is possible to repair it during operation and then return to vector control.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a control device according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Speed detection part 2 Same dimension magnetic flux observer and speed estimation mechanism 3 Induction motor 4 Speed sensor 7 PWM inverter 8 Selection switch

Claims (1)

Vector control based on the speed detection value by selecting either the speed detection value obtained by processing the actual value of the motor speed and the speed estimation value obtained as the output signal of the same-dimensional magnetic flux observer and the speed estimation mechanism by the selection means or In the motor vector control device configured to control the motor by sensorless vector control based on the estimated speed value,
When an abnormality in the motor speed based on the actually measured value is detected, the selection means is switched, the speed estimated value is selected to select sensorless vector control, and the speed detection based on the actually measured value returns to normal. In such a case, the selection means is switched again, and the sensorless vector control is configured to return to the vector control based on the actual measurement value .
In addition, the maximum speed change amount that can be changed in the calculation cycle time is obtained from the current torque limit value and the load inertia model value, and based on that value or the maximum speed change amount obtained by multiplying the value by a coefficient, the maximum speed change amount is exceeded. When the speed is changed, the motor speed based on the measured value is regarded as abnormal,
A vector control apparatus for an electric motor , wherein when the error between the estimated speed value and the detected speed value falls within a predetermined range, the measured value is regarded as having returned to a normal state .

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