JPS60219997A - Controlling method and device for suppressing vibration of ac motor - Google Patents

Abstract

PURPOSE:To suppress the vibration of an AC motor by discriminating power drive or regenerative state from the polarity of a DC current, and correcting the basis frequency command of an inverter so as to cancel this state on the basis of the discrimination signal. CONSTITUTION:The input current ID of an inverter is detected by a current transformer 13, and the power drive or a regenerative state of an AC motor is discriminated from the polarity of a current by a current polarity discriminator 100. The basic frequency f1 of the inverter is corrected to become the power drive state if a regenerative mode is presented by a frequency correcting circuit 20, and the correction signal is output to an adder 300 to correct to become the regenerative state when the power drive mode is, on the contrary, presented, and added with a frequency set signal fR.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to vibration suppression control when an induction motor is driven at variable speed by performing constant v/f control with an AC inverter driven by an inverter [Background of the Invention] ] When an induction motor is driven with a constant v/f using a PWM inverter, the moment of inertia is relatively small in a frequency range lower than the rated frequency, for example, about 10 to 30 Hz, and the motor can be driven from a no-load state to a light load of about 10 to 20 inches. Under certain load conditions, instability phenomena occur that cause abnormal vibrations.

For example, a device disclosed in Japanese Patent Publication No. 53-27807 is known as an abnormal vibration suppression control device for an electric motor when this unstable phenomenon occurs. This detects an amount proportional to the power, introduces it into a bandpass filter, and uses the signal obtained from the output of this filter as a stabilizing signal to suppress vibrations, which is added to the frequency setting to prevent vibrations. This is how it was done.

However, even with this device, it is difficult to achieve accurate stabilization depending on the type of motor, such as the number of pole pairs, secondary resistance, etc., and it often occurs that one motor is stable but another motor is not. . It has been experimentally confirmed that this tendency becomes particularly noticeable as the number of poles becomes smaller.

In addition, the above-mentioned vibration suppression device outputs an unnecessary stabilization signal even when the load suddenly changes, and the set frequency is corrected, so the speed does not fluctuate. [Objective of the Invention] The present invention solves the above-mentioned problem and provides vibration suppression for an AC motor that can be sufficiently stabilized regardless of the type of motor and the load condition. The present invention provides a control method and device thereof.

[Summary of the invention]

As a result of many experiments, the inventors of the present invention found that when the electric motor is unstable due to abnormal vibrations, vibrations are generated by alternating between the magistrate state and the regeneration state. We have learned that it is best to take advantage of this vibration to create a regenerative or left-handed state. Furthermore, these modes have been accurately grasped as the polarity of the direct current input to the converter, and the scales have also been identified, leading to the present invention.

The present invention determines whether the AC motor is in a dedicated or regenerative state based on the polarity of a DC current input to a pulse width modulation inverter that drives the AC motor based on a basic frequency command, and based on this determination signal, The vibration of the AC motor is suppressed by correcting the basic frequency command of the inverter so as to cancel out the state.

[Embodiments of the invention]

Examples of the present invention will be described in detail below. FIG. 1 shows the system configuration of the vibration suppression control device of the present invention. This system is comprised of a smoothing capacitor 0 connected to a DC power source, a PWM inverter 1 connected to the smoothing capacitor 0 that converts the DC power source into a variable frequency alternating current power source, and an induction motor 12 driven by this power source. In this system, the inverter frequency f1 is the v/f converter 1
8 into a pulse train, and the PWM signal forming circuit 19
A PWM signal corresponding to fl is generated.

The PWM inverter 1 operates based on the above PWM signal to drive the induction machine 12 at variable speed.

The vibration suppression control device for an AC motor according to the present invention includes frequency correction circuits 200, . 200 and a frequency setting signal (fR). moreover,
The above-mentioned circuits 100 and 200 are circuits of the present invention, and are each comprised of an ID negative side detection circuit 14, a monostable circuit 15, an integrator 16, and a gain converter 17. Next, the operation of the vibration suppression control circuit described above will be explained using the time chart shown in FIG. 2.

FIG. 2 shows the operation in the unstable region ((A) in FIG. 2) and the operation in the stable region ((B) in FIG. 2). In the operating state in the unstable region, the input inverter input current In is in a state in which the exclusive current (1) and the regenerative current (IB) are alternately repeated and sway between positive and negative directions. Therefore, ID is detected through the current transformer 13, and from this current Io
The negative side discrimination circuit 14 selects only the regenerative current In. In the section where Is is flowing, a logic signal (), level (I level), indicated by a in the figure, is output. This logic signal a is input to the monostable circuit 15. This monostable circuit 15 is configured to have a retrigger function, and all signals that enter the time constant (1,) of the monostable circuit are held as non-repetitive logic signals. Time constant [1 is the pulse interval t of signal a
6 (this value corresponds to the switching frequency of the PWM inverter), corresponding to the condition t, <t, 21. may be set in advance so as to satisfy. In this case, (
When the signal a shown in A) is input, the first rise of the high level of the signal a triggers the output signal of the monostable circuit 15 to change from low level (α) to irregular level (β), As long as the signal a is input, the state of high level (β) is maintained, and after the time 1.1□ after the signal a is input, it transitions to < /- (a), 6 degrees. Therefore, by adopting such a configuration, in a stable cine state, the low level signal corresponds precisely to the section where the regenerative current IB is flowing, and the low level signal corresponds to the section where the ≠ row current I is flowing. This output allows you to distinguish between force regeneration mode and dedicated mode.

The fundamental frequency fl of the inverter is corrected to bring it into a regenerative state when it is in the power mode. This is accomplished by using the signal S to operate integrator 16 as follows.

That is, the frequency setting signal f is integrated from the rising point of the signal f.
For n, the adder 300 outputs its value so that it is positive (negative), and the integrator 1 is controlled to be discharged at the falling edge of the above signal An integrator 2 is provided which integrates from the bottom 9 points and operates in the completely opposite manner to the case of the start-up described above. Since it is configured so that the current mode is on the positive side, the transition to this mode will be stopped.

Note that the integration and discharge time constants of this integrator 16 must be approximately several ms, and must be operated at high speed.

The amount to be further corrected is determined by the next gain conversion circuit 17. That is, the signal q is converted by the circuit 17 into a very small value Δf' that is within the range of the slip frequency, the amount required for correction.

The signal d output from the circuit 17 is added to the frequency setting signal fa by an adder 300. The signal d is added as a stabilization control signal to the frequency command f1 of the inverter.

Above, we have mainly explained the operation of the vibration suppression control circuit in an unstable case, but in a stable case, as shown in Fig. 2 (B), in a no-load state, the IA,
Since the signals af′i and II flow almost alternately, a pulse train with the Hals interval [,] is created continuously, and the monostable circuit 1
5 continues to be retriggered by this pulse, and the output signal of the circuit 15 remains at a high level. Therefore, one state of the integrator 16 (the second
In (B) of the figure, the state remains on the positive side), so the correction of the fundamental frequency is no longer automatically performed.

Note that (B) in Fig. 2 mainly shows the no-load state, but when a load is applied and the state becomes stable, IA>IIC.
At the time of regeneration, the output of the integrator 16 is biased to the state of IAgh) and is fixed to one side as in the above case, so the correction is automatically stopped.

In this way, the vibration suppression control works effectively only in unstable conditions, so stable drive characteristics of the induction motor can be obtained regardless of the load condition, and a highly reliable control system can be realized.

Next, it is equipped with a stabilizing signal automatic compensation circuit that can automatically correct the output limiter of the gain conversion circuit 17 to ensure stable drive at all times even when the capacity of the motor changes or the operating frequency changes. An example will be described below.

FIG. 3 shows its configuration. In this embodiment, in addition to the above-described embodiment shown in FIG. a stabilization control compensation circuit 21 connected to the output of this circuit and controlling an upper and lower limiter that suppresses the output value of the circuit 17 within a predetermined range based on the signal e; A sample and hold circuit 22 samples and holds the signal g according to the vibration suppression command signal e, and a limiter forming circuit 23 determines the upper and lower limiter values i, +'- of the gain converter 17 based on the output value of the circuit 22. It is equipped with a stabilizing signal automatic compensation circuit consisting of.

The output signal of the monostable circuit is the stabilization command signal forming circuit 20.
A pulse f having a pulse width of Δt is generated in synchronization with the rising edge of the signal S. The noise that enters the signal a force, the sudden ≠ line during acceleration/deceleration operation, and the signal generated by the regeneration mode change are not the original vibration suppression control signals, so the signal f, which has a width of Δt, was removed. Vibration suppression control for signal C.

It is used as a command signal. Accordingly, the signal e described above is used as a control signal for the stabilization control compensation circuit 21, which indicates that a state in which high level and low level signals are alternately repeated is an unstable state. Further, from the circuit 20, a sample hold circuit 22 which will be described later, and a stabilization control compensation circuit 21 which operates based on the vibration suppression command signal e, perform a predetermined operation when a signal e having a high level (corresponding to the shaded area) enters the circuit 21. The discharge starts from the falling time point A and reaches the zero level. On the other hand, while the signal e is at a high level, the sample and hold circuit 22 operates to take in the value of the signal g as is and hold the point A where the signal e changes from a high level to a low level. Then, just before entering the stabilization control compensation operation indicated by the diagonal line of the resetting signal e generated from the rising point B of the signal representing the regeneration mode that appears next, the signal R is returned to zero, and the stabilization control system is activated. This is to ensure that a signal having a magnitude that ensures a stable state is output from the gain conversion circuit 17 as the stabilization signal d during the period of time.

FIG. 4 shows the transition of the operating waveforms of each part from an unstable state to a stable state. First, in an unstable state, the regenerative current II flows, and the signals a1 and b as explained in FIG.
It is output from the monostable circuit 15. As the state transitions to a stable state, the period of the regenerative current ■1 becomes shorter, so the low level section of the signal gradually narrows from tl to 16, and finally that section disappears and becomes a high level logic signal. .

The function of the stabilization signal automatic compensation circuit in this embodiment is as follows.
This is indicated using an arrow in the figure. The series of operations described above are performed while the signal C alternately repeats high and low levels.

As a result, the signal shown in FIG. 4 is obtained from the sample and hold circuit 22. Based on this signal, the limiter forming circuit 23 creates upper and lower limiters 1. , i-. The stable signal d output from the gain conversion circuit 17 operates in conjunction with the limiters i, . . . 1-, and performs the operation shown in FIG. In this case, in order to perform such an operation, it is necessary to increase the gain of the integrator 16 so that the limiter compensation works effectively.

The time chart in FIG. 4 shows several cycles of the stability control compensation operation in order to make it easier to understand the operation of the vibration suppression control circuit according to the embodiment of the present invention. However, if the vibration suppression control circuit is operating ideally, the unstable state changes very quickly to the stable state in approximately one cycle of the signal e. Therefore, it is necessary to determine the constants of the stable control compensation circuit 21 in order to achieve practical stability compensation at high speed.

In this embodiment, the frequency is corrected and the amount of correction is automatically corrected, so even if the motor operates at high speed, it can always operate at high speed, and the range of application is greatly expanded. Become.

〔Effect of the invention〕

According to the present invention, vibrations of an AC motor can be suppressed in a sufficiently stable manner regardless of the type of motor and the state of the load.

[Brief explanation of drawings]

FIG. 1 is a basic configuration of the vibration suppression control circuit of the present invention. FIG. 2 is a time chart explaining the operation of the vibration suppression control circuit of FIG. 1. FIG. 3 is a diagram showing another application example of the present invention. FIG. 4 shows time charts explaining the operation of FIG. 3, respectively. 10... Smoothing capacitor, 11... PWM inverter, 12... Induction motor, 13... Current transformer, 14...
...Negative side discrimination circuit for inverter input current (ID), 15
... Monostable circuit, 16... Integrator, 17... Gain conversion circuit, 18... V/F converter, 19... PWM
Signal forming circuit, 20... Stabilization command signal forming circuit, 2
DESCRIPTION OF SYMBOLS 1... Stabilization control compensation circuit, 22... Sample hold circuit, 23... Upper and lower limiter formation circuit. Agent Akio Takahashi, Patent Attorney ¥31 Day 00 2nd (F3) A' , □ Continued from page 1 @ Inventor Ikuo Okajima Xi "Ichihigashi" Shino Factory

Claims (1)

[Scope of Claims] 1. In a pulse width modulation inverter that drives an AC motor based on a fundamental frequency command, the misalignment or regenerative state of the AC motor power is determined from the polarity of the DC current input to the inverter; An alternating current that corrects the fundamental frequency command of the impark to offset this state based on the discrimination signal! Motivation vibration suppression control method. In claim 1, the AC motor is characterized in that the dedicated or regenerative state is determined based on the length of time that the polarity of the DC current lasts on one side rather than the period of the pulse width modulation signal. vibration suppression control method. 3. In a pulse width modulation inverter that drives an AC motor based on a basic frequency command, a current polarity discrimination circuit that discriminates the polarity of the DC current input to the inverter, and a discrimination signal from the current polarity discrimination circuit. and a frequency correction circuit that generates a stabilizing signal that corrects the basic frequency command of the frequency setting circuit of the inverter, the frequency of the inverter is set so as to cancel the change when the polarity of the input DC current of the inverter changes. A vibration suppression control device for an AC motor that applies a stabilizing signal to the circuit. 4. In claim 3, the current polarity determining circuit includes a negative side determining circuit that detects the conduction period of either the forward current or the regenerative current from the direction of the input DC current of the inverter; It consists of a monostable circuit with a retrigger function that holds the output signal of the side discrimination circuit for a predetermined period of time,
The frequency correction circuit includes an integrator and a gain converter that adjusts the output value of the integrator to a predetermined value. A positive stabilizing signal is added to the basic frequency command in synchronization with the rise of the output signal of the monostable circuit, and a negative stabilization signal is added in synchronization with the fall of the output signal of the monostable circuit on the negative side. This is a discrimination circuit.A vibration suppression control device for an AC motor that outputs a stabilizing signal with the opposite polarity to the above stabilizing signal when detecting the period of current flow. 5. In a pulse width modulation inverter that drives an AC motor based on a basic frequency command, a current polarity discrimination circuit that discriminates the polarity of the DC current input to the inverter, and a current polarity discrimination circuit that discriminates the polarity of the DC current input to the inverter, based on a discrimination signal from the current polarity discrimination circuit. Generating a stabilizing signal to correct a basic frequency command of the frequency setting circuit of the inverter; Applying a stabilizing signal to the frequency setting circuit of the inverter to cancel the change when the polarity of the input DC current of the inverter changes; A vibration suppression control device for an AC motor.