JPS6290718A - Control system for reactive power compensator - Google Patents

Abstract

PURPOSE:To make the distinctive feature of high-speed control useful and, at the same time, to obtain the effect of power-factor compensation, by further adding closed- loop control for making power-factor compensation to open-loop control. CONSTITUTION:Signals outputted from reference circuits 24a, 24b, and 24c are the aimed values of power-factor control and by taking the differences between the aimed values and feedback signals outputted from delaying circuits 22a, 22b, and 22c deviated quantities of the control are outputted from difference points 23a, 23b, and 23c. Ampli fier circuits 25a, 25b, and 25c amplify the deviating quantities and input the amplified quantities to difference points 26a, 26b, and 26c between the function converting circuits 6a, 6b, and 6c and ignition angle control circuits 7a, 7b, and 7c of open-loop control. The deviating quantities are further inputted to the ignition angle control circuits 7a, 7b, and 7c from the difference points 26a, 26b, and 26c and an electric current is made to flow to thyristors 8 and 9 by triggering the gates of the thyristors with the outputs of the control circuits 7a, 7b, and 7c. Therefore, a stationary reactive power compensator 100 compensates the reactive power fluctuation of an arc furnace 2 and, at the same time, can compensate the power-factor of a power system.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention compensates for four reactive forces of a fluctuating load by a combination of a compensation reactor and a compensation capacitor whose phase is controlled by a thyristor connected in parallel with the fluctuating load in a power system. Invalid '1. Control force formula of force compensator % formula % [Technical background of the invention and its problems] A load that generates irregular and drastically fluctuating reactive power, such as an r-ri furnace, is connected. 4. In power systems, voltage fluctuations occur due to fluctuations in reactive power, and
4-pressure flicker occurs. A reactive power compensator is installed to suppress this.

FIG. 2 is a control block diagram and a single line diagram of a conventional thyristor-controlled compensating reactor reactive force compensator.

In the figure, R is a furnace transformer, 2 is an arc furnace, 3 is a current transformer, 4 is a transformer, 5 is a reactive power detection circuit, 6 is a function conversion circuit, and T is a firing angle control circuit. be. 8 and 9 are thyristors, 10 is a compensation reactor, 11 is a compensation capacitor, 1
00 is a static non-dynamic power compensator.

The reactive power generated by the r-ri furnace 2, which is a variable load, is
A current transformer 3 detects a current, a transformer 4 detects a voltage, and these are added to an invalid loop detection circuit 5 to detect four invalid loops.

This output is input to the function conversion circuit 6, which outputs a phase control signal. Here, in order to compensate for the reactive power generated in the arc furnace 2, a phase control signal for the nurse r9 star 8.9 is output. This output is input to the firing angle control circuit 7, and a P-) signal is output to the thyristor 8.9.

? The explanation in Figure 82 is written using a single line, but in the case of an arc furnace load, since it is a three-phase unbalanced load, the reactive power is detected individually for each phase, and a function conversion circuit 6 is provided for each phase. It is necessary for each firing angle control circuit 7 to determine the firing phase angle of the thyristor. In order to suppress flicker caused by reactive force fluctuations in an arc furnace, a reactive gravity compensator with a high-speed response control method is required. An open-loop controlled reactive power compensation mid was used to compensate the corresponding reactive power. However, since it is an open-loop control, the control accuracy deteriorates, resulting in a poor power factor.

[Departure (man's purpose)]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and to solve the problem of invalid 'Ifl
An object of the present invention is to provide a control system for a reactive power compensator capable of compensating for the total degree of power fluctuation and also compensating for the power factor of a power system.

[Summary of the invention]

In order to achieve this objective, the present invention adds open-loop control for power factor compensation to conventional open-loop control for high-speed control, takes advantage of the characteristics of high-speed control, and takes advantage of the effects of power factor compensation. It is characterized by the fact that it also takes advantage of

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. 1, 12 is a current transformer, 2
1 is a reactive power detection circuit, 22 is a delay circuit, 23 is a subtraction point, 24 is a reference circuit, 25 is a boosting circuit, and 26 is a subtraction point. Furthermore, Nafix a, l),
Let c be 1, which is used to express the three phases individually, and let 101 be the three-phase control circuit. Otherwise, the same numbers as in FIG. 2 indicate the same parts.

The operation of the present invention will be explained below. Since the open-loop control has been described previously, it will be omitted, and the closed-loop control will be described. A current composite value of the arc furnace 2 and the static non-dynamic magnetic force compensator 1oo is detected by the current transformer 12.

The magnetic current signal and the secondary pressure and pressure of the transformer 4 (7) are input to reactive power detection circuits 21a, 21b, and 21c. An example of the input/output characteristics of this reactive power detection circuit is shown in FIG.

That is, a signal proportional to reactive power is output. This signal is input to delay circuits 22a, 22b, and 22c. .

The delay circuits 22a, 22b, and 22c output human power (No. 8) with a certain time constant. This is to avoid giving.

That is, this is to ensure that when the open-loop control side signal and the closed-loop control side signal operate in opposite directions, the open-loop control side signal takes priority.1. Although high-speed response control is required to suppress flicker, power factor control does not cause any problem even if the response speed is slightly slower than flicker suppression control. Delay circuit 22a t 22b.

22c output and reference circuits 24a, 24b, 24
Subtract the output signal from c to points Z3a, 23b,
Take the difference at 23C and increase - times 1125a, 25b
, 25c.

The signals output from the reference circuits 24a, 24b, and 24c are target values for power factor control, and the signals output from the reference circuits 24a, 24b, and 24c are the target values for power factor control, and
22b.

By taking the difference from the feedback signal output from 22c, the control deviation is subtracted from point 23a.

It is output from 23b and 23c. Masu 1 crystal episode d25a
, 25b.

In 25c, the deviation is increased, and the conventional open loop control function conversion circuits 6a, 6b, 6c and firing angle control circuit 7a.

Subtraction points 26a, 26b between 7b and 7c,
26c. Furthermore, deduction point 26a,
26b, 26c to firing angle control ports d7a, 7b, 7
This output triggers the dart of thyristor 8.9 and causes Nst to flow through the thyristor. In Fig. 1, the main circuit part is a three-phase circuit, but it is a single wire connection, and the control circuit 101
is expressed as a three-phase circuit consisting of one person. This method of expression was used especially to show that the closed loop control is not a three-phase integrated circuit but a three-phase individual control.

This is because the arc furnace is generally a three-phase unbalanced load, and it is necessary to apply open-loop control and closed-loop control to each phase separately7.Therefore, the static passive power compensator 100 In addition to compensating for reactive power fluctuations, it is also possible to compensate for the power factor of a dual-power system.

〔Effect of the invention〕

As explained above, according to the present invention, not only can flicker of the arc furnace 2 be suppressed by high-speed control, but also the overall power factor compensation effect of the arc furnace and the static non-dynamic power compensator can be achieved. is obtained.

[Brief explanation of drawings]

Fig. 1 is a control block diagram and single-line connection diagram of a reactive power compensation device showing an embodiment of the present invention, Fig. 2 is a control block diagram and single-line connection diagram of a conventional reactive power compensation device, and Fig. 3 is the first
The reactive power detection circuit 21a shown in the figure. The input/output characteristics diagram of 21b and 21c is ■... Furnace transformer, 2... Arc furnace, 3... Transformer i>tt transformer,
11... Transformer, 5... Reactive power detection circuit, 6...
・Function conversion circuit, 7... Firing angle control circuit, 8.9...
・Nairista, 10... Compensation vector. 11... Compensation capacitor, 12... Current transformer, 5a,
5b, 5c... Invalid single force detection circuit 6a, 6b,
6c...Function conversion circuit 7 a, 7. b, 7 e
... Firing angle control circuits 21a, 21b, 21c...
- Reactive power detection circuits 22a, 22b, 22C...delay circuits 23a, 23h, 23c, 2Ga, 2
6h, 26c・” points 24a, 24b,
24cm reference circuit 25a, 25b, 25cm increase] Elephant circuit 100...Static invalid force extraction device 101...Control circuit agent Patent attorney Noriyuki Chika Superposition Hirofumi Mitsumata Figure 1 Figure 2

Claims (1)

[Claims] In a reactive power compensation device in which a compensation reactor and a compensation capacitor are provided in parallel between a power system and a variable load in order to compensate for reactive power generated by a variable load, and the phase of the current flowing through the compensation reactor is controlled by a thyristor,
an open-loop control system for suppressing flicker caused by reactive power fluctuations of the variable load; and a closed-loop control system for compensating the power factor of the power system, the control response of which is slower than the open-loop control system; A control method for a reactive power compensator, characterized in that the closed loop control system is controlled individually for three phases, and the reactive power compensator is controlled by both of these control systems.