JPH09229560A - Method for controlling flicker-restraining apparatus for arc furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power loss while restraining flicker by changing over a maximum output capacity of a flicker restraining apparatus in response to the operation conditions of an arc furnace. SOLUTION: A flicker restraining apparatus for an arc furnace comprises a high-impedance transformer 4, a thyristor transducer 5, a reactive power detector 6, a flicker controlling circuit 14, setters 11 to 13 and a change-over circuit 10. The change-over circuit 10 detects a flicker fluctuation width generated by the operation of the arc furnace 2 on the basis of an output from the reactive power detector 6. According to this detection, either one of set values by the setters 11 to 13 is selected to be inputted into the flicker controlling circuit 14, and, on the basis of the control made by the flicker controlling circuit 14, flicker is restrained within a range up to a capacity based on the set value at which a maximum output capacity of the thyristor transducer 5 is selected by the setters 11-13. By this method, a maximum output capacity of the flicker restraining apparatus for the arc furnace can be changed over in response to a boring period, a melting period, and an oxidation and reduction period in the arc furnace 2, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling an flicker suppressing device for an arc furnace, which suppresses flicker generated by the operation of an arc furnace.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional arc furnace facility of this type. 1 is a transformer for a furnace including a load tap changer, 2 is an arc furnace, 2a is an electrode, 3 is an electrode. A phase-advancing capacitor for improving the power factor of this arc furnace equipment, 4 is a high impedance transformer, 5 is a thyristor converter connected to the secondary winding of the high impedance transformer 4, and 6 is reactive power detection of the arc furnace 2. Reference numeral 7 is a flicker control circuit that outputs a gate signal of the thyristor converter 5 to suppress flicker of the arc furnace 2, and 8 is a setting device that sets the maximum output capacity of the thyristor converter 5.

In FIG. 3, the flicker suppressing device for an arc furnace comprises a high impedance transformer 4, a thyristor converter 5, a reactive power detector 6, a flicker control circuit 7 and a setting device 8. Fluctuation of the reactive power flowing into the arc furnace equipment from the illustrated power system by controlling the firing phase of the equivalent reactor of the high impedance transformer 4 and the thyristors of the thyristor converters 5 in order to suppress the generated flicker. Is being reduced.

FIG. 4 is a waveform diagram showing a control method of a conventional flicker suppressing device for an arc furnace. When the fluctuation range of the reactive power Q _F (see FIG. 3) flowing into the arc furnace 2 shown in FIG. 4 (a) is 100%, the output capacity Q _L (see FIG. 3) of the flicker suppressing device for an arc furnace is As shown in FIG. 4B, the operation is performed so as to suppress the flicker generated by the operation of the arc furnace 2 while changing up to 100%.
As shown in (c), fluctuations of reactive power (Q _F + Q _L ) flowing from the power supply system (see FIG. 3) into the arc furnace facility, that is, flicker is suppressed.

Further, for example, the arc furnace 2 shown in FIG.
Fluctuation range of reactive power Q _F (see Fig. 3) flowing into
In the case of, the output capacity Q of the flicker suppression device for arc furnace
_As shown in FIG. 4B, _L (see FIG. 3) operates so as to suppress flicker generated by the operation of the arc furnace 2 while changing up to 100%, and as a result, as shown in FIG. 4C. Fluctuation of the reactive power (Q _F + Q _L ) that flows into this arc furnace facility from the power supply system (see FIG. 3), that is, flicker is suppressed.

[0006]

According to the conventional control method for the flicker suppressing device for an arc furnace described above, the maximum output capacity of the flicker suppressing device for an arc furnace is set in FIG. 3 regardless of the operating state of the arc furnace 2. Since the set value of the setter 8 is constant, the arc furnace 2 shown in FIG.
Even if the fluctuation range of the reactive power Q _F flowing in is 50%,
The output capacity Q _L of the flicker suppression device for arc furnace is shown in Fig. 4.
As shown in (b), it changes up to 100%, and as a result, as shown in FIG. 4 (c), the reactive power (Q _F + Q _L ) flowing into this arc furnace facility from the power supply system (see FIG. 3) is also 100%.
There is a problem that the electric power loss of this arc furnace equipment is large because the value is in the vicinity.

An object of the present invention is to provide a control method of an flicker suppressing device for an arc furnace which solves the above problems.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for controlling an flicker suppressing device for an arc furnace which suppresses flicker caused by the operation of the arc furnace, and a flicker suppressing device for an arc furnace according to the operating state of the arc furnace. Switch the maximum output capacity of. According to the present invention, a boring period in which the arc furnace starts flowing and an arc is generated in a state where an electrode digs a hole and descends, a melting period until the scrap is completely melted after the boring is completed, and scrap is completely removed. Oxidation and reduction periods in the state of being dissolved in water and the operating state change every moment, and the amount of flicker generated in these operating states is also
Generally, there is a relation of boring period> melting period> oxidation and reduction period, so it is possible to switch the maximum output capacity of the arc furnace flicker suppressing device according to the operating state of the arc furnace. The power loss of the arc furnace equipment can be reduced.

[0009]

1 is a block diagram of an arc furnace facility showing an embodiment of a control method for an flicker suppressing device for an arc furnace according to the present invention, which has the same function as the conventional example shown in FIG. The same reference numerals are given to the components, and the description thereof will be omitted. That is, in FIG. 1, the flicker suppressing device for an arc furnace includes a high impedance transformer 4, a thyristor converter 5, a reactive power detector 6, a flicker control circuit 14, and a setter 11.
13 to 13 and the switching circuit 10, the switching circuit 10 detects the fluctuation range of the flicker generated by the operation of the arc furnace 2 from the output of the reactive power detector 6, and detects the fluctuation range of each of the setters 11 to 13 from this fluctuation range. One of the set values is selected and input to the flicker control circuit 14,
By the control of 1), the maximum output capacity of the thyristor converter 5 operates to suppress flicker within a range up to the capacity of the set value selected by any one of the setters 11 to 13.

FIG. 2 is a waveform diagram showing a method of controlling the flicker suppressing device for an arc furnace according to the present invention. The fluctuation of the reactive power Q _F (see FIG. 1) flowing into the arc furnace 2 shown in FIG. When the width is 100%, for example, the setting device 11 is selected by the switching circuit 10 and the output capacity Q _L (see FIG. 1) of the flicker suppressing device for an arc furnace is up to 100% as shown in FIG. While changing, it operates so as to suppress the flicker generated by the operation of the arc furnace 2, and as a result, FIG.
As shown in (c), the reactive power (Q _F + Q _L ) that flows into this arc furnace equipment from the power supply system (see FIG. 1) also maintains a value near 100%, while suppressing the flicker of this arc furnace equipment, In this case, the operation is similar to that of the conventional example shown in FIG.

Further, for example, the arc furnace 2 shown in FIG.
Fluctuation range of reactive power Q _F (see Fig. 1) flowing into
In the case of, for example, the setting device 13 is selected by the switching circuit 10, and the output capacity Q of the flicker suppressing device for an arc furnace is selected.
_As shown in FIG. 2C, _L (see FIG. 1) operates to suppress flicker generated by the operation of the arc furnace 2 while changing up to 50% as shown in FIG. 2B. reactive power flowing from the power supply system (see FIG. 1) to the arc furnaces (Q _F + Q _L) while maintaining the value of around 50%, thereby suppressing flicker of the arc furnace facilities.

In the embodiment of the present invention, the three setting devices 11 to 13 are switched by the switching circuit 10 by detecting the fluctuation range of the flicker generated by the operation of the arc furnace 2 from the output of the reactive power detector 6. Therefore, it is preferable to correspond to each of the above-mentioned boring period, dissolution period, oxidation, and reduction period. Further, the boring period, the melting period, the oxidation period, and the reduction period have substantially constant time intervals depending on the operation mode of the arc furnace, so that the function of the switching circuit can be configured by a timer.

[0013]

According to the present invention, by switching the maximum output capacity of the flicker suppressing device for an arc furnace according to the operating state of the arc furnace, the flicker of the arc furnace equipment is suppressed and the power loss of this arc furnace equipment is reduced. Can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an arc furnace facility showing an embodiment of a control method of an flicker suppressing device for an arc furnace of the present invention.

FIG. 2 is a waveform chart illustrating the operation of FIG.

FIG. 3 is a block configuration diagram of an arc furnace facility showing a conventional example of a control method of an flicker suppressing device for an arc furnace.

FIG. 4 is a waveform chart for explaining the operation of FIG. 3;

[Explanation of symbols]

1 ... Reactor transformer, 2 ... Arc furnace, 2a ... Electrode, 3 ... Phase advancing capacitor, 4 ... High impedance transformer, 5 ... Thyristor converter, 6 ... Reactive power detector, 7, 14 ... Flicker control circuit, 8, 11 to 13 ... Setting device, 10 ... Switching circuit.

Claims (1)

[Claims] 1. A method of controlling an flicker suppressing device for an arc furnace, which suppresses flicker generated by the operation of an arc furnace, wherein the maximum output capacity of the flicker suppressing device for an arc furnace is switched according to the operating state of the arc furnace. Control method for flicker suppression device for arc furnace.