JPS62210878A - Control unit of induction machine - Google Patents

Abstract

PURPOSE:To dispense with a capacitor voltage detector, to improve the serviceability and to miniaturize the unit, by estimating a capacitor voltage from the conducting ratio of a secondary chopper. CONSTITUTION:A non-conducting ratio computing element 22 makes a phase inversion of signals from a comparator 17 and takes out signals related to the non-conducting ratio the the operation of their average value. On the other hand, a sliding computing element 21 using speed detecting signals from a speed detector 10 operates the slide of an induction machine. By dividing the output signals of the sliding computing element 21 and the non-conducting ratio computing element 22 with a divider 23, a capacitor voltage is operated and detected. The conduction of a regenerating chopper 6 is then controlled so that the operational value will agree with a predetermined value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a speed control bag for a secondary excitation capable induction machine, and particularly to control of an induction machine suitable for driving loads such as pumps and fans. Regarding equipment.

[Conventional technology]

A conventional device is a diode rectifier on the secondary side of a wound induction machine and a secondary chopper connected to its output, as described in Japanese Patent Publication No. 56-25879.

The off-state operation was used to adjust the secondary current of the wound induction machine and control the torque. Recently, in order to remove the DC reactor from the main circuit, it has been considered to have a series circuit of a diode and a capacitor in parallel with the secondary chopper, with a regenerative chopper installed between the capacitor and the regenerative inverter. There is. At this time, the capacitor voltage is detected and the regenerative chopper is turned on so that the voltage value remains constant.

An insulated detector is used to detect the capacitor voltage to control the off state.

[Problem that the invention seeks to solve]

However, when the DC voltage becomes high, a voltage detector with high dielectric strength must be used, which is expensive. Furthermore, since the detector handles high voltage, it must be installed away from other control circuits, posing the problem of complicating the device. Furthermore, there were also problems with the reliability of the voltage detector or its peripheral equipment, such as the problem of insulation deterioration.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an induction machine control device that can omit a capacitor voltage detector.

[Means for solving problems]

The above purpose is to calculate the slip from the rotational speed of the induction machine, that is, a signal proportional to the secondary voltage, and further estimate the capacitor voltage from that signal and the conduction ratio of the secondary chopper, so that the calculated value becomes a predetermined value. This is achieved by controlling the conduction of the regenerative chopper.

(Function) That is, the slippage of the induction machine is expressed by the following equation, and can be determined from the rotation speed.

Here, No = synchronous speed, N: actual speed The slip S of the induction machine is proportional to the secondary voltage, and the DC output voltage of the forward converter (
average value) is proportional to this. On the other hand, the input voltage (instantaneous value) of the secondary chopper is:

It is zero when the secondary chopper is on and equal to the capacitor voltage when it is off. At this time, since the average value of the input voltage of the secondary chopper and the average value of the DC output of the forward converter are balanced, the voltage of the capacitor is expressed by the following equation.

T T where, Ec: capacitor voltage, Ezo: induction machine secondary voltage at s=1, T: on/off period of secondary chopper,
TON: conduction ratio, TOFF: non-conduction ratio.

In other words, the secondary voltage 5Ezo of the induction machine and the conduction ratio TON
/T, the capacitor voltage can be determined according to equations (1) and (2).

By controlling the regenerative chopper using this voltage,
Voltage detector can be omitted.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a load 30 such as a pump or a fan is mechanically directly connected to a wound induction machine 1, and a rotation speed detector 1 is further connected to the wound induction machine 1.
0 is installed. A diode rectifier 2 is provided on the secondary side of the wound induction machine 1, and a self-extinguishing element (transistor, GTO) is provided at its output.

A secondary chopper 3 using a MOS-FET (MOS-FET, etc.), a backflow blocking diode 4, a capacitor 5, a regenerative chopper 6 using a self-extinguishing element, a freewheeling diode 7, and a regenerative inverter 8 using a thyristor are connected. Further, the output of the regenerative inverter 8 is connected to an AC power system via a transformer 9.

To explain the basic operation of this embodiment, speed control is performed by adjusting the secondary current of the winding induction machine 1 through the on/off operation of the secondary chopper 3, and controlling the torque proportional to the secondary current of the winding induction machine 1. The secondary power of the induction machine 1 is charged to the capacitor 5 via the diode 4 when the secondary chopper 3 is off.

The voltage on capacitor 5 increases. Therefore, the voltage of the capacitor 5 is detected, and the on/off of the regenerative chopper 6 is controlled so that the voltage value is constant. In this way, the above-mentioned secondary power is transferred to the regenerative inverter 8 via the regenerative chopper 6.
It is further converted into AC power and regenerated into AC power supply.

Next, the control circuits for the secondary chopper 3 and the regenerative chopper 6 will be explained.

In the control circuit of the secondary chopper 6, first, the deviation between the signal of the speed command 13 and the output signal of the rotational speed detector 10 is amplified by the speed deviation amplifier 19,
Outputs the command signal 12 of the output current. The current detection signal it from the current detector 11 is compared in a comparator 17 with hysteresis, and an on/off control signal for the secondary chopper 3 is extracted. The signal is secondary chopper 3
The signal is amplified by the drive circuit 15, and the on/off of the secondary chopper 3 is controlled. As a result, the DC output current of the diode rectifier 2, the induction machine secondary current and the torque which are in a proportional relationship therewith are controlled by the above-mentioned IZ fist.The control circuit of the 6th order 1st regeneration chopper 6 will now be described. When the output signal of the comparator 17 is larger than 12 by a predetermined value Δi2 (hysteresis width), the output signal of the comparator 17 is “IJ,” conversely, Δil
When the signal becomes smaller than 0, the signal becomes "0", and when the signal is "1", the secondary chopper 3 is turned on, and when it is "0", the secondary chopper 3 is turned off.

The non-conducting ratio calculator 22 inverts the phase of the signal from the comparator 17 and calculates the average value thereof, thereby extracting a signal related to the non-conducting ratio (T OFF / T ). On the other hand, the slip calculation @21 uses the speed detection signal from the speed detector 10 to calculate the slip of the induction machine according to equation (1). Here, since the slip and the secondary voltage (sEzo) are proportional, the above-mentioned Veri calculation unit 21 and non-conduction ratio calculation unit 22
The capacitor voltage can be calculated and detected by dividing the output signal according to the above-mentioned equation (2).

From this, the deviation between the signal of the voltage command unit 14 and the capacitor voltage calculation signal is amplified by the voltage deviation amplifier 20,
A command signal ire for the current flowing through the regenerative inverter 8 is output. This j! The regenerative inverter current detection signal it from the umbrella and the current detector 12 are compared in a comparator 18 with hysteresis, and an on/off control signal for the regenerative chopper 6 is extracted. The signal is amplified by the drive circuit 16 of the regenerative chopper 6, and the on/off of the regenerative chopper 6 is controlled.

That is, the capacitor voltage detection signal is
4, the on-operation period of the regenerative chopper 6 increases. - Since the capacitor current also increases, the voltage of the capacitor 5 is controlled to a predetermined value.

Other embodiments of the present invention are shown in FIGS. 2 and 3, respectively.

In FIG. 2, when the AC power supply voltage fluctuates, that is, the primary voltage of the wound induction machine 1 fluctuates, the secondary voltage also fluctuates, so in the embodiment of FIG. An error occurs. This embodiment is designed to compensate for this. That is, the voltage detector 25 and transformer 26 in FIG. It is possible to detect the secondary voltage taking into account fluctuations in the voltage. This signal is divided by divider 2
3, it is possible to compensate for detection errors in capacitor voltage due to fluctuations in AC power supply voltage.

By the way, the secondary voltage of the wound induction machine 1 varies depending on the magnitude of the wind current of the diode rectifier 2 due to an internal voltage drop of the induction machine. The embodiment shown in FIG. 3 is a device designed to compensate for detection errors in capacitor voltage due to this influence. That is, the current detection signal from the current detector 11 is input to the function generator 27 to calculate the output voltage drop amount of the diode rectifier 2, and the output signal is used to calculate the output voltage drop of the diode rectifier 2.
By subtracting the output signal of 1, the effect of the voltage drop can be compensated for.

By the way, in the embodiment described above, the secondary current command signal 12*
In this method, the secondary chopper 3 is turned on and off when the deviation between the secondary current 12 and the secondary current 12 exceeds a predetermined value. However, the present invention is not limited to such a method, but can also be applied to the method described below, and similar operations can be performed. That is, the system adds the deviation between ip and 12 to a current deviation amplifier, compares the signal of the amplifier with the carrier wave that determines the on/off frequency of the secondary chopper 3 in a comparator, and extracts the on/off signal from the comparator.

The output signal of the current deviation amplifier in this case is a signal related to the conduction ratio of the secondary chopper 3, and it is clear that the capacitor voltage can be detected using the signal according to equation (2) as in the previous embodiment. .

Note that the axle 28 may be connected to the output side of the diode rectifier 2 and the input side of the regenerative inverter 8, or may be omitted. In that case, a single winding induction machine 1 or a transformer 9
The leakage inductance acts as a reactor.

〔Effect of the invention〕

According to the present invention, since the capacitor voltage detector can be omitted, there is no need for a detector which becomes more expensive as the capacitor voltage becomes higher, which is advantageous in terms of economy. Furthermore, since the detector that handles high voltage and other control circuits do not have to be installed separately, there is an effect that the device can be made smaller.

Furthermore, since there is no need to consider the problem of deterioration of the insulating material of the detector or its peripheral equipment, it is also effective in improving reliability.

[Brief explanation of drawings]

1 to 3 are configuration diagrams each showing an embodiment of the present invention. 1... Induction machine, 2... Diode rectifier, 3...
Secondary chopper, 4... Backflow blocking diode, 5...
Capacitor, 6... Regenerative chopper, 7... Freewheeling diode, 8... Regenerative inverter, 9... Transformer, 2
1... Slip calculator, 22... Non-conduction ratio calculator,
23...Divider.

Claims (1)

[Claims] 1. Connect an induction machine capable of secondary excitation, a secondary chopper for secondary current adjustment to the forward converter connected to the secondary side of the induction machine, and connect a capacitor and diode in parallel with the secondary chopper. In the device, a series circuit is connected, a regeneration chopper is connected to adjust the voltage of the capacitor, and an inverse converter is connected to convert the output to AC and regenerate the power from the capacitor to an AC power source. An induction machine characterized in that the voltage of the capacitor is calculated and detected using a signal related to the rotational speed of the induction machine and the conduction ratio of the secondary chopper, and the regenerative chopper is controlled so that the voltage of the capacitor becomes a predetermined value. Control device.