JPS5872341A - Reactive power compensating device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a reactive power compensator.

Voltage fluctuations occur in electrical systems connected to loads such as arc furnaces that generate irregularly fluctuating reactive power, which causes flicker. To avoid this, reactive power compensators (hereinafter referred to as compensation devices) ) will be installed.

FIG. 1 shows the configuration of a conventional compensation device of this type.

1 is an AC power supply, 2 is a power source impedance, 3 is an electrical system, 4 is a load, and 5 is a furnace transformer. Compensation device (in the figure -
Inside the imaginary chain) 100 is formed by connecting a transformer 11, a reactor 12, and a thyristor in antiparallel! Iristor circuit 13
A slow phase reactive power adjustment device 10 consisting of a capacitor 21
and a phase advance capacitor/filter device 20 consisting of a reactor 22 and a reactor 22. In addition, 30.4
0 are a fluctuation detection circuit and an ignition pulse generation circuit, respectively.

Furthermore, P'T is provided to detect the electric current voltage, and CT is provided to detect the load current, which are input to the respective detected voltage and current fluctuation detection circuits 30.

Now, the conventional device configured as described above has characteristics as shown in FIG. That is, the load 40 reactive current IQ
When I- becomes large, the so-called reactor current III flowing through the reactor 12 is reduced, and conversely, when the reactive current I of the load 4 becomes small, a large amount of the reactor current I- is made to flow, and the reactive power of the load 40 is constantly increased. 12
The phase of the firing pulse to the thyristor circuit 15 is controlled so that the sum of the reactive power and the reactive power of I'm trying to make it happen.

Therefore, from the perspective of flicker countermeasures, the reactor voltage f
ltII+1 is a shift from the conventional 50 yen because it is better to compensate for the reactive power of load 4 by controlling the current up and down around the rated 50 yen from the viewpoint of flicker improvement effect and effective use of the device. A circuit and an automatic dead band circuit are provided.

For example, the 51 shift circuit detects the reactor tg1ii@ and constantly performs feedback control with a certain time constant so that the electric current fiI- reaches the rated value of 50LIs. Therefore, the reactor current I- exhibits a characteristic that compensates for the reactive power of the load 40 around the rated value of 50 cm, regardless of the magnitude of the reactive power of the load 4.

Further, the automatic dead band circuit is a circuit that sets a dead band according to the base amount so as not to be sensitive to the base portion (reactive power that does not fluctuate) of the reactive power of the load 4. As a result, as described above, the reactor current XHg can be considered to be centered around the rated value of 50 Ou, and that of the load 4 to be around the rated value of 50 O.

is often selected to be equal to the lagging phase capacity of the reactor 12,
Therefore, in this case, the phase advance capacitor/filter device 20
The average reactive power of the compensation device 100 as a whole, which is the sum of the reactive power generated by the lagging reactive power adjusting device 10 and the reactive power generated by the lagging reactive power adjusting device 10, is the leading reactive power of the rated capacity o50.

That is, although the compensator 100 is installed to prevent flicker, it can also be used to improve power.

Flicker caused by fluctuating loads, especially flicker caused by arc furnaces, includes high-level flicker that occurs during the melting period and low-level flicker that occurs during the refining period. This difference in the flicker level is caused by the fluctuation of the reactive power (ΔQ), and is caused by the fact that during the melting period, this is large during the fluctuation of the reactive power, and during the refining period, this is small. Although there is a difference in the fluctuation of reactive power between the melting period and the refining period, the average reactive power is the same root as 1. In particular, in direct reduced iron furnaces, the period during which flicker occurs is 1c.
hargM 2 hours) during the first 10 minutes &[
The flicker level also reaches its peak value of 1 after this time period.
/6, and a low level of flicker occurs for most of the driving time.

Therefore, the main purpose of flicker countermeasures is to suppress high-level flicker, and there is no need to specifically suppress low-level flicker. As a device,
In addition, during the refining period when the 7 flicker level is low, the effect of flicker countermeasures is somewhat sacrificed (even if it is, the operating efficiency of the compensator is improved if it is mainly used as a phase advance capacitor device).

Regarding flicker countermeasures, high-level flicker countermeasures can be considered to have the same effect as conventional flicker countermeasures.

This invention was proposed based on the above circumstances, and
The purpose is to have the compensator function as a conventional flicker suppressor when the flicker level is high, while functioning primarily as a phase advance capacitor device when the flicker level is low. In addition to improving the reactor current, the current! The objective is to reduce the operating loss of this type of compensator by reducing R.

In order to achieve the above object, the present invention detects flicker or reactive power fluctuations or grid voltage fluctuations due to load fluctuations, and switches the operation of the compensator based on the detected signal.

Hereinafter, this invention will be explained in detail with reference to the drawings.

FIG. 6 shows an embodiment of the present invention.

In the figure, the same parts or equivalent parts as in the 1s1 figure are given the same reference numerals. The major difference from the conventional example shown in FIG. 1 is that a control circuit 50 is provided. This control circuit 50 is configured to be able to detect at least one of flicker detection, reactive power fluctuation detection, and voltage fluctuation detection. FIG. 4 is a block diagram showing a specific configuration of this control circuit 50. 51 is an input terminal into which a signal is input;
52 is a detection unit that includes at least one of a flicker detection circuit, a reactive power fluctuation detection circuit, or a voltage fluctuation detection circuit.
It is equipped with one. Reference numeral 53 denotes an average value circuit that calculates the average value of the detection signal obtained by the detection section 52, and is composed of a first-order lag type integrating circuit having a time constant of, for example, several tens of seconds to several minutes 11f. 54 is a constant circuit, and 55 is a comparison circuit, which compares the reference value from the reference value setting circuit 56 and the detection signal. 57
is a relay circuit. Note that 61 is an input terminal to which a bus voltage value and a load current value are input.

In the following section 8, a case will be described in which the flicker level is determined and the operation of the compensator 100 is switched based on this determination.

In this case, a flicker level signal f from a flicker meter (not shown) is applied to the input terminal 51.

Therefore, the detection section 52 is omitted. A reference flicker level f8, which is a switching level for device functions, is set in the reference value setting circuit 56. The flicker level signal f that has passed through the input terminal 51 is input to the average value circuit 55, where it is averaged (its value is T).The flicker level signal f is compared with the reference flicker level fs in the comparator circuit 55, and the flicker level signal f) is averaged (its value is T). In some cases, the compensation device 100 acts as a flicker suppression device for the purpose of flicker improvement. On the other hand, when f(fs,
((As shown in 11, the compensation device 100 mainly functions as a phase advance capacitor device.

@R in Figure 5, ■ is the characteristic line of the reactive power generated by the accelerator 12 when the compensator 100 functions as a flicker suppression device, and ■ is the characteristic line when the 10 compensators mainly function as a phase advance capacitor + device. The reactive power characteristic straight line generated by the accelerator 12, ■ is a line representing the average reactive power generated by the reactor 12 when the compensator f100 functions as a flicker suppressor, and W is a line representing the average reactive power generated by the reactor 12 when the compensator f100 functions as a flicker suppressor. This is a straight line representing the average reactive power generated by the actuator 12 when it functions.

FIG. 5 (at is the case where the flicker level is low,
The immersion pulse to the thyristor circuit 13 is stopped, and the reactor current Imw is reduced to zero, which is aimed at improving the power factor. Therefore, it contributes to improving the power factor of the electrical system 6 by 50 times more than the rated value compared to the conventional case.

FIG. 5 (blc) When the flicker level is low,
This figure shows the case where the ignition pulse to the thyristor circuit 13 is narrowed down to a certain constant phase, and a constant torque current tItIIs is passed through the reactor 12 at the rated Oq% (<50 minutes). In this case, the compensation device 100
The phase-advanced reactive power generated from the rated power is generated by (50-q) 1 minute more than the rated value, and this amount contributes to improving the power factor of the electrical system 5.

FIG. 5 (cl is the case where the flicker level is low,
In this case, the characteristics when the compensator 100 functions as a 7-resistance suppressor are directly changed to the smaller reactor voltage aI-, which indicates the case where the immersion pulse to the thyristor circuit 16 is fixed or stopped. The load 4 is made to have characteristics that can compensate for the reactive power generated by the load 4 to some extent. However, its average reactive power is q% (<5
0(i) seconds, on average, as in the case of the direction shown in FIG. It is assumed that a large amount of power is generated, and this amount contributes to improving the power factor.

On the other hand, if the flicker level is high, the compensation device 100
functions as a flicker suppressor, just like before.
The flicker improvement effect is the same as before.

FIG. 6 shows the flicker improvement effect of this compensator based on Tsumei in comparison with that of the conventional O compensator.

Figure 6 (&1 represents the temporal transition of the flicker generation level of the load, and Figure 6 (bl represents the flicker level after countermeasures using the conventional compensation device)
-, in Fig. 6 (61 is the output of the pricker level signal by the compensator according to the above).

In general, the flicker level is evaluated as the 95th value of a normal distribution, so even if flicker countermeasures are made only in areas with high υ other than flicker, the evaluation will not change.As can be understood from Figure 6, the conventional Thus, even if flicker countermeasures are taken for all time periods, or even if flicker measures are taken only for high flicker time periods as in the present invention, the flicker level can be said to vary to the same extent.

From the above, according to this invention, ■ Flicker suppression effect remains the same as before.

■ The operating power factor of the load is improved compared to before.

■ From ■, it may be possible to reduce the capacitance of the power factor correction capacitor that has been conventionally provided on the load side for power factor correction. Also, for newly installed loads.

The capacity of the phase advance capacitor for power factor improvement can be small.

■ The capacity of the compensation device itself remains the same as before.

In addition to the above effects, the control circuit 50 of the present invention can be easily added to a conventional compensator of this type.

In the above description, a case has been described in which the abnormal operation is switched to lJf at the flicker level, but the following signals other than flicker can be considered as signals for switching determination.

■ The average level of the load's reactive power fluctuation (△Q) is used as the operation switching signal. Generally, the pricker level is proportional to the reactive power fluctuation (ΔQ) of the load. In other words, the larger the reactive power fluctuation, the higher the flicker level.The average level of second reactive power fluctuation is detected, and this is compared with a reference level.If the fluctuation is large, the flicker suppression device is used.
If it is small, the compensation device mainly functions as a phase advance capacitor device. In this case, part of the configuration of the control circuit 50 shown in FIG. 4 is changed as follows. That is, the input terminal 51 receives the system's bus voltage deficiency and the load current, a reactive power detection circuit that outputs a DC signal is used as the detection unit 52, and a reference value setting circuit 56 receives the reactive power fluctuation level. is set.

The average level of the voltage fluctuation (ΔV) during OW4 is used as the operation switching signal. This is also the same as above, the instantaneous voltage f movement (Δ
V), this variation (ΔV) is detected and the operation is switched.

In this case, a part of the configuration of the control circuit 50 shown in FIG. A voltage fluctuation detection circuit is used, and a voltage fluctuation level is further set in the reference value setting circuit 56.Alternatively,
The voltage fluctuation output signal of the pritzkameter is input to the input terminal 51, the detection section 52 is omitted, and the voltage fluctuation level is set in the reference value setting circuit 56.

[Brief explanation of drawings]

Fig. 1 is a single line diagram showing a conventional device, Fig. 2 is an operating characteristic diagram of the conventional device, Fig. 3 is a single line diagram of a device according to the present invention, Fig. 4 is a block diagram showing the configuration of main parts, Figure 5, j
Figure g6 is an operating characteristic diagram. 4... Load, 100... Patent applicant for reactive power compensator Nissin Electric Co., Ltd. Representative Director and President Tadashi Yamawaki Katsuhiro 1 Oichi'X Z Figure □IQL A 3 InTt ) Hikoichi + JQL IQL →lQt

Claims (1)

[Claims] In a device that compensates for reactive power due to load fluctuations, it detects flicker caused by load fluctuations, reactive power fluctuations, or voltage fluctuations and functions primarily as a continuous phase condenser based on the detected signal. Characteristic reactive power compensator.