JPS63287384A - Induction machine controller - Google Patents

Abstract

PURPOSE:To prevent resonance phenomena in a power system by skipping a specific frequency at the time of regulating the operating frequency of a secondary chopper according to the rotational speed of an apparatus. CONSTITUTION:A current command signal i is obtained in a speed regulator 12 by comparison of a detection signal through a speed detector 10 with a speed command signal through a speed command circuit 11. The deviation vd2 of said current command signal i from a current detection signal through a current detector 13 is compared with an output signal vA from a triangular wave generator 16 to give the ON-OFF signal of a secondary chopper 3. In this case, the output frequency of said triangular wave generator 16 is controlled by a frequency control circuit 17 according to said speed command and being set so as to skip a specific frequency. In this manner, the operating frequency of said secondary chopper 3 is also regulated so as to skip a specific frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an induction machine capable of secondary excitation control, and particularly to a control device suitable for variable speed control of pumps, fans, and the like.

[Conventional technology]

Conventional devices connect a forward converter (AC-DC converter) to the secondary side of a single-winding linear induction machine, as described in JP-A-60-28782 and JP-A-60-82,082. A chopper for adjusting the secondary current of the induction machine is connected to the forward converter, and the rectified output of the forward converter is periodically short-circuited by the chopper to adjust the secondary current.

A method for controlling the speed of an electric motor is described. Furthermore, in these conventional examples, he mentioned the problem that sufficient secondary current does not flow at high speeds, and as a means to prevent this, the chopper frequency of the secondary chopper is changed according to the slip frequency of the electric motor, thereby increasing the rotation speed. The company claims that this will improve control performance by allowing sufficient secondary current to flow throughout the entire range. However, in these devices, no consideration was given to the resonance phenomenon with the power supply system.

[Problem that the invention seeks to solve]

The above conventional technology does not consider resonance with the power supply system, and when the chopper frequency changes continuously, the frequency becomes a certain value.

Due to the starting harmonics flowing out from the primary of the induction machine, excessive harmonic current flows due to resonance in the power supply system.

There was a risk of damage to equipment connected to the grid.

An object of the present invention is to provide a method for reducing excessive harmonic current caused by this resonance phenomenon.

[Means for solving the problem] The above object is to provide an induction machine capable of secondary excitation, a forward converter for converting the secondary voltage of the induction machine into direct current, and a converter for controlling the secondary current in the forward converter. In an apparatus comprising a secondary chopper connected, a series circuit of a capacitor and a diode connected in parallel with the secondary chopper, and an inverse converter connected to convert the power of the capacitor into alternating current and regenerate it to the power source. , is achieved by skipping certain frequencies when adjusting the operating frequency of the secondary chopper according to the rotation speed.

[Effect]

The deviation value vd21 between the current command signal i output from the speed regulator by comparing the command signal from the speed command circuit and the detection signal from the speed detector and the current detection signal from the current detector is determined by the triangular wave generator. It outputs an on/off signal for the secondary chopper. At this time, the output frequency of the triangular wave generator is controlled by the frequency control circuit.
It is controlled according to the speed command and is set to skip a specific frequency.

As a result, the operating frequency of the secondary chopper is also adjusted to skip a specific frequency, so the harmonic components included in the primary current of the induction machine do not include specific frequency components that may cause resonance with the power supply system. You can avoid it.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
In the figure, 1 is a wound induction motor (a secondary chopper that controls the secondary current of IM'l by on/off operation);
4 is a reverse current blocking diode, 5 is a capacitor that stores the current that flows in when the secondary chopper is off and smooths the DC voltage, and 6 is a regenerative inverter that maintains the voltage of the capacitor at a predetermined value. This is a regenerative chopper that controls the current. 3 and 6 are self-extinguishing elements, and transistors or GTOs are used. 7 is a freewheeling diode,
8 is a thyristor inverse converter (regenerative inverter) for regenerating the secondary power of the IMI to an AC power source, and 9 is a transformer.

Next, the control circuit section will be explained. 10 is a speed generator directly connected to the IMI, 11 is a speed command circuit, and 12 is a system that amplifies the deviation between the output signal of the speed detector 10 and the speed command signal to generate a command signal for the output current of the forward converter 2. It is a speed regulator that outputs. 13 is a current detector for detecting the output current of forward converter 2; 14 compares the current command signal from speed regulator 12 with the current detection signal, and generates a deviation signal vd2*
A comparator 15 outputs the deviation signal ν of the comparator 14.
d2 umbrella and a comparator that compares the output signal 9A of the triangular wave generator 16 and outputs an on/off control signal for the secondary chopper 3; 17 is a frequency control circuit that controls the generated frequency of the triangular wave generator 16; Although it is configured to output an output signal in response to a speed command, it is set in advance to skip only a certain frequency component. 1
8 is an amplifier for supplying on/off control signals to the secondary chopper. Control circuits 19 to 23 control the voltage of the capacitor 5 to be constant. 19 is a voltage command circuit; 20 is a voltage detector; 21 is a voltage regulator that amplifies the deviation between the signal of the voltage detector 20 and its command signal and outputs a command signal to the input current of the inverter 8; 22 is a current detector of the inverter 8;

23 is a comparator with a hysteresis characteristic that outputs an on/off control signal for the regenerative chopper 6, and 24 is a base amplifier for driving the regenerative chopper 6 with the signal. 2
5 is a control circuit for controlling the firing of the inverter 8 at a constant firing phase.

The basic operation of this embodiment is as follows. The output signal i of the speed regulator 12, the current detection signal id1, and the deviation νd2
The secondary chopper 3 is turned on and off depending on the deviation between * and the output of the triangular wave generator 16 (No. Control the torque.

Perform speed control. By the way, during the period when the secondary chopper is off,
The DC current is charged to the capacitor 5 via the diode 4. At this time, the secondary power of the IMI is converted to DC power and stored in the capacitor 5. Next, the regenerative chopper 6 is turned on and off so that the voltage of the capacitor 5 becomes constant. When the regenerative chopper 6 is turned on, current flows from the capacitor 5 to the inverter 8, so the charging/discharging current of the capacitor 5 is balanced and the voltage is constant.0 The output voltage of the regenerative chopper 6 is converted to alternating current by the inverter 8. be done. In this way, the secondary power of the IMI is regenerated into an AC power source. Here, I
Although the speed of the MI can be arbitrarily controlled by the command value of the speed command circuit 11 and the voltage of the capacitor 5 can be controlled by the voltage command value of the voltage command circuit 19, in the present invention, the operating frequency of the secondary chopper can be controlled as described above. When changing the frequency according to the speed according to the command of the frequency control circuit 17, the setting of the circuit
I am trying to skip only certain frequencies.

The primary current of the IM contains harmonic components of the chopper frequency, but by skipping a specific frequency in this way, harmonics that would cause a resonance phenomenon in the power supply system are not included, and therefore excessive harmonics due to resonance are avoided. Current can be prevented.

In addition, as another embodiment of the present invention, the chopper frequency is not only changed depending on the rotation speed.

It may be changed depending on the secondary frequency of IM. Because I
The secondary frequency (slip frequency) f2 of M is fz=fx
fr --(1) Here, fl
This is because knee-order frequency (constant) fr: rotational frequency and is related to rotational speed.

Here, the secondary frequency of the IM can be detected by detecting the frequency of the secondary current. For example, the secondary current is passed through a filter and converted into a sine wave signal, then converted into a pulse signal by a comparator and counted for seven seconds, or conversely, the period of the pulse signal is measured (the clock signal is This is possible by counting each time.

〔Effect of the invention〕

As described above, according to the present invention, resonance phenomena in the power supply system can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of an induction machine control device according to the present invention. 1...Induction machine, 2...Forward converter, 3...Secondary chopper.

Claims (1)

[Claims] 1. An induction machine capable of secondary excitation, a forward converter that converts the secondary voltage of the induction machine into DC, and a secondary that shorts the output of the forward converter directly or through a DC reactor during ON operation. A control device connected to a chopper is characterized by having a chopper control circuit that prohibits a specific frequency when changing the on/off frequency of the secondary chopper in accordance with the speed of the motor. A control device for an induction machine.